How to view a Jest LCOV coverage report online

Jest generates an LCOV report at coverage/lcov.info when you run tests with --coverage and have 'lcov' in your coverageReporters list. The built-in HTML report requires a local browser and is lost after CI runs. This guide shows how to view that report online using the quickhelp.dev LCOV Coverage Viewer — paste or upload the file and immediately see which files have low coverage, sortable by percentage. No install, no sign-up, runs entirely in your browser.

Step-by-step guide

1. Run Jest with LCOV output: In your jest.config.js, set coverageReporters: ['lcov', 'text'] and run npx jest --coverage. The file coverage/lcov.info is created in your project root.
2. Upload to the viewer: Open quickhelp.dev/lcov-viewer and drag coverage/lcov.info onto the upload area. The file is parsed instantly in your browser.
3. Find uncovered files: The file table lists every source file. Sort by Line Coverage ascending to see the worst-covered files first. Red bars highlight files below 60% coverage.

Frequently asked questions

How do I enable LCOV output in Jest?

Add coverageReporters: ['lcov'] to your jest.config.js, or pass --coverageReporters=lcov on the command line. Run jest --coverage to generate the report.

Can I view coverage from a CI run?

Yes — download the coverage/lcov.info artifact from your CI pipeline (GitHub Actions, GitLab CI, etc.) and upload it to the viewer.