ECMAScript Media Types Updates
draft-ietf-dispatch-javascript-mjs-09
DISPATCH M. Miller
Internet-Draft
Obsoletes: 4329 (if approved) M. Borins
Intended status: Informational GitHub
Expires: January 1, 2022 M. Bynens
Google
B. Farias
June 30, 2021
ECMAScript Media Types Updates
draft-ietf-dispatch-javascript-mjs-09
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 January 1, 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
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carefully, as they describe your rights 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 . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
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 . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6.1. Common Javascript Media Types . . . . . . . . . . . . . . 9
6.1.1. text/javascript . . . . . . . . . . . . . . . . . . . 9
6.2. Historic Javascript Media Types . . . . . . . . . . . . . 10
6.2.1. application/ecmascript . . . . . . . . . . . . . . . 10
6.2.2. application/javascript . . . . . . . . . . . . . . . 11
6.2.3. application/x-ecmascript . . . . . . . . . . . . . . 12
6.2.4. application/x-javascript . . . . . . . . . . . . . . 13
6.2.5. text/ecmascript . . . . . . . . . . . . . . . . . . . 14
6.2.6. text/javascript1.0 . . . . . . . . . . . . . . . . . 15
6.2.7. text/javascript1.1 . . . . . . . . . . . . . . . . . 16
6.2.8. text/javascript1.2 . . . . . . . . . . . . . . . . . 17
6.2.9. text/javascript1.3 . . . . . . . . . . . . . . . . . 18
6.2.10. text/javascript1.4 . . . . . . . . . . . . . . . . . 19
6.2.11. text/javascript1.5 . . . . . . . . . . . . . . . . . 20
6.2.12. text/jscript . . . . . . . . . . . . . . . . . . . . 21
6.2.13. text/livescript . . . . . . . . . . . . . . . . . . . 22
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 . . . . . . . . . . . . . . . . . . 26
Appendix B. Changes from RFC 4329 . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
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
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languages. This document updates the descriptions and registrations
for these media types to reflect existing usage on the Internet.
This document replaces the media types registrations in [RFC4329],
obsoleting that document.
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. Differences in ECMAScript versions have been better
dealt with in the processors.
The types defined in this document are applicable to scripts written
in [ECMA-262]. This document does not address scripts written in
other languages. In particular, future editions of [ECMA-262] and
extensions to [ECMA-262] are not directly addressed.
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.
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.
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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 in the Module or Script grammar goals based
upon content alone. Therefore, scripting environments MUST use out
of band information in order to determine what goal a Source Text
should be treated as. To this end some scripting environments have
chosen to adopt the new 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 [RFC6265] 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 and source
text are 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.
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;
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other character encoding schemes MAY be supported, but are
discouraged.
4.1. Charset Parameter
The charset parameter provides a means to specify the character
encoding scheme of binary source text. Its value MUST match the
mime-charset production defined in [RFC2978], section 2.3, and SHOULD
be a registered charset [CHARSETS]. An illegal value is a value that
does not match that production.
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 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:
+------------------+----------+
| 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 with a legal and understood value is
specified, the value determines the character encoding scheme.
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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 legal according to that scheme. Implementations can
substitute those illegal sequences with the replacement character
U+FFFD (properly encoded for the scheme), or stop processing
altogether.
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
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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
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.
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.
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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.
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
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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 ECMAScript media types are to be updated to
point to a non-vendor specific standard undated specification of
ECMAScript. In addition, a new file extension of .mjs is to be added
to the list of file extensions with the restriction that it must
correspond to the Module grammar of [ECMA-262]. 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.
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: See various sections of [this
document].
Published specification: [this document]
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
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Macintosh File Type Code(s): TEXT
Person & email address to contact for further information: See
Author's Address section of [this document].
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 <iesg@ietf.org>
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: See various sections of [this
document].
Published specification: [this document]
Applications which use this media type: Script interpreters as
discussed in [this document].
Additional information:
Magic number(s): n/a
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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 <iesg@ietf.org>
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: charset, see section 4.1 of [this
document].
Published specification: [this document]
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
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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 <iesg@ietf.org>.
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: See various sections of [this
document].
Published specification: [this document]
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
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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 <iesg@ietf.org>
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: See various sections of [this
document].
Published specification: [this document]
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].
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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 <iesg@ietf.org>
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: See various sections of [this
document].
Published specification: [this document]
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
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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 <iesg@ietf.org>
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: See various sections of [this
document].
Published specification: [this document]
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/
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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 <iesg@ietf.org>
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: See various sections of [this
document].
Published specification: [this document]
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
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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 <iesg@ietf.org>
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: See various sections of [this
document].
Published specification: [this document]
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].
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Author: See Author's Address section of [this document].
Change controller: IESG <iesg@ietf.org>
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: See various sections of [this
document].
Published specification: [this document]
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].
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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: See various sections of [this
document].
Published specification: [this document]
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 <iesg@ietf.org>
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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: See various sections of [this
document].
Published specification: [this document]
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 <iesg@ietf.org>
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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: See various sections of [this
document].
Published specification: [this document]
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: 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 <iesg@ietf.org>
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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: [this document]
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: 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 <iesg@ietf.org>
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6.2.14. text/x-ecmascript
Type name: text
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: See various sections of [this
document].
Published specification: [this document]
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: 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 <iesg@ietf.org>
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6.2.15. text/x-javascript
Type name: text
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: See various sections of [this
document].
Published specification: [this document]
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: 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 <iesg@ietf.org>
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7. References
7.1. Normative References
[CHARSETS]
IANA, "Assigned character sets", n.d.,
<https://www.iana.org/assignments/character-sets>.
[ECMA-262]
Ecma International, "Standard ECMA-262: ECMAScript
Language Specification", June 2019, <https://ecma-
international.org/publications/standards/Ecma-262.htm>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2397] Masinter, L., "The "data" URL scheme", RFC 2397,
DOI 10.17487/RFC2397, August 1998,
<https://www.rfc-editor.org/info/rfc2397>.
[RFC2978] Freed, N. and J. Postel, "IANA Charset Registration
Procedures", BCP 19, RFC 2978, DOI 10.17487/RFC2978,
October 2000, <https://www.rfc-editor.org/info/rfc2978>.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003,
<https://www.rfc-editor.org/info/rfc3552>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <https://www.rfc-editor.org/info/rfc3629>.
[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,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987,
January 2005, <https://www.rfc-editor.org/info/rfc3987>.
[RFC4329] Hoehrmann, B., "Scripting Media Types", RFC 4329,
DOI 10.17487/RFC4329, April 2006,
<https://www.rfc-editor.org/info/rfc4329>.
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[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
DOI 10.17487/RFC6265, April 2011,
<https://www.rfc-editor.org/info/rfc6265>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
7.2. Informative References
[HTML] WHATWG, "HTML Living Standard", August 2017,
<https://html.spec.whatwg.org/multipage/
scripting.html#prepare-a-script>.
[RFC3236] Baker, M. and P. Stark, "The 'application/xhtml+xml' Media
Type", RFC 3236, DOI 10.17487/RFC3236, January 2002,
<https://www.rfc-editor.org/info/rfc3236>.
[RFC3875] Robinson, D. and K. Coar, "The Common Gateway Interface
(CGI) Version 1.1", RFC 3875, DOI 10.17487/RFC3875,
October 2004, <https://www.rfc-editor.org/info/rfc3875>.
[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,
<https://arxiv.org/abs/1801.01203>.
[TC39-MIME-ISSUE]
TC39, "Add `application/javascript+module` mime to remove
ambiguity", August 2017, <https://web.archive.org/web/2017
0814193912/https://github.com/tc39/ecma262/issues/322>.
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
o Added a section discussing ECMAscript modules and the impact on
processing.
o Updated the Security Considerations to discuss concerns associated
with ECMAscript modules and SharedArrayBuffers.
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o Updated the character encoding scheme detection to remove
normative guidance on its use, to better reflect operational
reality.
o Changed the intended usage of the media type text/javascript from
obsolete to common.
o Changed the intended usage for all other script media types to
obsolete.
o Updated various references where the original has been osboleted
o 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
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