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BackstopJS vs pixelmatch: open-source visual regression tools compared

Metrics as of , from the GitHub or GitLab API of each repository. Refreshed monthly.

Summary

BackstopJS: Visual regression testing tool that captures web app screenshots and compares them against approved references.

pixelmatch: JavaScript library for pixel-level image comparison with anti-aliasing detection, for Node.js and browsers.

Both are listed under Visual regression. The table gives repository metrics from the GitHub API with their fetch date, then the documented facts used for every comparison in this category, each linked to the README or docs page it comes from. A cell reads "not documented" when the fact was not found in the project's documentation (3 of 12 fact cells here); that does not mean the feature is absent.

Side by side

BackstopJS and pixelmatch: metrics and documented facts, in the fixed row order used for visual regression comparisons.
FactBackstopJSpixelmatch
Stars7,18116,9571
Forks62113281
Contributors1761191
Last release2019-01-2112026-04-291
Last commit2026-09-0812026-09-151
Commits in 90 days11111
LicenseMIT1ISC1
Primary languageJavaScript1JavaScript1
Statusactive1active1
BrowsersChrome Headless via Puppeteer; Chromium, Firefox, WebKit via Playwright source: READMEnot documentednot found in the project's documentation as of
Framework integrationsPlaywright and Puppeteer scripts for user interactions source: READMEnot documentednot found in the project's documentation as of
Test authoring formatJSON or JavaScript config file (backstop.json) with scenarios; onBefore and onReady scripts source: READMECode (JavaScript function on raw image data); CLI binary for PNG images source: README
CI integrationCI report for build systems such as Jenkins and Travis source: READMEnot documentednot found in the project's documentation as of
Report formatsIn-browser HTML report, CLI report, JUnit XML, JSON source: READMEDiff image output and a count of mismatched pixels source: README
Install methodnpm (npm install -g backstopjs) source: READMEnpm (npm install pixelmatch); browser import from a CDN source: README

1 Fetched from the GitHub or GitLab API on . Hover a value for its own date.

When each fits

Written from each project's documented scope, not from preference. Neither tool is ranked.

BackstopJS

Fits projects that run visual regression tests on web apps by comparing screenshots over time; its README describes rendering tests in a Docker container. source: README

pixelmatch

Fits projects that compare screenshots pixel by pixel from JavaScript code; its README describes anti-aliased pixel detection and perceptual color difference metrics. source: README

More on these tools

Sources

  1. GitHub REST API: repository, read
  2. GitHub REST API: repository, read
  3. GitHub REST API: contributors, read
  4. GitHub REST API: contributors, read
  5. GitHub REST API: latest release, read
  6. GitHub REST API: latest release, read
  7. GitHub REST API: commits, read
  8. GitHub REST API: commits, read
  9. README, read
  10. README, read

Documented facts collected 2026-09-22. See the methodology for how metrics and facts are gathered.