DISPATCH M. Miller Internet-Draft Obsoletes: 4329 (if approved) M. Borins Intended status: Informational GitHub Expires: 15 April 2022 M. Bynens Google B. Farias 12 October 2021 ECMAScript Media Types Updates draft-ietf-dispatch-javascript-mjs-10 Abstract This document describes the registration of media types for the ECMAScript and JavaScript programming languages and conformance requirements for implementations of these types. This document obsoletes RFC4329, "Scripting Media Types", replacing the previous registrations for "text/javascript" and "application/javascript" with information and requirements aligned with implementation experiences. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 15 April 2022. Copyright Notice Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights Miller, et al. Expires 15 April 2022 [Page 1] Internet-Draft ECMAScript Media Types Updates October 2021 and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. Charset Parameter . . . . . . . . . . . . . . . . . . . . 5 4.2. Character Encoding Scheme Detection . . . . . . . . . . . 5 4.3. Character Encoding Scheme Error Handling . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 6.1. Common JavaScript Media Types . . . . . . . . . . . . . . 10 6.1.1. text/javascript . . . . . . . . . . . . . . . . . . . 10 6.2. Historic Javascript Media Types . . . . . . . . . . . . . 11 6.2.1. application/ecmascript . . . . . . . . . . . . . . . 11 6.2.2. application/javascript . . . . . . . . . . . . . . . 12 6.2.3. application/x-ecmascript . . . . . . . . . . . . . . 13 6.2.4. application/x-javascript . . . . . . . . . . . . . . 14 6.2.5. text/ecmascript . . . . . . . . . . . . . . . . . . . 15 6.2.6. text/javascript1.0 . . . . . . . . . . . . . . . . . 16 6.2.7. text/javascript1.1 . . . . . . . . . . . . . . . . . 17 6.2.8. text/javascript1.2 . . . . . . . . . . . . . . . . . 18 6.2.9. text/javascript1.3 . . . . . . . . . . . . . . . . . 19 6.2.10. text/javascript1.4 . . . . . . . . . . . . . . . . . 20 6.2.11. text/javascript1.5 . . . . . . . . . . . . . . . . . 21 6.2.12. text/jscript . . . . . . . . . . . . . . . . . . . . 22 6.2.13. text/livescript . . . . . . . . . . . . . . . . . . . 23 6.2.14. text/x-ecmascript . . . . . . . . . . . . . . . . . . 23 6.2.15. text/x-javascript . . . . . . . . . . . . . . . . . . 24 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 7.1. Normative References . . . . . . . . . . . . . . . . . . 25 7.2. Informative References . . . . . . . . . . . . . . . . . 26 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 27 Appendix B. Changes from RFC 4329 . . . . . . . . . . . . . . . 27 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28 Miller, et al. Expires 15 April 2022 [Page 2] Internet-Draft ECMAScript Media Types Updates October 2021 1. Introduction This memo describes media types for the JavaScript and ECMAScript programming languages. Refer to the sections "Introduction" and "Overview" in [ECMA-262] for background information on these languages. This document updates the descriptions and registrations for these media types to reflect existing usage on the Internet, and provides up-to-date security considerations. This document replaces the media types registrations in [RFC4329], and updates the requirements for implementations using those media types defined in [RFC4329] based on current existing practices. As a consequence, this document obsoletes [RFC4329]. 1.1. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 2. Compatibility This document defines equivalent processing requirements for the types text/javascript, text/ecmascript, and application/javascript. The most widely supported media type in use is text/javascript; all others are considered historical and obsolete compared to text/ javascript. The types defined in this document are applicable to scripts written in [ECMA-262]. Later editions of [ECMA-262] are not directly addressed, although it is expected that implementations will behave as if applicability were extended to them. This document does not address other extensions to [ECMA-262] or scripts written in other languages. This document may be updated to take other content into account. Updates of this document may introduce new optional parameters; implementations MUST consider the impact of such an update. The definitions in this document reflect the current state of implementation across the JavaScript ecosystem, in web browsers and other environments such as Node.js alike, in order to guarantee backwards compatibility with existing applications as much as possible. Miller, et al. Expires 15 April 2022 [Page 3] Internet-Draft ECMAScript Media Types Updates October 2021 3. Modules In order to formalize support for modular programs, [ECMA-262] (starting with 6th Edition) defines two top-level goal symbols (or roots to the abstract syntax tree) for the ECMAScript grammar: Module and Script. The Script goal represents the original structure where the code executes in the global scope, while the Module goal represents the module system built into ECMAScript starting with 6th Edition. See the section "ECMAScript Language: Scripts and Modules" of [ECMA-262] for details. This separation means that (in the absence of additional information) there are two possible interpretations for any given ECMAScript source text. The TC39 standards body for ECMAScript has determined that media types are outside of their scope of work [TC39-MIME-ISSUE]. It is not possible to fully determine if a source text of ECMAScript is meant to be parsed using the Module or Script grammar goals based upon content alone. Therefore, scripting environments use out of band information in order to determine what goal should be used. Some scripting environments have chosen to adopt the file extension of .mjs for this purpose. This document does not define how fragment identifiers in resource identifiers ([RFC3986], [RFC3987]) for documents labeled with one of the media types defined in this document are resolved. An update of this document may define processing of fragment identifiers. 4. Encoding Refer to [RFC6365] for a discussion of terminology used in this section. Source text (as defined in [ECMA-262], section "Source Text") can be binary source text. Binary source text is a textual data object that represents source text encoded using a character encoding scheme. A textual data object is a whole text protocol message or a whole text document, or a part of it, that is treated separately for purposes of external storage and retrieval. An implementation's internal representation of source text is not considered binary source text. Implementations need to determine a character encoding scheme in order to decode binary source text to source text. The media types defined in this document allow an optional charset parameter to explicitly specify the character encoding scheme used to encode the source text. Miller, et al. Expires 15 April 2022 [Page 4] Internet-Draft ECMAScript Media Types Updates October 2021 How implementations determine the character encoding scheme can be subject to processing rules that are out of the scope of this document. For example, transport protocols can require that a specific character encoding scheme is to be assumed if the optional charset parameter is not specified, or they can require that the charset parameter is used in certain cases. Such requirements are not considered part of this document. Implementations that support binary source text MUST support binary source text encoded using the UTF-8 [RFC3629] character encoding scheme. Module goal sources MUST be encoded as UTF-8, all other encodings will fail. Source goal sources SHOULD be encoded as UTF-8; other character encoding schemes MAY be supported, but are discouraged. Whether U+FEFF is processed as a Byte Order Mark (BOM) signature or not depends on the host environment, and is not considered part of this document. 4.1. Charset Parameter The charset parameter provides a means to specify the character encoding scheme of binary source text. Its value SHOULD be a registered charset [CHARSETS], and is considered valid if it matches the mime-charset production defined in [RFC2978], section 2.3. The charset parameter is only used when processing a Script goal source; Module goal sources MUST always be processed as UTF-8. 4.2. Character Encoding Scheme Detection It is possible that implementations cannot interoperably determine a single character encoding scheme simply by complying with all requirements of the applicable specifications. To foster interoperability in such cases, the following algorithm is defined. Implementations apply this algorithm until a single character encoding scheme is determined. 1. If the binary source text is not already determined to be using a Module goal and starts with a Unicode encoding form signature, the signature determines the encoding. The following octet sequences, at the very beginning of the binary source text, are considered with their corresponding character encoding schemes: Miller, et al. Expires 15 April 2022 [Page 5] Internet-Draft ECMAScript Media Types Updates October 2021 +------------------+----------+ | Leading sequence | Encoding | |------------------+----------| | EF BB BF | UTF-8 | | FF FE | UTF-16LE | | FE FF | UTF-16BE | +------------------+----------+ Implementations of this step MUST use these octet sequences to determine the character encoding scheme, even if the determined scheme is not supported. If this step determines the character encoding scheme, the octet sequence representing the Unicode encoding form signature MUST be ignored when decoding the binary source text. 2. If a charset parameter is specified and its value is valid and supported by the implementation, the value determines the character encoding scheme. 3. If no other character encoding scheme is determined from the previous steps, it is assumed to be UTF-8. If the character encoding scheme is determined to be UTF-8 through any means other than step 1 as defined above and the binary source text starts with the octet sequence EF BB BF, the octet sequence is ignored when decoding the binary source text. 4.3. Character Encoding Scheme Error Handling Binary source text that is not properly encoded for the determined character encoding can pose a security risk, as discussed in section 5. That said, because of the varied and complex environments scripts are executed in, most of the error handling specifics are left to the processors. The following are broad guidelines that processors follow. If binary source text is determined to have been encoded using a certain character encoding scheme that the implementation is unable to process, implementations can consider the resource unsupported (i.e., do not decode the binary source text using a different character encoding scheme). Binary source text can be determined to have been encoded using a certain character encoding scheme but contain octet sequences that are not valid according to that scheme. Implementations can substitute those invalid sequences with the replacement character U+FFFD (properly encoded for the scheme), or stop processing altogether. Miller, et al. Expires 15 April 2022 [Page 6] Internet-Draft ECMAScript Media Types Updates October 2021 5. Security Considerations Refer to [RFC3552] for a discussion of terminology used in this section. Examples in this section and discussions of interactions of host environments with scripts, modules, and extensions to [ECMA-262] are to be understood as non-exhaustive and of a purely illustrative nature. The programming language defined in [ECMA-262] is not intended to be computationally self-sufficient, rather it is expected that the computational environment provides facilities to programs to enable specific functionality. Such facilities constitute unknown factors and are thus considered out of the scope of this document. Derived programming languages are permitted to include additional functionality that is not described in [ECMA-262]; such functionality constitutes an unknown factor and is thus considered out of the scope of this document. In particular, extensions to [ECMA-262] defined for the JavaScript programming language are not discussed in this document. Uncontrolled execution of scripts can be exceedingly dangerous. Implementations that execute scripts MUST give consideration to their application's threat models and those of the individual features they implement; in particular, they MUST ensure that untrusted content is not executed in an unprotected environment. Module scripts in ECMAScript can request the fetching and processing of additional scripts, called importing. Implementations that support modules need to process imported sources in the same way as scripts. Further, there may be additional privacy and security concerns depending on the location(s) the original script and its imported modules are obtained from. For instance, a script obtained from "host-a.example" could request to import a script from "host- b.example", which could expose information about the executing environment (e.g., IP address) to "host-b.example". See the section "ECMAScript Language: Scripts and Modules" in [ECMA-262] for details. Specifications for host environment facilities and for derived programming languages should include security considerations. If an implementation supports such facilities, the respective security considerations apply. In particular, if scripts can be referenced from or included in specific document formats, the considerations for the embedding or referencing document format apply. Miller, et al. Expires 15 April 2022 [Page 7] Internet-Draft ECMAScript Media Types Updates October 2021 For example, scripts embedded in application/xhtml+xml [RFC3236] documents could be enabled through the host environment to manipulate the document instance, which could cause the retrieval of remote resources; security considerations regarding retrieval of remote resources of the embedding document would apply in this case. This circumstance can further be used to make information, that is normally only available to the script, available to a web server by encoding the information in the resource identifier of the resource, which can further enable eavesdropping attacks. Implementation of such facilities is subject to the security considerations of the host environment, as discussed above. The programming language defined in [ECMA-262] does include facilities to loop, cause computationally complex operations, or consume large amounts of memory; this includes, but is not limited to, facilities that allow dynamically generated source text to be executed (e.g., the eval() function); uncontrolled execution of such features can cause denial of service, which implementations MUST protect against. With the addition of SharedArrayBuffer objects in ECMAScript version 8, it could be possible to implement a high-resolution timer which could lead to certain types of timin`g and side-channel attacks (e.g., [SPECTRE]). Implementations can take steps to mitigate this concern, such as disabling or removing support for SharedArrayBuffer objects, or take additional steps to ensure access to this shared memory is only accessible between execution contexts that have some form of mutual trust. A host environment can provide facilities to access external input. Scripts that pass such input to the eval() function or similar language features can be vulnerable to code injection attacks. Scripts are expected to protect against such attacks. A host environment can provide facilities to output computed results in a user-visible manner. For example, host environments supporting a graphical user interface can provide facilities that enable scripts to present certain messages to the user. Implementations MUST take steps to avoid confusion of the origin of such messages. In general, the security considerations for the host environment apply in such a case as discussed above. Implementations are required to support the UTF-8 character encoding scheme; the security considerations of [RFC3629] apply. Additional character encoding schemes may be supported; support for such schemes is subject to the security considerations of those schemes. Miller, et al. Expires 15 April 2022 [Page 8] Internet-Draft ECMAScript Media Types Updates October 2021 Source text is expected to be in Unicode Normalization Form C. Scripts and implementations MUST consider security implications of unnormalized source text and data. For a detailed discussion of such implications refer to the security considerations in [RFC3629]. Scripts can be executed in an environment that is vulnerable to code injection attacks. For example, a CGI script [RFC3875] echoing user input could allow the inclusion of untrusted scripts that could be executed in an otherwise trusted environment. This threat scenario is subject to security considerations that are out of the scope of this document. The "data" resource identifier scheme [RFC2397], in combination with the types defined in this document, could be used to cause execution of untrusted scripts through the inclusion of untrusted resource identifiers in otherwise trusted content. Security considerations of [RFC2397] apply. Implementations can fail to implement a specific security model or other means to prevent possibly dangerous operations. Such failure could possibly be exploited to gain unauthorized access to a system or sensitive information; such failure constitutes an unknown factor and is thus considered out of the scope of this document. 6. IANA Considerations The media type registrations herein are divided into two major categories: the sole media type "text/javascript" which is now in common usage, and all of the media types that are obsolete. For both categories, the media types are updated to reference [ECMA-262]. In addition, a new file extension of .mjs is added to the list of file extensions with the restriction that contents should be parsed using the Module goal. Finally, the [HTML] specification uses "text/javascript" as the default media type of ECMAScript when preparing script tags; therefore, "text/javascript" intended usage is to be moved from OBSOLETE to COMMON. These changes are to be reflected in the IANA Media Types registry in accordance with [RFC6838]. All registrations will point to this document as reference. The outdated note stating that the "text/ javascript" media type has been "OBSOLETED in favor of application/ javascript" is to be removed. The outdated note stating that the "text/ecmascript" media type has been "OBSOLETED in favor of application/ecmascript" is to be removed. IANA is requested to add the note "OBSOLETED in favor of text/javascript" to all registrations except "text/javascript". Miller, et al. Expires 15 April 2022 [Page 9] Internet-Draft ECMAScript Media Types Updates October 2021 6.1. Common JavaScript Media Types 6.1.1. text/javascript Type name: text Subtype name: javascript Required parameters: N/A Optional parameters: charset, see section 4.1 of [this document]. Encoding considerations: Binary Security considerations: See section 5 of [this document].. Interoperability considerations: It is expected that implementations will behave as if this registration applies to later editions of [ECMA-262], and its published specification references may be updated accordingly from time to time. See also various sections of [this document]. Published specification: [ECMA-262] Applications which use this media type: Script interpreters as discussed in [this document]. Additional information: Magic number(s): n/a File extension(s): .js, .mjs Macintosh File Type Code(s): TEXT Person & email address to contact for further information: See Author's Address section of [this document] and [RFC4329]. Intended usage: COMMON Restrictions on usage: The .mjs file extension signals that the file represents a JavaScript module. Execution environments that rely on file extensions to determine how to process inputs parse .mjs files using the Module grammar of [ECMA-262]. Author: See Author's Address section of [this document]. Change controller: IESG Miller, et al. Expires 15 April 2022 [Page 10] Internet-Draft ECMAScript Media Types Updates October 2021 6.2. Historic Javascript Media Types The following media types are added or updated for historical purposes. All herein have an intended usage of OBSOLETE, and are not expected to be in use with modern implementations. 6.2.1. application/ecmascript Type name: application Subtype name: ecmascript Required parameters: N/A Optional parameters: charset, see section 4.1 of [this document]. Encoding considerations: Binary Security considerations: See section 5 of [this document].. Interoperability considerations: It is expected that implementations will behave as if this registration applies to later editions of [ECMA-262], and its published specification references may be updated accordingly from time to time. See also various sections of [this document]. Published specification: [ECMA-262] Applications which use this media type: Script interpreters as discussed in [this document]. Additional information: Magic number(s): n/a File extension(s): .es, .mjs Macintosh File Type Code(s): TEXT Person & email address to contact for further information: See Author's Address section of [this document] and [RFC4329]. Intended usage: OBSOLETE Restrictions on usage: This media type is obsolete; current implementations should use text/javascript as the only JavaScript/ ECMAScript media type. The .mjs file extension signals that the file represents a JavaScript module. Execution environments that rely on file extensions to determine how to process inputs parse .mjs files using the Module grammar of [ECMA-262]. Miller, et al. Expires 15 April 2022 [Page 11] Internet-Draft ECMAScript Media Types Updates October 2021 Author: See Author's Address section of [this document]. Change controller: IESG 6.2.2. application/javascript Type name: application Subtype name: javascript Required parameters: N/A Optional parameters: charset, see section 4.1 of [this document]. Encoding considerations: Binary Security considerations: See section 5 of [this document].. Interoperability considerations: It is expected that implementations will behave as if this registration applies to later editions of [ECMA-262], and its published specification references may be updated accordingly from time to time. See also section 4.1 of [this document] regarding the charset parameter. Published specification: [ECMA-262] Applications which use this media type: Script interpreters as discussed in [this document]. Additional information: Magic number(s): n/a File extension(s): .js, .mjs Macintosh File Type Code(s): TEXT Person & email address to contact for further information: See Author's Address section of [this document] and [RFC4329]. Intended usage: OBSOLETE Restrictions on usage: This media type is obsolete; current implementations should use text/javascript as the only JavaScript/ ECMAScript media type. The .mjs file extension signals that the file represents a JavaScript module. Execution environments that rely on file extensions to determine how to process inputs parse .mjs files using the Module grammar of [ECMA-262]. Author: See Author's Address section of [this document]. Miller, et al. Expires 15 April 2022 [Page 12] Internet-Draft ECMAScript Media Types Updates October 2021 Change controller: IESG . 6.2.3. application/x-ecmascript Type name: application Subtype name: x-ecmascript Required parameters: N/A Optional parameters: : charset, see section 4.1 of [this document]. Encoding considerations: Binary Security considerations: See section 5 of [this document].. Interoperability considerations: It is expected that implementations will behave as if this registration applies to later editions of [ECMA-262], and its published specification references may be updated accordingly from time to time. See also various sections of [this document]. Published specification: [ECMA-262] Applications which use this media type: Script interpreters as discussed in [this document]. Additional information: Magic number(s): n/a File extension(s): .es, .mjs Macintosh File Type Code(s): TEXT Person & email address to contact for further information: See Author's Address section of [this document]. Intended usage: OBSOLETE Restrictions on usage: This media type is obsolete; current implementations should use text/javascript as the only JavaScript/ ECMAScript media type. The .mjs file extension signals that the file represents a JavaScript module. Execution environments that rely on file extensions to determine how to process inputs parse .mjs files using the Module grammar of [ECMA-262]. Author: See Author's Address section of [this document]. Change controller: IESG Miller, et al. Expires 15 April 2022 [Page 13] Internet-Draft ECMAScript Media Types Updates October 2021 6.2.4. application/x-javascript Type name: application Subtype name: x-javascript Required parameters: N/A Optional parameters: : charset, see section 4.1 of [this document]. Encoding considerations: Binary Security considerations: See section 5 of [this document].. Interoperability considerations: It is expected that implementations will behave as if this registration applies to later editions of [ECMA-262], and its published specification references may be updated accordingly from time to time. See also various sections of [this document]. Published specification: [ECMA-262] Applications which use this media type: Script interpreters as discussed in [this document]. Additional information: Magic number(s): n/a File extension(s): .js, .mjs Macintosh File Type Code(s): TEXT Person & email address to contact for further information: See Author's Address section of [this document]. Intended usage: OBSOLETE Restrictions on usage: This media type is obsolete; current implementations should use text/javascript as the only JavaScript/ ECMAScript media type. The .mjs file extension signals that the file represents a JavaScript module. Execution environments that rely on file extensions to determine how to process inputs parse .mjs files using the Module grammar of [ECMA-262]. Author: See Author's Address section of [this document]. Change controller: IESG Miller, et al. Expires 15 April 2022 [Page 14] Internet-Draft ECMAScript Media Types Updates October 2021 6.2.5. text/ecmascript Type name: text Subtype name: ecmascript Required parameters: N/A Optional parameters: : charset, see section 4.1 of [this document]. Encoding considerations: Binary Security considerations: See section 5 of [this document].. Interoperability considerations: It is expected that implementations will behave as if this registration applies to later editions of [ECMA-262], and its published specification references may be updated accordingly from time to time. See also various sections of [this document]. Published specification: [ECMA-262] Applications which use this media type: Script interpreters as discussed in [this document]. Additional information: Magic number(s): n/a File extension(s): .es, .mjs Macintosh File Type Code(s): TEXT Person & email address to contact for further information: See Author's Address section of [this document] and [RFC4329]. Intended usage: OBSOLETE Restrictions on usage: This media type is obsolete; current implementations should use text/javascript as the only JavaScript/ ECMAScript media type. The .mjs file extension signals that the file represents a JavaScript module. Execution environments that rely on file extensions to determine how to process inputs parse .mjs files using the Module grammar of [ECMA-262]. Author: See Author's Address section of [this document]. Change controller: IESG Miller, et al. Expires 15 April 2022 [Page 15] Internet-Draft ECMAScript Media Types Updates October 2021 6.2.6. text/javascript1.0 Type name: text Subtype name: javascript1.0 Required parameters: N/A Optional parameters: : charset, see section 4.1 of [this document]. Encoding considerations: Binary Security considerations: See section 5 of [this document].. Interoperability considerations: It is expected that implementations will behave as if this registration applies to later editions of [ECMA-262], and its published specification references may be updated accordingly from time to time. See also various sections of [this document]. Published specification: [ECMA-262] Applications which use this media type: Script interpreters as discussed in [this document]. Additional information: Magic number(s): n/a File extension(s): .js, .mjs Macintosh File Type Code(s): TEXT Person & email address to contact for further information: See Author's Address section of [this document]. Intended usage: OBSOLETE Restrictions on usage: This media type is obsolete; current implementations should use text/javascript as the only JavaScript/ ECMAScript media type. The .mjs file extension signals that the file represents a JavaScript module. Execution environments that rely on file extensions to determine how to process inputs parse .mjs files using the Module grammar of [ECMA-262]. Author: See Author's Address section of [this document]. Change controller: IESG Miller, et al. Expires 15 April 2022 [Page 16] Internet-Draft ECMAScript Media Types Updates October 2021 6.2.7. text/javascript1.1 Type name: text Subtype name: javascript1.1 Required parameters: N/A Optional parameters: : charset, see section 4.1 of [this document]. Encoding considerations: Binary Security considerations: See section 5 of [this document].. Interoperability considerations: It is expected that implementations will behave as if this registration applies to later editions of [ECMA-262], and its published specification references may be updated accordingly from time to time. See also various sections of [this document]. Published specification: [ECMA-262] Applications which use this media type: Script interpreters as discussed in [this document]. Additional information: Magic number(s): n/a File extension(s): .js, .mjs Macintosh File Type Code(s): TEXT Person & email address to contact for further information: See Author's Address section of [this document]. Intended usage: OBSOLETE Restrictions on usage: This media type is obsolete; current implementations should use text/javascript as the only JavaScript/ ECMAScript media type. The .mjs file extension signals that the file represents a JavaScript module. Execution environments that rely on file extensions to determine how to process inputs parse .mjs files using the Module grammar of [ECMA-262]. Author: See Author's Address section of [this document]. Change controller: IESG Miller, et al. Expires 15 April 2022 [Page 17] Internet-Draft ECMAScript Media Types Updates October 2021 6.2.8. text/javascript1.2 Type name: text Subtype name: javascript1.2 Required parameters: N/A Optional parameters: : charset, see section 4.1 of [this document]. Encoding considerations: Binary Security considerations: See section 5 of [this document].. Interoperability considerations: It is expected that implementations will behave as if this registration applies to later editions of [ECMA-262], and its published specification references may be updated accordingly from time to time. See also various sections of [this document]. Published specification: [ECMA-262] Applications which use this media type: Script interpreters as discussed in [this document]. Additional information: Magic number(s): n/a File extension(s): .js, .mjs Macintosh File Type Code(s): TEXT Person & email address to contact for further information: See Author's Address section of [this document]. Intended usage: OBSOLETE Restrictions on usage: This media type is obsolete; current implementations should use text/javascript as the only JavaScript/ ECMAScript media type. The .mjs file extension signals that the file represents a JavaScript module. Execution environments that rely on file extensions to determine how to process inputs parse .mjs files using the Module grammar of [ECMA-262]. Author: See Author's Address section of [this document]. Change controller: IESG Miller, et al. Expires 15 April 2022 [Page 18] Internet-Draft ECMAScript Media Types Updates October 2021 6.2.9. text/javascript1.3 Type name: text Subtype name: javascript1.3 Required parameters: N/A Optional parameters: : charset, see section 4.1 of [this document]. Encoding considerations: Binary Security considerations: See section 5 of [this document].. Interoperability considerations: It is expected that implementations will behave as if this registration applies to later editions of [ECMA-262], and its published specification references may be updated accordingly from time to time. See also various sections of [this document]. Published specification: [ECMA-262] Applications which use this media type: Script interpreters as discussed in [this document]. Additional information: Magic number(s): n/a File extension(s): .js, .mjs Macintosh File Type Code(s): TEXT Person & email address to contact for further information: See Author's Address section of [this document]. Intended usage: OBSOLETE Restrictions on usage: This media type is obsolete; current implementations should use text/javascript as the only JavaScript/ ECMAScript media type. The .mjs file extension signals that the file represents a JavaScript module. Execution environments that rely on file extensions to determine how to process inputs parse .mjs files using the Module grammar of [ECMA-262]. Author: See Author's Address section of [this document]. Change controller: IESG Miller, et al. Expires 15 April 2022 [Page 19] Internet-Draft ECMAScript Media Types Updates October 2021 6.2.10. text/javascript1.4 Type name: text Subtype name: javascript1.4 Required parameters: N/A Optional parameters: : charset, see section 4.1 of [this document]. Encoding considerations: Binary Security considerations: See section 5 of [this document].. Interoperability considerations: It is expected that implementations will behave as if this registration applies to later editions of [ECMA-262], and its published specification references may be updated accordingly from time to time. See also various sections of [this document]. Published specification: [ECMA-262] Applications which use this media type: Script interpreters as discussed in [this document]. Additional information: Magic number(s): n/a File extension(s): .js, .mjs Macintosh File Type Code(s): TEXT Person & email address to contact for further information: See Author's Address section of [this document]. Intended usage: OBSOLETE Restrictions on usage: This media type is obsolete; current implementations should use text/javascript as the only JavaScript/ ECMAScript media type. The .mjs file extension signals that the file represents a JavaScript module. Execution environments that rely on file extensions to determine how to process inputs parse .mjs files using the Module grammar of [ECMA-262]. Author: See Author's Address section of [this document]. Change controller: IESG Miller, et al. Expires 15 April 2022 [Page 20] Internet-Draft ECMAScript Media Types Updates October 2021 6.2.11. text/javascript1.5 Type name: text Subtype name: javascript1.5 Required parameters: N/A Optional parameters: : charset, see section 4.1 of [this document]. Encoding considerations: Binary Security considerations: See section 5 of [this document].. Interoperability considerations: It is expected that implementations will behave as if this registration applies to later editions of [ECMA-262], and its published specification references may be updated accordingly from time to time. See also various sections of [this document]. Published specification: [ECMA-262] Applications which use this media type: Script interpreters as discussed in [this document]. Additional information: Magic number(s): n/a File extension(s): .js, .mjs Macintosh File Type Code(s): TEXT Person & email address to contact for further information: See Author's Address section of [this document]. Intended usage: OBSOLETE Restrictions on usage: This media type is obsolete; current implementations should use text/javascript as the only JavaScript/ ECMAScript media type. The .mjs file extension signals that the file represents a JavaScript module. Execution environments that rely on file extensions to determine how to process inputs parse .mjs files using the Module grammar of [ECMA-262]. Author: See Author's Address section of [this document]. Change controller: IESG Miller, et al. Expires 15 April 2022 [Page 21] Internet-Draft ECMAScript Media Types Updates October 2021 6.2.12. text/jscript Type name: text Subtype name: jscript Required parameters: N/A Optional parameters: : charset, see section 4.1 of [this document]. Encoding considerations: Binary Security considerations: See section 5 of [this document].. Interoperability considerations: It is expected that implementations will behave as if this registration applies to later editions of [ECMA-262], and its published specification references may be updated accordingly from time to time. See also various sections of [this document]. Published specification: [ECMA-262] Applications which use this media type: Script interpreters as discussed in [this document]. Additional information: Magic number(s): n/a File extension(s): .js, .mjs Macintosh File Type Code(s): TEXT Person & email address to contact for further information: See Author's Address section of [this document]. Intended usage: OBSOLETE Restrictions on usage: This media type is obsolete; current implementations should use text/javascript as the only JavaScript/ ECMAScript media type. The .mjs file extension signals that the file represents a JavaScript module. Execution environments that rely on file extensions to determine how to process inputs parse .mjs files using the Module grammar of [ECMA-262]. Author: See Author's Address section of [this document]. Change controller: IESG Miller, et al. Expires 15 April 2022 [Page 22] Internet-Draft ECMAScript Media Types Updates October 2021 6.2.13. text/livescript Type name: text Subtype name: livescript Required parameters: N/A Optional parameters: : charset, see section 4.1 of [this document]. Encoding considerations: Binary Security considerations: See section 5 of [this document].. Interoperability considerations: See various sections of [this document]. Published specification: [ECMA-262] Applications which use this media type: Script interpreters as discussed in [this document]. Additional information: Magic number(s): n/a File extension(s): .js, .mjs Macintosh File Type Code(s): TEXT Person & email address to contact for further information: See Author's Address section of [this document]. Intended usage: OBSOLETE Restrictions on usage: This media type is obsolete; current implementations should use text/javascript as the only JavaScript/ ECMAScript media type. The .mjs file extension signals that the file represents a JavaScript module. Execution environments that rely on file extensions to determine how to process inputs parse .mjs files using the Module grammar of [ECMA-262]. Author: See Author's Address section of [this document]. Change controller: IESG 6.2.14. text/x-ecmascript Type name: text Miller, et al. Expires 15 April 2022 [Page 23] Internet-Draft ECMAScript Media Types Updates October 2021 Subtype name: x-ecmascript Required parameters: N/A Optional parameters: : charset, see section 4.1 of [this document]. Encoding considerations: Binary Security considerations: See section 5 of [this document].. Interoperability considerations: It is expected that implementations will behave as if this registration applies to later editions of [ECMA-262], and its published specification references may be updated accordingly from time to time. See also various sections of [this document]. Published specification: [ECMA-262] Applications which use this media type: Script interpreters as discussed in [this document]. Additional information: Magic number(s): n/a File extension(s): .es, .mjs Macintosh File Type Code(s): TEXT Person & email address to contact for further information: See Author's Address section of [this document]. Intended usage: OBSOLETE Restrictions on usage: This media type is obsolete; current implementations should use text/javascript as the only JavaScript/ ECMAScript media type. The .mjs file extension signals that the file represents a JavaScript module. Execution environments that rely on file extensions to determine how to process inputs parse .mjs files using the Module grammar of [ECMA-262]. Author: See Author's Address section of [this document]. Change controller: IESG 6.2.15. text/x-javascript Type name: text Subtype name: x-javascript Miller, et al. Expires 15 April 2022 [Page 24] Internet-Draft ECMAScript Media Types Updates October 2021 Required parameters: N/A Optional parameters: : charset, see section 4.1 of [this document]. Encoding considerations: Binary Security considerations: See section 5 of [this document].. Interoperability considerations: It is expected that implementations will behave as if this registration applies to later editions of [ECMA-262], and its published specification references may be updated accordingly from time to time. See also various sections of [this document]. Published specification: [ECMA-262] Applications which use this media type: Script interpreters as discussed in [this document]. Additional information: Magic number(s): n/a File extension(s): .js, .mjs Macintosh File Type Code(s): TEXT Person & email address to contact for further information: See Author's Address section of [this document]. Intended usage: OBSOLETE Restrictions on usage: This media type is obsolete; current implementations should use text/javascript as the only JavaScript/ ECMAScript media type. The .mjs file extension signals that the file represents a JavaScript module. Execution environments that rely on file extensions to determine how to process inputs parse .mjs files using the Module grammar of [ECMA-262]. Author: See Author's Address section of [this document]. Change controller: IESG 7. References 7.1. Normative References [CHARSETS] IANA, "Assigned character sets", n.d., . Miller, et al. Expires 15 April 2022 [Page 25] Internet-Draft ECMAScript Media Types Updates October 2021 [ECMA-262] Ecma International, "ECMAScript 2021 language specification, ECMA-262 12th Edition, June 2021", June 2021, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2397] Masinter, L., "The "data" URL scheme", RFC 2397, DOI 10.17487/RFC2397, August 1998, . [RFC2978] Freed, N. and J. Postel, "IANA Charset Registration Procedures", BCP 19, RFC 2978, DOI 10.17487/RFC2978, October 2000, . [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC Text on Security Considerations", BCP 72, RFC 3552, DOI 10.17487/RFC3552, July 2003, . [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 2003, . [RFC4329] Hoehrmann, B., "Scripting Media Types", RFC 4329, DOI 10.17487/RFC4329, April 2006, . [RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in Internationalization in the IETF", BCP 166, RFC 6365, DOI 10.17487/RFC6365, September 2011, . [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type Specifications and Registration Procedures", BCP 13, RFC 6838, DOI 10.17487/RFC6838, January 2013, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 7.2. Informative References Miller, et al. Expires 15 April 2022 [Page 26] Internet-Draft ECMAScript Media Types Updates October 2021 [HTML] WHATWG, "HTML Living Standard", August 2017, . [RFC3236] Baker, M. and P. Stark, "The 'application/xhtml+xml' Media Type", RFC 3236, DOI 10.17487/RFC3236, January 2002, . [RFC3875] Robinson, D. and K. Coar, "The Common Gateway Interface (CGI) Version 1.1", RFC 3875, DOI 10.17487/RFC3875, October 2004, . [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, . [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987, January 2005, . [SPECTRE] Kocher, P., Fogh, A., Gerkin, D., Gruss, D., Haas, W., Hamburg, M., Lipp, M., Mangard, S., Prescher, T., Schwarz, M., and Y. Yarom, "Spectre Attacks: Exploiting Speculative Execution", January 2018, . [TC39-MIME-ISSUE] TC39, "Add `application/javascript+module` mime to remove ambiguity", August 2017, . Appendix A. Acknowledgements This work builds upon its antecedent document, authored by Bjoern Hoehrmann. The authors would like to thank Adam Roach, Anne van Kesteren, Allen Wirfs-Brock, Alexey Melnikov, James Snell, Mark Nottingham, Murray Kucherawy, and Suresh Krishnan for their guidance and feedback throughout this process. Appendix B. Changes from RFC 4329 * Added a section discussing ECMAScript modules and the impact on processing. * Updated the Security Considerations to discuss concerns associated with ECMAScript modules and SharedArrayBuffers. Miller, et al. Expires 15 April 2022 [Page 27] Internet-Draft ECMAScript Media Types Updates October 2021 * Updated the character encoding scheme detection to remove normative guidance on its use, to better reflect operational reality. * Changed the intended usage of the media type text/javascript from obsolete to common. * Changed the intended usage for all other script media types to obsolete. * Updated various references where the original has been obsoleted. * Updated references to ECMA-262 to match the version at time of publication. Authors' Addresses Matthew A. Miller Email: linuxwolf+ietf@outer-planes.net Myles Borins GitHub Email: mylesborins@github.com Mathias Bynens Google Email: mths@google.com Bradley Farias Email: bradley.meck@gmail.com Miller, et al. 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