How to Use Terser via CLI or Node.js API

Terser is a JavaScript mangler and compressor toolkit that shrinks variable names, removes whitespace and comments, and drops unused code. You can run it two ways: through the Command line for one-off files and build scripts, or through the Node.JS API when you need to minify code programmatically inside a tool or pipeline. Both paths expose the same core options, so the choice comes down to whether you want a shell command or a JavaScript function call.

Using the Terser CLI

The CLI is the fastest route for minifying a file or a directory of files.

Basic usage

terser input.js -o output.js

• Input: the source file you pass as the first argument.
• Action: Terser parses the file, applies mangling and compression, and writes the result.
• Expected result: output.js contains the minified code. If you omit -o, the result is printed to standard output.

Common options

A typical production command combines them:

terser input.js -c -m -o output.min.js --source-map "url='output.min.js.map'"

Verifying the result

After running, open output.min.js and confirm that whitespace and comments are gone and identifiers are shortened. If the file still looks unminified, the compressor or mangler flag was likely omitted.

Common snags

• Broken code after mangling: mangling renames identifiers, so code that relies on Function.prototype.name or string-based lookups can break. Disable mangling for those cases or exclude specific names.
• No output file: if you forget -o, the minified code goes to stdout and may scroll past in the terminal.

Using the Terser Node.js API

The API is the right choice when minification is part of a larger JavaScript program — a custom build step, a bundler plugin, or a server-side transform.

Basic usage

const { minify } = require("terser");

const code = `function add(first, second) { return first + second; }`;

minify(code, {
  compress: true,
  mangle: true,
}).then((result) => {
  console.log(result.code);
});

• Input: the source string as the first argument, and an options object as the second.
• Action: minify returns a promise that resolves to an object.
• Expected result: result.code holds the minified string. If minification fails, result.error is set instead.

Configuring compress and mangle

Both compress and mangle accept either a boolean or an options object for finer control:

minify(code, {
  compress: {
    drop_console: true,
    passes: 2,
  },
  mangle: {
    toplevel: true,
  },
});

• compress controls code-level optimizations such as removing unused statements.
• mangle controls identifier renaming; toplevel: true extends renaming to top-level names.

Handling the result

Always check for errors before using the output:

const result = await minify(code, { compress: true, mangle: true });

if (result.error) {
  throw result.error;
}

console.log(result.code);

Where to Find Full Documentation

Terser publishes dedicated references for both interfaces:

• CLI Docs — every command-line flag and its behavior.
• API Reference — the full options object for minify and related functions.
• Options — the shared list of compress and mangle settings.
• REPL — a browser playground for testing options against sample code before wiring them into a build.

The project also maintains a GitHub repository and a Stack Overflow community tag for questions. Because Terser is described as an industry-standard minifier, its options surface is broad; the REPL is the quickest way to confirm what a given flag does to your code before committing it to a build script.