WebAssembly Specification — WebAssembly 3.0 (2026-06-13) Introduction Introduction Overview Structure Conventions Values Types Instructions Modules Validation Conventions Types Matching Instructions Modules Execution Conventions Runtime Structure Numerics Types Values Instructions Modules Binary Format Conventions Values Types Instructions Modules Text Format Conventions Lexical Format Values Types Instructions Modules Appendix Embedding Profiles Implementation Limitations Type Soundness Type System Properties Validation Algorithm Custom Sections and Annotations Change History Index of Types Index of Instructions Index of Semantic Rules Index of Types Index of Instructions Index of Semantic Rules Index