WebAssembly doesn't work on Firefox/Chrome due to missing MIME type

[DesWurstes@…]

WebAssembly's MIME type is application/wasm. If not set; Firefox, Chrome and Vivaldi won't be able to run the WASM.

Here's the Chrome error message:

util.js:1632 wasm streaming compile failed: TypeError: Failed to execute 'compile' on 'WebAssembly': Incorrect response MIME type. Expected 'application/wasm'.

Could you please add application/wasm wasm to nginx/conf/mime.types?

[Maxim Dounin]

Thanks for your suggestion. Note that if you want to add additional types or serve some files with specific custom types, you can do so using the types directive, see ​the documentation for examples.

Some related facts as found during a quick investigation, just for the record:

• The application/wasm MIME type is not something ​officially registered, though there is a ​provisional registration.
• The the WebAssembly specification isn't yet complete, though there is a ​public draft.
• The MIME type isn't present neither in ​Apache mime.types, nor in ​Python.
• It looks like it was (or going to be) added to IIS, see ​comments here.
• It was added to ​mime-db as used by Github Pages.

Note that we generally only add most popular types to the mime.types as shipped with nginx. It is not currently clear if application/wasm is one of such types, so leaving this open for now. If you are reading this and also want (or don't want) application/wasm to be added, please comment.

[dbrgn@…]

If you are reading this and also want (or don't want) application/wasm to be added, please comment.

I signed up here to say: Yes, I'd also like to see this type added! :)

The the WebAssembly specification isn't yet complete, though there is a ​public draft.

It's true that the spec isn't complete, but in the meantime the WebAssembly MVP (​https://webassembly.org/docs/mvp/) has shipped across all major browsers (at least Firefox, Chrome, Edge, Safari).

Oh, and it seems that the mime type has been ​added to cpython as well.

[ccouzens@…]

If you are reading this and also want (or don't want) application/wasm to be added, please comment.

Yes please, I would like to see this added. I have a ​patch, although it isn't exactly a complicated change.

The WebAssembly specification isn't yet complete, though there is a ​public draft.

It's now a "Proposed Recommendation", which is the final step to becoming a W3C recommendation (although they stress until it's a recommendation it's still a draft).

I think on balance it's reasonable for nginx to hold off until it's a W3C recommendation. I imagine it's easier for the nginx project to add it once it has become a recommendation, than to remove it should it fail.

[ccouzens@…]

The WebAssembly? specification isn't yet complete, though there is a ​public draft.

It's now a W3C recommendation. I think this happened today.
And it says that it should be served with the mime type application/wasm

​https://www.w3.org/TR/wasm-web-api-1/#streaming-modules