wasm-split

Add build ids to WebAssembly modules and split out debug data

Usage

sentry wasm-split <input>

Add build ids to WebAssembly modules and split out debug data

Arguments:

Argument	Description
<input>	Path to the wasm file

Options:

Option	Description
-o, --out <out>	Path to the output wasm file (default: modify input in place)
-d, --debug-out <debug-out>	Path to the output debug wasm file (default: debug data stays in the input)
--strip	Strip the file of debug info
--strip-names	Strip the file of symbol names (only with --strip)
-q, --quiet	Do not print the build id
--build-id <build-id>	Explicit build id to use, as a UUID
--external-dwarf-url <external-dwarf-url>	URL for browsers to fetch the separate DWARF debug symbol file

All commands support --json for machine-readable output and --fields to select specific JSON fields.

Examples

# Add a build id to a module, in place, and print it
sentry wasm-split app.wasm

# Capture the build id for a later upload
BUILD_ID=$(sentry wasm-split app.wasm)

# Split debug data into a companion and ship a stripped binary
sentry wasm-split app.wasm --debug-out app.debug.wasm --strip

# Also drop function names from the shipped binary
sentry wasm-split app.wasm -d app.debug.wasm --strip --strip-names

# Point browsers at a companion served from a CDN
sentry wasm-split app.wasm -o dist/app.wasm -d dist/app.debug.wasm --strip \
  --external-dwarf-url https://cdn.example.com/debug/app.debug.wasm

Important Notes

• This is a drop-in replacement for Symbolicator's wasm-split binary — same flags, same behaviour, same output.
• Only the build id is printed, as lowercase hex, so it can be captured in a shell variable. Pass --quiet to print nothing. --quiet cannot be combined with --json.
• A build id the module already carries is reused. Rewriting it would orphan debug files uploaded against the old one. --build-id applies only when the module has none.
• The debug companion is a complete copy of the module, captured before stripping. DWARF offsets are relative to the code section, so a companion missing it cannot be symbolicated. Expect it to be about the size of the input.
• --strip-names takes effect only alongside --strip.
• external_debug_info is written when --external-dwarf-url is given, or else from the basename of --debug-out. A bare filename resolves relative to the main wasm file, which is how Emscripten reads it.
• The file is left untouched when nothing changed — no new build id, no stripping, no external_debug_info — so reruns do not disturb build caches.