c8

What c8 is

c8 is a free, open-source command-line tool that creates code coverage reports from Node.js’ built-in V8 coverage. It supports JavaScript, TypeScript, and JSX, and measures lines, functions, branches, and statements. Its reports work with Istanbul-compatible reporters; an experimental Monocart option includes v8 and console-details reporters. You can configure c8 with command-line flags, a c8 section in package.json, or a JSON file. The --all option adds eligible source files the engine did not load and marks them at 0% coverage. Source maps can connect coverage from generated code to original files, using inline or separate map files. Special c8 comments can exclude a line, a chosen number of lines, or a block. You can set coverage thresholds, including per-file checks, and have tests fail when coverage falls short. The README shows installing c8 globally with npm and running it with a Node.js script. The repository identifies its license as ISC. The latest listed release, v12.0.0, says its dependencies require Node.js ^20.19.0, ^22.12.0, or >=23.

Who it suits

c8 suits developers working with JavaScript, TypeScript, or JSX who want coverage reports from Node.js’ built-in V8 coverage. It is also relevant to projects that need configurable report formats, source-map remapping, or coverage thresholds that can fail tests.

Getting started

1. Open the c8 GitHub repository.
2. Install c8 globally with npm, as shown in the README.
3. Run c8 with a Node.js script.
4. Set options with command-line flags, package.json, or a JSON configuration file.

Verdict

Choose c8 if you need a free command-line tool that turns Node.js V8 coverage into configurable reports and can enforce coverage thresholds. Look elsewhere if you need pull-request annotations or historical trends, or if your platform is not Linux.