Platform Tags & Compatibility

Platform Tags & Compatibility#

The Emscripten/WebAssembly platform for Python is standardized by PEP 783.

Platform tag format#

Wheels built by pyodide-build use the platform tag:

pyemscripten_{year}_{patch}_wasm32

A complete wheel filename:

numpy-2.2.0-cp314-cp314-pyemscripten_2026_0_wasm32.whl
       │      │     │           │
       │      │     │           └── platform tag
       │      │     └── Python ABI tag
       │      └── Python version tag
       └── package version

Compatibility matrix#

Each platform version is tied to a specific Python version and Emscripten SDK version. Wheels built for one platform version are not compatible with another.

Platform tag	Python	Emscripten	Notes
`emscripten_3_1_32_wasm32`	3.11	3.1.32	Legacy tag name
`pyodide_2024_0_wasm32`	3.12	3.1.58	Legacy tag name
`pyodide_2025_0_wasm32`	3.13	4.0.9	Legacy tag name
`pyemscripten_2026_0_wasm32`	3.14	5.0.3	PEP 783 standardized name

Note

Older Pyodide versions used the tag pyodide_{year}_{patch}_wasm32 or emscripten_{version}_wasm32. The pyemscripten_* tag is the standardized form going forward per PEP 783.

ABI compatibility rules#

Wheels are not cross-version compatible — a wheel built for pyemscripten_2025_0_wasm32 will not work with pyemscripten_2024_0_wasm32 or pyemscripten_2026_0_wasm32.
Pure Python wheels (py3-none-any) work on all versions.
The ABI version determines which Emscripten SDK and CPython build are used. Mixing versions will cause load-time or runtime errors.

cibuildwheel identifiers#

When using cibuildwheel, the platform identifiers are:

cibuildwheel identifier
`cp312-pyodide_wasm32`
`cp313-pyodide_wasm32`
`cp314-pyodide_wasm32`

Checking your platform version#

pyodide config get pyodide_abi_version