Description

johnfraney

opened on Nov 3, 2025

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Feature or enhancement

Proposal:

.cjs is a JavaScript extension for CommonJS modules and is used pretty commonly (ha) by JS like Vite. It's also a format that NodeJS supports.

It could be good to add it to mimetypes since it is a widely-used extension.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-140942: Add MIME type for .cjs extension #140937

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1. johnfraney

   added

   type-featureA feature request or enhancementA feature request or enhancement

   on Nov 3, 2025
2. StanFromIreland

   added

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   on Nov 3, 2025
3. StanFromIreland commented on Nov 3, 2025

   

   StanFromIreland

   on Nov 3, 2025

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   I do not think this change is correct, it is not officially registered with IANA as required, .cjs is not listed as an alias of text/javascript:

   File extension(s): .js, .mjs
4. StanFromIreland

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   pendingThe issue will be closed if no feedback is providedThe issue will be closed if no feedback is provided

   on Nov 3, 2025
5. ZeroIntensity commented on Nov 3, 2025

   

   ZeroIntensity

   on Nov 3, 2025

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   I'm not sure that mimetypes is supposed to be 100% compliant with IANA. For example, we support the .jpe extension for JPEG files, despite that not being specified.

   There are also several supported extensions for application/octet-stream, and IANA doesn't specify any file extension for that. That suggests IANA's file extension specification isn't meant to be exhaustive.
6. StanFromIreland commented on Nov 3, 2025

   

   StanFromIreland

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   The two cases you mentioned exist in mimetypes since 1997 (ac8a9f3), only in 2006 was the comment requiring they be registered added.
7. StanFromIreland commented on Nov 3, 2025

   

   StanFromIreland

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   We can put it in common_types, which allows for non-IANA registered types. Per the documentation:

   The optional strict argument is a flag specifying whether the list of known MIME types is limited to only the official types registered with IANA.

   Reacted by Peter Bierma
8. StanFromIreland

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   pendingThe issue will be closed if no feedback is providedThe issue will be closed if no feedback is provided

   on Nov 3, 2025
9. picnixz commented on Nov 3, 2025

   

   picnixz

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   FTR, mimetypes is supposed to be IANA compliant, as per the comment:

   # Before adding new types, make sure they are either registered with IANA,
   # at https://www.iana.org/assignments/media-types/media-types.xhtml
   # or extensions, i.e. using the x- prefix
   

   The reason why .exe & co are mapped to octect-stream is likely for convenience (the IANA type for .exe is https://www.iana.org/assignments/media-types/application/vnd.microsoft.portable-executable) and using octect-stream instead to indicate binary data is probably the best practical choice.
10. johnfraney commented on Nov 4, 2025

    

    johnfraney

    on Nov 4, 2025

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    We can put it in common_types, which allows for non-IANA registered types. Per the documentation:

    Oh! Thank you, @StanFromIreland. I missed that comment. I'll put up a PR with that extension added to common_types instead
11. StanFromIreland commented on Nov 4, 2025

    

    StanFromIreland

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    The reason why .exe & co are mapped to octect-stream is likely for convenience (the IANA type for .exe is https://www.iana.org/assignments/media-types/application/vnd.microsoft.portable-executable)

    That seems like a bug, the addition of .exe (1997) predates the official registration (2015) of the application/vnd.microsoft.portable-executable mimetype.
12. hugovk

    closed this as completedin #140937on Nov 11, 2025
13. hugovk

    added a commit that references this issue on Nov 11, 2025

    gh-140942: Add MIME type for .cjs extension (#140937)

    d890aba
14. StanFromIreland

    added a commit that references this issue on Dec 6, 2025

    pythongh-140942: Add MIME type for .cjs extension (python#140937)

    1cf989e

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