Review PRs from inside your running app: switch branches from an in-page widget and compare worktrees side by side. Loopback-only, zero dependencies.
What's great
switching branches in a widget that's already sitting inside the running app, instead of tabbing out to a terminal and reloading, removes so much friction from reviewing a PR visually. the side-by-side diff with onion mode for catching subtle UI shifts is exactly the kind of thing that's tedious to do by eye normally, and zero external dependencies means it's an easy install to justify to a team.
What needs improvement
would like to see the security model spelled out more - specifically what stops another local process from hitting the same loopback port the sidecar daemon listens on and triggering a worktree switch or diff on a repo it has no business touching.
vs Alternatives
before this the alternative was just eyeballing the diff in the terminal or flipping between two checked-out copies of the repo in separate editor windows. neither actually shows you the running UI, just the code, so subtle visual regressions slip through until someone notices in staging.
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Agentic coding is making development and code review more efficient than ever – teams are shipping thousands of PRs in the time it would've taken to manually create a handful. With evals and verification, we're approaching an ideal world where 99% of PRs are written, evaluated, and reviewed entirely by agents.
But that last 1% – the 1% where we still want to personally experience how a new feature looks and feels before signing off on it – is where sidebranch lives. Sidebranch is a browser extension paired with a local sidecar daemon that lets you easily switch between git worktrees while your app is running locally, and compare different branches side by side within a dedicated diff shell. Your working tree, uncommitted changes and all, is never touched.
In-page branch switching
Pick any branch from the pill and it builds in an isolated worktree on its own dev server.
🖥️ Side-by-side diffs
Both panes live, plus blend and onion diff modes where UI changes are highlighted.
🧘 Framework agnostic
Next, Vite, Django, Rails, everything supported as long as it answers HTTP on a port.
📦 Zero dependencies
The entire tool is Node builtins, with no external packages or dependencies.
Ah, just what I needed! I have been struggling on using agents for design, and having a visual diffing tool definitely helps!
I recently have this new workflow where I ask agent to build a functional mock on a separate project. I would like to have a way for agents to verify if they are building to the agreed mock spec visually. Does it support having agents to inspect between the diffs visually and by element tree, so agents can use it to figure out if it is building to spec?
@simon_liang_1 Working on it! I've thought of adding a mode to make the diff state more easily accessible by agents
loopback only w/ zero deps means no security convo before i put it on a client project. how many worktrees run at once before my laptop gives up
Hi Cristobal! Awesome project. Are you considering also showing a code changes in your tool or is it purely visual/functionality compare?
Onion mode is the bit I'd actually use. Comparing two branches isn't the hard part though, picking which screen to open is. We ship 111 one click flows and an agent PR can quietly move something on any of them, so what I need is a list saying these 4 pages changed visually, go look at those. If the sidecar can walk routes and flag the ones that moved, that's the version I'd install.
the "loopback-only, zero dependencies" pitch reads as the security answer, but the part I'd want to poke at before installing this on anything client-facing is the boundary between the browser extension and the sidecar daemon itself - if the daemon is listening on a local port to serve worktree switches and diffs, what stops any other tab or local process from hitting that same port and triggering a branch switch or diff against a repo it shouldn't touch? loopback-only keeps the internet out, it doesn't automatically keep other things on your own machine out.