Reference

The Quickstart and Concepts pages cover the model. This section is for lookups — does the interpreter implement X, what’s the type of Y, what error fires on Z.

At a glance

Implemented:

• Every WebAssembly Core opcode (numeric, control flow, memory, tables, parametric, variables).
• Sign-extension proposal (i{32,64}.extend{8,16,32}_s).
• Non-trapping float-to-int (*.trunc_sat_f*_*).
• Bulk-memory (memory.{init,copy,fill}, data.drop, table.{init,copy,fill}, elem.drop).
• Reference types (funcref, externref, ref.{null,is_null,func}, table.{get,set,grow,size,fill}, typed select t*).
• Multi-memory (every memory opcode carries a memidx; modules may declare more than one memory).
• Full SIMD proposal — all ~236 ops under the 0xFD prefix (V128 value type plumbed end-to-end).
• Relaxed SIMD — all 20 sub-opcodes (0x100..0x113).
• Exception handling — both legacy (try / catch / throw / rethrow / delegate) and modern (try_table + throw_ref + exnref).
• Tail calls (return_call / return_call_indirect).
• Threads / atomics — 66 atomic sub-opcodes + shared memory + wait / notify / fence.
• Multi-value blocks + functions.
• Start section.
• Validation pass that runs before any code does.

Not implemented:

• Function references proposal (typed (ref null func) short-form reftype with wire byte 0x63).
• GC proposal (struct.*, array.*, ref.cast).
• Component model (out of scope — packaging proposal, not a wasm core feature).

See Opcodes for the by-byte detail.

• Opcodes — every WebAssembly opcode group, supported or planned.
• Errors — the WasmError ADT in one table.
• Spec compliance — running the W3C testsuite against the interpreter.