Percy vs SnapDiff

Percy automates visual testing by capturing DOM snapshots and assets, rendering them across browsers, and comparing results with earlier snapshots to flag visual changes. Responsive checks use configurable widths, while snapshot stabilization freezes animations and other dynamic elements to reduce false positives. Percy groups snapshots into the same build when tests run in separate processes or on different machines. Its review workflow includes status updates, notifications, comments, comparisons, and automatic diff matching. Listed integrations include GitHub, GitLab, Slack, Storybook, WebdriverIO, and Jenkins. Documented frameworks include Selenium, Playwright, Cypress, Puppeteer, Ember, Appium, and others. Percy documentation describes testing across real devices and desktop and mobile browsers. The free plan includes 5,000 screenshots per month, unlimited users, and unlimited projects. Desktop costs $199 a month, billed annually, for 10,000 screenshots per month; Desktop & Mobile costs $599 a month, billed annually, for 25,000 screenshots per month. Paid plans have fixed screenshot allowances, and additional usage is charged at the overage rate. Enterprise pricing is custom and unlisted.

SnapDiff captures web pages and compares screenshots pixel by pixel to identify visual regressions. Its HTTP API can compare two URLs without a test suite or CI/CD pipeline, and each diff returns a percentage, a highlighted image, and bounding boxes around changed regions. A GitHub Action runs visual checks on pull requests and can discover Vercel preview URLs. For scheduled monitoring, the watch API checks URLs on a cron schedule and sends webhooks when changes exceed a threshold. Comparisons use pixelmatch with antialiasing detection, configurable thresholds, ignore regions, and CSS selector masking. SnapDiff accepts HTTPS preview, staging, Storybook, and deployment URLs, including those on Vercel, Netlify, and Cloudflare Pages. Its MCP server supports Claude Code, Cursor, Windsurf, and other MCP clients for verifying UI changes. The service says it hides more than 40 cookie banners and 20 chat widgets and blocks more than 30 ad and tracker domains during capture. Free includes 200 diffs and 2,000 screenshots per month; paid plans start with Dev at $19 a month. Screenshots and diff images are retained during a subscription and for 30 days afterward.