WebAssembly Proposals Support

The following table summarizes Wasmtime's support for WebAssembly proposals as well as the command line flag and wasmtime::Config method you can use to enable or disable support for a proposal.

If a proposal is not listed, then it is not supported by Wasmtime.

Wasmtime will never enable a proposal by default unless it has reached phase 4 of the WebAssembly standardizations process and its implementation in Wasmtime has been thoroughly vetted.

WebAssembly ProposalSupported in Wasmtime?Command Line FlagConfig Method
Import and Export Mutable GlobalsYes.
Always enabled.
(none)(none)
Sign-Extension OperationsYes.
Always enabled.
(none)(none)
Non-Trapping Float-to-Int ConversionsYes.
Always enabled.
(none)(none)
Multi-ValueYes.
Enabled by default.
--enable-multi-valuewasm_multi_value
Bulk Memory OperationsYes.
Enabled by default.
--enable-bulk-memorywasm_bulk_memory
Reference TypesYes.
Enabled by default.
--enable-reference-typeswasm_reference_types
Fixed-Width SIMDIn progress.--enable-simdwasm_simd
Threads and AtomicsIn progress.--enable-threadswasm_threads
Multi-MemoryYes.--enable-multi-memorywasm_multi_memory