Is there a published support lifecycle for Emscripten?

[John Dallman]

I haven't found one via web searching. 

Thanks,

John

[Sam Clegg]

I don't believe we have such I'm afraid.

Note that emscripten does rolling releases, always cut from the main branch.   We don't (or rather we have never done) any kind of branching or patching of existing releases.   So while we support our users no matter what version they are using, if you need a specific fix we always recommend upgrading the latest version.   You could, of course, backport patches yourself, but we never do this officially/upstream.

cheers,

sam

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[John Dallman]

Thanks for that. I've found the MIN_$RUNTIME_VERSION set of options; do those simply do a run-time version check so that a program can refuse to run on something it doesn't want to support, or do they affect wasm code generation? 

Thanks,

John  

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[Sam Clegg]

Ah, was your original question about the runtimes we support when generating code?  If so, then I misunderstood.

We don't have any official or hard-and-rules about how far back we go on browser/engine support, but we do go back a very long way.   When you opt into older browser support via MIN_XXX_VERSION (or using `LEGACY_VM_SUPPORT` which sets all the `MIN_XXX_VERSION` to their minimum values) that does indeed effec the generated code.  The idea is that the generated code will not contains new JS or Wasm features.  In some cases we run lowering passes on the Wasm file and for older JS engines we run babel on the output to transpile to ES5.

For the current set of minimum values see the documentation for each of the `MIN_XXX_VERSION` settings. e.g. https://emscripten.org/docs/tools_reference/settings_reference.html#min-chrome-version.   Here you can see we support chrome versions going back to Chrome 74 which is ~6 years old now.   You can also see all the minimum version here: https://github.com/emscripten-core/emscripten/blob/83df45fc083ef0560e5a5b0f4108195f1f07c859/tools/feature_matrix.py#L25-L30

See https://github.com/emscripten-core/emscripten/issues/20601 for a very old but ongoing discussion about creating some kind of official policy: https://github.com/emscripten-core/emscripten/issues/20601

cheers,

sam

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[John Dallman]

On Tue, Feb 10, 2026 at 6:46 PM 'Sam Clegg' via emscripten-discuss <emscripte...@googlegroups.com> wrote:

Ah, was your original question about the runtimes we support when generating code?  If so, then I misunderstood.

No, it wasn't. I simply found the MIN_X_VERSION options between asking the original question, and my reply to you.

 

We don't have any official or hard-and-rules about how far back we go on browser/engine support, but we do go back a very long way.   When you opt into older browser support via MIN_XXX_VERSION (or using `LEGACY_VM_SUPPORT` which sets all the `MIN_XXX_VERSION` to their minimum values) that does indeed effec the generated code.  The idea is that the generated code will not contains new JS or Wasm features.  In some cases we run lowering passes on the Wasm file and for older JS engines we run babel on the output to transpile to ES5.

I'm not intending to try to reach back a long way. I'm porting a big mathematical modelling library to WASM, and I am quite happy for it to require fairly recent browsers and run-times.  

I hadn't expected Emscripten to track all the features described in https://github.com/emscripten-core/emscripten/blob/83df45fc083ef0560e5a5b0f4108195f1f07c859/tools/feature_matrix.py, but I'm happy that it does. 

 

Thanks, 

John

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