See exactly what breaks when you migrate

Comparely is a free desktop application that tests website migrations by comparing a source site against a target site across three dimensions: page existence (HTTP status codes), content accuracy (titles, headings, body text), and visual regression (pixel-level screenshot comparison).

Comparely takes full-page screenshots of both source and target URLs using a headless browser, then compares them pixel-by-pixel using the Pixelmatch algorithm. Any differences above the configurable threshold (default 0%) are flagged, and a visual diff overlay highlights exactly where changes occurred.

Comparely runs on macOS (Intel and Apple Silicon), Windows (64-bit), and Linux (AppImage). The macOS version is code-signed and notarized for seamless installation. All platforms receive the same features and updates.

Yes, Comparely is completely free for personal use. There are no usage limits or telemetry. Commercial use requires a license — visit comparely.turn3.com for details.

When you enter a source URL, Comparely checks for a sitemap at the standard location (/sitemap.xml). It parses the sitemap to discover all pages automatically, then maps each source URL to its corresponding target URL based on the path structure. You can also manually provide a list of URLs to compare.

Download Comparely, enter your old (source) and new (target) site URLs, and run the existence check. Comparely automatically crawls both sites and compares HTTP status codes page by page. It flags 404 errors, broken redirects, redirect loops, authentication walls, and server errors — giving you a clear list of every broken page before your users encounter them.

Comparely's content comparison mode checks every SEO-critical element: title tags, meta descriptions, H1-H6 headings, and body text. It compares the source and target versions of each page and flags any differences using a 90% word-overlap threshold. This catches missing meta descriptions, altered titles, removed headings, and content drift that could harm your search rankings.

Yes. Comparely takes full-page screenshots of both source and target URLs and compares them pixel-by-pixel using the Pixelmatch algorithm. You can configure the visual diff threshold (default 0%) to control sensitivity. The interactive report shows source, target, and diff overlay views so you can see exactly what changed visually.

Manual QA requires clicking through pages one by one, comparing content in spreadsheets, and visually inspecting layouts — a process that takes days for large sites and misses subtle regressions. Comparely automates all three checks (existence, content, visual) across your entire site, processing 50 pages per batch. It catches broken redirects, content drift, and CSS regressions that manual testing routinely misses.

Comparely supports HTTP basic authentication for both source and target sites. Click the lock icon next to each URL field to enter credentials. Your session is preserved across all page requests during the comparison.

Comparely uses the Pixelmatch algorithm for pixel-perfect comparison. The default threshold is 0% (any pixel change is flagged). You can adjust the visual sensitivity slider from 0% to 100% to tolerate minor differences like anti-aliasing or font rendering variations across environments.

Yes. Comparely uses Playwright, a headless browser that fully renders JavaScript-driven pages before capturing screenshots and extracting content. If your SPA has a sitemap or discoverable URLs, Comparely can test it.

Comparely generates interactive HTML reports that you can save and share. Reports include pass/fail summaries, detailed diffs, side-by-side screenshots, and content comparisons — all viewable in any browser without installing the app.

BackstopJS focuses only on visual regression — it doesn't check page existence or content accuracy. Percy is a paid SaaS service with cloud-based screenshots. Comparely is free, runs locally, and covers all three dimensions: existence, content, and visual regression in one tool.