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WebAssembly proposals

Active proposals

Proposals follow this process document.

Phase 5 - The Feature is Standardized (WG)

These proposals have not yet been merged to the spec. Merged proposals are listed in Finished Proposals.

Proposal Champion

Phase 4 - Standardize the Feature (WG)

Proposal Champion
Tail call Andreas Rossberg
Extended Constant Expressions Sam Clegg
Typed Function References Andreas Rossberg
Garbage collection Andreas Rossberg
Multiple memories Andreas Rossberg
Threads Conrad Watt
Relaxed SIMD Marat Dukhan & Zhi An Ng

Phase 3 - Implementation Phase (CG + WG)

Proposal Champion
Custom Annotation Syntax in the Text Format Andreas Rossberg
Memory64 Sam Clegg
Exception handling Heejin Ahn & Ben Titzer
Web Content Security Policy Francis McCabe
Branch Hinting Yuri Iozzelli
JS Promise Integration Ross Tate and Francis McCabe
Type Reflection for WebAssembly JavaScript API Ilya Rezvov
ESM Integration Asumu Takikawa, Ms2ger & Guy Bedford

Phase 2 - Proposed Spec Text Available (CG + WG)

Proposal Champion
Relaxed dead code validation Conrad Watt and Ross Tate
Numeric Values in WAT Data Segments Ezzat Chamudi
Instrument and Tracing Technology Richard Winterton
Extended Name Section Ashley Nelson
JS String Builtins Ryan Hunt

Phase 1 - Feature Proposal (CG)

Proposal Champion
Type Imports Andreas Rossberg
Component Model Luke Wagner
WebAssembly C and C++ API Andreas Rossberg
Flexible Vectors Petr Penzin & Tal Garfinkel
Call Tags Ross Tate
Stack Switching Francis McCabe & Sam Lindley
Constant Time Sunjay Cauligi, Garrett Gu, John Renner, Hovav Shacham, Deian Stefan, Conrad Watt
JS Customization for GC Objects Asumu Takikawa
Memory control Deepti Gandluri & Ben Visness
Reference-Typed Strings Andy Wingo
Profiles Andreas Rossberg
Rounding Variants Kloud Koder
Shared-Everything Threads Andrew Brown, Conrad Watt, and Thomas Lively
Frozen Values Léo Andrès and Pierre Chambart
Compilation Hints Emanuel Ziegler
Custom Page Sizes Nick Fitzgerald
Half Precision Ilya Rezvov

Phase 0 - Pre-Proposal (CG)

Proposal Champion

Implementation status

Implementation status of most proposals in various wasm engines is available on

Contributing new proposals

Please see Contributing to WebAssembly for the most up-to-date information on contributing proposals to standard.