Code coverage badge and history chart without Codecov

buildstats takes the coverage percentage your tests print and serves a README badge, a per-commit chart and a pull request comment with the delta. Free for public repos, no signup; private $9/month per owner.

Codecov and Coveralls parse your coverage report, which gives line-by-line views and patch coverage. Badge actions commit an SVG to the repository or a gist, which gives a badge and nothing else. buildstats does the middle thing: a number in, and out come a badge, a chart and a pull request delta, with no report upload and no commit to your repository.

Setup: extract the percentage, push it

Every coverage tool prints a total. The example uses a JSON summary from Istanbul or Vitest; the jq line is the only thing that changes for other tools.

name: Test

on:
  push:
    branches: [main]
  pull_request:

permissions:
  contents: read
  id-token: write
  pull-requests: write

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npm ci && npx vitest run --coverage --coverage.reporter=json-summary

      - id: cov
        run: |
          echo "lines=$(jq '.total.lines.pct' coverage/coverage-summary.json)" >> "$GITHUB_OUTPUT"
          echo "branches=$(jq '.total.branches.pct' coverage/coverage-summary.json)" >> "$GITHUB_OUTPUT"

      - uses: bitgate/buildstats@v1
        with:
          metrics: |
            coverage=${{ steps.cov.outputs.lines }} % higher
            branch_coverage=${{ steps.cov.outputs.branches }} % higher
          max-regression: 1

Other tools: coverage.py prints the total with coverage report --format=total; go tool cover -func ends with a total: line; cargo llvm-cov --summary-only --json has .data[0].totals.lines.percent; JaCoCo's XML has counters you can sum with xmllint; simplecov writes .last_run.json with result.line. The direction higher makes a drop show as worse, and max-regression: 1 fails the step when coverage falls more than 1% below the base branch.

The badge

![coverage](https://buildstats.io/acme/app/coverage/badge.svg)

The badge is a 20-pixel SVG in the shields.io flat style showing the latest value on the default branch, for example "coverage 87.2%". It updates by itself after each push; public badges are cached for 5 minutes. /coverage/badge.json serves the same number in the shields.io endpoint format, for a badge rendered by shields.io with your own colours and logo. ?ref=release shows a different branch.

The chart and the pull request comment

<picture>
  <source media="(prefers-color-scheme: dark)" srcset="https://buildstats.io/acme/app/coverage.svg?theme=dark">
  <img alt="line coverage per commit" src="https://buildstats.io/acme/app/coverage.svg">
</picture>

The chart shows up to 1,000 of the 50,000 points a metric can hold, 400 to 1,200 pixels wide, in light and dark. On pull requests the Action compares the coverage with the latest value on the base branch and posts one comment with the base value, the new value and the delta. The comment is kept up to date across pushes and matrix legs. With max-regression set, the step fails after the comment is written, so a required check blocks the merge while the numbers stay visible.

Coverage per package pushes as variants: variant: ${{ matrix.package }} stores coverage/api and coverage/web, which overlay on one chart and get separate rows in the comment.

Limits and pricing

Everything else is on the pricing page.

How this compares

Choose Codecov or Coveralls when reviewers need to see which lines a pull request left uncovered. Choose a gist or committed badge when the badge is all you want and a bot commit per run is acceptable. Choose buildstats when you want the badge, the per-commit chart and the pull request delta from one number and no uploads.

Last updated 2026-10-07.