sidebranch

What sidebranch does

sidebranch is an MIT-licensed local tool for reviewing web application branches in running browsers. It starts a loopback-only daemon, creates persistent review environments with git worktree, and launches each branch on its own development server. The primary working tree, including uncommitted changes, is not checked out, reset, or stashed. A Chrome or Edge extension adds a control to localhost pages; Firefox and Safari users can inject the daemon's development-only widget script.

Its comparison shell offers live side-by-side panes with shared 375, 768, and 1280-pixel viewport presets. Blend mode uses CSS difference blending so changed pixels glow; layer mode supplies an opacity slider. A local frame proxy removes only restrictive framing headers from pane responses so apps on different localhost ports can be embedded. Production responses and original pane ports stay unchanged.

Setup and pricing

Run npx sidebranch init, edit .sidebranch.json, and run npx sidebranch start. Configuration supports one to four panes, custom development and install commands, copied local files, environment overrides, readiness probes, and a base port. Dependencies reinstall only when a lockfile content hash changes. Documented recipes cover Next.js, Vite, Django, Rails, and static sites. The daemon uses Node built-ins and has zero runtime dependencies.

sidebranch is free open-source software under the MIT license. The required pricing fetch returned no usable commercial page, so this record remains flagged for manual verification. Local compute, dependency storage, and setup time are the practical costs. The repository showed five GitHub stars during research, making this an early project that deserves stack-specific testing.

Strengths and limitations

The best use case is visual pull-request review when screenshots are too static and hosted previews are too slow. Worktrees protect the main checkout, while doctor, stop, and clean commands cover lifecycle management. Loopback binding, authenticated requests, origin checks, and a widget that refuses to run outside localhost are sensible safeguards.

Limits are concrete. sidebranch runs one process and varies one port per pane, so databases, emulators, proxies, and workers on fixed ports must run once as shared services. Scroll and interaction synchronization are out of scope. Firefox and Safari require script injection, which strict Content Security Policy can block. Copying broad environment files into review worktrees can duplicate unnecessary secrets; include only what each branch requires.

Compare GitHub MCP Server, Cursor Agent, CodeRabbit, and the AI coding agents comparison. Choose sidebranch for “did this branch change the rendered interface?” Keep conventional review, tests, accessibility checks, and hosted previews for production confidence.