Side by Side Browser

When you migrate or rebuild a website, you constantly need to compare the old and new pages. Lining up two browser windows and scrolling them by hand is slow and error-prone, and stacking pages in an <iframe> fails on most real sites because X-Frame-Options and CSP block embedding.

Side by Side Browser is an Electron desktop app that loads two web pages into two native webviews and keeps their scroll position and URL path in sync so you can compare them.

Features

• Two native webviews — real Chromium rendering, not iframes, so almost any page loads
• Scroll sync — move one pane and the other follows; pick the unit, px (apply the absolute pixel offset 1:1) or percent (map by scroll ratio)
• URL path sync — copies pathname / search / hash while keeping each pane's own origin, so old.example.com/products/42 lines up with new.example.com/products/42
• External-domain lock — blocks any navigation that changes the hostname (redirects included), pinning the session to your two sites
• Open links in a new tab — opens a clicked link in a fresh, path-synced tab across both panes
• Tabs — multiple comparison pairs in one window, wrapping onto multiple rows, with full keyboard control
• Persistent settings — the sync toggles and scroll unit are saved and restored on the next launch

Security

Built to load untrusted production / staging pages: context isolation on, node integration off, sandbox on, and permissions denied by default.

Stack: Electron / Chromium WebContentsView / Tailwind CSS v4. Distributable builds for macOS (arm64). MIT licensed.