go-exiftool: ExifTool in Go (zeroperl + wazero)

Go library that runs ExifTool in-process: embedded Perl via zeroperl (Perl compiled to WebAssembly), executed with wazero. You do not need a system exiftool binary or a separate Perl install.

Upstream ExifTool (Phil Harvey) and metadata: exiftool.org, exiftool/exiftool.

Why this shape

• Self-contained — Perl stdlib, ExifTool, and the interpreter ship inside the module (embed/).
• Same behavior everywhere — one WASM stack on Linux, macOS, Windows, etc.
• Trade-off — cold start is heavy (on the order of ~7–10 seconds to compile/instantiate WASM and init Perl). For many operations, use NewServer and Server.Command so ExifTool stays open (-stay_open) and work is amortized.

Requirements

• Go 1.26+
• Dependency: github.com/tetratelabs/wazero (see go.mod).

Usage

// One-shot: paths are relative to the process working directory.
out, err := exiftool.Command(nil, "-json", "photo.jpg")

// Explicit tree at /work (e.g. tests or isolated FS).
out, err := exiftool.Run(ctx, os.DirFS("/path/to/photos"), "-json", "/work/photo.jpg")

// Batch: one WASM/Perl startup, many commands.
e, err := exiftool.NewServer("-fast")
if err != nil { /* ... */ }
defer e.Shutdown()
out, err = e.Command("-Artist", "photo.jpg")

Package docs, API details, and filesystem semantics (Command vs Run, temp dir, Arg1 / Config): run go doc -all or open pkg.go.dev.

Development

Tests

go test ./... -timeout 10m   # includes WASM tests; allow several minutes

Refreshing embed/ from zeroperl

The WASM module, Perl install prefix, and minified ExifTool script come from zeroperl. Follow that repository’s Build section (Docker or Apple Container): build the image, run the container, and copy /artifacts into a host directory (as shown there, e.g. ./output/).

From the build output directory, install these into this repo under embed/:

Artifact from zeroperl output	Path in go-exiftool
zeroperl.wasm	embed/zeroperl.wasm
perl-wasi-prefix/ (entire tree)	embed/perl-wasi-prefix/
exiftool.min.pl	embed/exiftool.min.pl

Use the zeroperl.wasm artifact (reactor with asyncify) unless you intentionally switch runtimes. If you disable ExifTool in zeroperl (BUILD_EXIFTOOL=false), you must supply exiftool.min.pl yourself.

zeroperl’s README also documents build arguments (PERL_VERSION, EXIFTOOL_VERSION, BUILD_EXIFTOOL, memory/stack, etc.). If you change PERL_VERSION, update the hard-coded PERL5LIB paths in exiftool.go and server.go so the version segment (e.g. 5.42.0) matches the tree under embed/perl-wasi-prefix/lib/.

License

See LICENSE. ExifTool and embedded components carry their own licenses under embed/.