CLI Usage

@catlabtech/webcvt-cli provides a command-line interface for one-off file conversions without writing any code.

Installation

# Run directly without installing (recommended for scripts)
npx @catlabtech/webcvt-cli [options] <input> <output>

# Or install globally
npm i -g @catlabtech/webcvt-cli
webcvt [options] <input> <output>

Basic usage

# Convert an image
npx @catlabtech/webcvt-cli photo.jpg photo.webp

# Convert a subtitle file
npx @catlabtech/webcvt-cli subtitles.srt subtitles.vtt

# Convert audio
npx @catlabtech/webcvt-cli song.wav song.mp3

The output format is inferred from the output file extension.

Piped usage

Use - as the input path to read from stdin, and specify --from to declare the input format:

# Read from stdin, write to file
cat photo.png | npx @catlabtech/webcvt-cli --from png - photo.webp

# Pipe between tools
curl -s https://example.com/video.mp4 | npx @catlabtech/webcvt-cli --from mp4 - out.webm

Options

Option	Description
--from <ext>	Force input format (overrides auto-detection)
--quality <0-1>	Quality hint, 0.0–1.0 (default: 0.85)
--help	Show help
--version	Print version

Supported format pairs

The CLI delegates to registered backends. The available conversions depend on which backend packages are installed. Common pairs:

Input	Output
jpg, png, webp, bmp, ico	jpg, png, webp, bmp, ico
gif, apng	gif, apng, webp (animation)
svg	png, jpg, webp
srt, ass, ssa	vtt, srt, ass
wav, mp3, flac, ogg	wav, mp3, flac, ogg (via WASM backend)
mp4, webm, mkv	mp4, webm, mkv (via WASM backend)

Error handling

The CLI exits with code 1 on conversion failure and prints a human-readable message to stderr:

npx @catlabtech/webcvt-cli bad.xyz out.png
# stderr: Error: Unsupported input format: "xyz"
# exit code: 1

For scripting, check $? after each invocation.