WebAssembly/binaryen

Optimizer and compiler/toolchain library for WebAssembly

Stars: 8.6k
Forks: 885
Open beginner issues: 2
Indexed issues: 337
Avg merge: 2d 2h
Merged PRs (30d): 86

Dominant language: WebAssembly
License: Apache-2.0
Last GitHub push: Sep 19, 2026
Latest indexed: Sep 20, 2026
Contributing guide: Contributing guide
Code of conduct: Code of conduct
Beginner labels: help wanted

Beginner friendly Everything

Open All

Remove unnecessary null pointer checks Open

Difficulty 1/5 Under an hour Newbie friendliness 88/100

WebAssembly/binaryen#9135 · 1 comment · Opened Sep 22, 2026
Exact Type Precision vs Optimization Cost Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

WebAssembly/binaryen#9133 · Opened Sep 22, 2026
Complete the ChildTyper migration of validator child-type checks Open

Difficulty 4/5 3-5 days Newbie friendliness 52/100

WebAssembly/binaryen#9123 · Opened Sep 20, 2026
ChildTyper constraints drop sharedness, blocking validator migration Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

WebAssembly/binaryen#9122 · Opened Sep 20, 2026
Incomplete analysis for the states of global integer variables that does not eliminate excessive equality checks Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

WebAssembly/binaryen#9086 · 2 comments · Opened Sep 9, 2026
More precise livenes analysis for locals under Asyncify Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

WebAssembly/binaryen#9038 · 5 comments · Opened Aug 24, 2026
Most lit/help tests fail with new python-filecheck Open

Difficulty 2/5 Half a day Newbie friendliness 76/100

WebAssembly/binaryen#9018 · 3 comments · Opened Aug 19, 2026
ctor-eval/flatten_overflow.wast lit test fails on x86 32-bit Open

Difficulty 3/5 1-2 days Newbie friendliness 52/100

WebAssembly/binaryen#9006 · 2 comments · Opened Aug 15, 2026
wasm2c from binaryen conflicts with wasm2c from wabt Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

WebAssembly/binaryen#9002 · 4 comments · Opened Aug 13, 2026
Parse bug with extra non-nullable br_on_cast values Open

Difficulty 3/5 1-2 days Newbie friendliness 54/100

WebAssembly/binaryen#8949 · Opened Jul 29, 2026
Fuzzer generates invalid code for table initializers Open

Difficulty 3/5 1-2 days Newbie friendliness 68/100

WebAssembly/binaryen#8911 · 1 comment · Opened Jul 15, 2026
Investigate why `wasm-merge` + `wasm-opt` output is larger than the corresponding monolithic module processed with `wasm-opt` Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

WebAssembly/binaryen#8910 · 1 comment · Opened Jul 15, 2026
wasm-opt [parse exception: popping from empty stack (at 0:543)] Open

Difficulty 3/5 1-2 days Newbie friendliness 55/100

WebAssembly/binaryen#8896 · 2 comments · Opened Jul 12, 2026
Recognize table initialization code in start function and be able to devirtualize based on it Open

Difficulty 5/5 Over a week Newbie friendliness 42/100

WebAssembly/binaryen#8869 · 4 comments · Opened Jun 26, 2026
Missing validation error Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

WebAssembly/binaryen#8785 · 1 comment · Opened May 28, 2026
[wasm2c] Migrate to binaryen's existing hasher Open

Difficulty 3/5 1-2 days Newbie friendliness 58/100

WebAssembly/binaryen#8775 · Opened May 26, 2026
Assumptions for public types under --closed-world Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

WebAssembly/binaryen#8754 · 11 comments · Opened May 21, 2026
Asyncify produces invalid IR for inner passes Open

Difficulty 4/5 3-5 days Newbie friendliness 52/100

WebAssembly/binaryen#8753 · Opened May 21, 2026
support.run_command ignores --no-fail-fast Open

Difficulty 3/5 1-2 days Newbie friendliness 55/100

WebAssembly/binaryen#8735 · Opened May 20, 2026
Slow reduction using delta debugging Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

WebAssembly/binaryen#8712 · 18 comments · Opened May 15, 2026
Validator incorrectly rejects call_indirect to table of type `(ref null nofunc)` Open

WebAssembly/binaryen#8710 · 2 comments · 1 assignee · Opened May 15, 2026
TypeSSA could delete exactness Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

WebAssembly/binaryen#8694 · Opened May 12, 2026
Global store-to-load forwarding Open

Difficulty 4/5 3-5 days Newbie friendliness 46/100

WebAssembly/binaryen#8691 · 6 comments · Opened May 12, 2026
Optimization issue where allocation is not eliminated Open

WebAssembly/binaryen#8641 · 2 comments · 1 assignee · Opened Apr 22, 2026
heap-buffer-overflow in wasm::WATParser::Lexer::peek() at parser/lexer.h:137 (main branch @3ef8d19) Open

WebAssembly/binaryen#8632 · 1 assignee · Opened Apr 21, 2026
Branch hint fuzz bug with --code-pushing Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

WebAssembly/binaryen#8622 · 2 comments · Opened Apr 17, 2026
Improve effects analysis for indirect calls Open

Difficulty 4/5 3-5 days Newbie friendliness 25/100

WebAssembly/binaryen#8615 · Opened Apr 16, 2026
`Module.readBinary` use current spec as default feature set. Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

WebAssembly/binaryen#8560 · Opened Mar 31, 2026
MSVC builds seems to be full of warning, which makes debugging harder. Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

WebAssembly/binaryen#8546 · 1 comment · Opened Mar 30, 2026
Convert more test suits to use lit and/or parallel test runner Open

WebAssembly/binaryen#8520 · 6 comments · 1 assignee · Opened Mar 25, 2026
Requesting benchmarks to evaluate performance improvements. Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

WebAssembly/binaryen#8518 · 5 comments · Opened Mar 25, 2026
String escaping fuzz bug with wasm-metadce Open

WebAssembly/binaryen#8482 · 7 comments · 1 assignee · Opened Mar 18, 2026
Infinite wait in fuzzer Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

WebAssembly/binaryen#8429 · 4 comments · Opened Mar 7, 2026
~+700% regression in wasm-opt --nm performance from Emscripten 3.1.38 -> 4.0.19 Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

WebAssembly/binaryen#8406 · 9 comments · Opened Mar 2, 2026
Support `try_table` in Flatten Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

WebAssembly/binaryen#8372 · 9 comments · Opened Feb 24, 2026
`pass` test failures on 32-bit systems Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

WebAssembly/binaryen#8366 · 2 comments · Opened Feb 24, 2026
wasm-opt --flatten fails with exceptions or GC Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

WebAssembly/binaryen#8325 · 3 comments · Opened Feb 13, 2026
Waitqueue / waitqueue ref support in Binaryen Open

WebAssembly/binaryen#8315 · 1 comment · 1 assignee · Opened Feb 12, 2026
Wasm-opt not deduplicating repeated struct.gets on unchanged local Open

Difficulty 4/5 3-5 days Newbie friendliness 38/100

WebAssembly/binaryen#8312 · 3 comments · Opened Feb 12, 2026
Compiling to WGSL Open

Difficulty 5/5 Over a week Newbie friendliness 20/100

WebAssembly/binaryen#8266 · 2 reactions · Opened Feb 4, 2026
Improve interpreter spec test coverage Open

WebAssembly/binaryen#8261 · 21 comments · 1 assignee · Opened Feb 3, 2026
Avoid generating trampolines with --no-placeholders Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

WebAssembly/binaryen#8238 · 12 comments · 1 reaction · Opened Jan 27, 2026
Combining data segments Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

WebAssembly/binaryen#8198 · 2 comments · Opened Jan 13, 2026
Refactorings to imports in Binaryen Open

Difficulty 4/5 3-5 days Newbie friendliness 25/100

WebAssembly/binaryen#8180 · Opened Jan 6, 2026
ctor-eval crashes when a non-env imported memory is written to Open

WebAssembly/binaryen#8146 · 1 assignee · Opened Dec 18, 2025
ctor-eval crashes when the same name is imported twice Open

WebAssembly/binaryen#8138 · 2 comments · 1 assignee · Opened Dec 16, 2025
Discussion: Binaryen Wasm Component Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

WebAssembly/binaryen#8120 · 1 reaction · Opened Dec 13, 2025
Clean up FailToEvalExceptions and import stubbing in wasm-ctor.cpp Open

WebAssembly/binaryen#8117 · 1 assignee · Opened Dec 12, 2025
wasm-split fuzzing and reusing an existing Table Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

WebAssembly/binaryen#8106 · 5 comments · Opened Dec 8, 2025
Running `wasm-opt` with `-Os` leaves NOP / dead control flow behind Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

WebAssembly/binaryen#8077 · 11 comments · Opened Dec 1, 2025

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