Stop pasting production configs into an online diff tool.
Compare two files, keep the ones worth keeping, and hand one to a teammate sealed —
with no account, no telemetry and not one network request.

Install · What it does · Offline by construction · Build · Docs

Install

OS	Get it
Windows 10/11	diff-bro-Setup-v<version>.exe
macOS 12+ (Apple silicon)	diff-bro-v<version>.dmg or Homebrew

brew tap mindaugaskasp/tap
brew install --cask diff-bro
xattr -dr com.apple.quarantine "/Applications/Diff Bro.app"

Builds are unsigned, so SmartScreen and Gatekeeper warn on first launch (the xattr line clears it on macOS) — see packaging.

What it does

Compare	Two files or pasted text, split or inline, word-level highlights, in-view search, and a live re-diff when a file changes on disk.
Understand structure	JSON, YAML and XML compared as data: reordering keys or reformatting stops counting, and unchanged keys collapse away.
Excel	.xlsx workbooks as aligned grids — sheet tabs and cell-level highlights, with inserted rows and columns that don't cascade into false changes. Dates read as dates, hidden sheets and rows are marked, and formulas are compared as well as their results, so a total pasted over the formula behind it is caught rather than shown as unchanged. Set a tolerance — one of the presets or a threshold of your own, percentage or raw — and rounding noise stops counting; export the whole change list as a CSV.
CSV	.csv and .tsv compare as text or, one toggle away, as the same grid — rows aligned by their first column, quoted fields kept whole.
Huge files	Past 32 MB a file is indexed by line instead of loaded, and the rows you're looking at are read from disk as you scroll — a multi-gigabyte log opens in seconds. Marked as streamed, with the few actions that need the whole text saying so rather than half-working.
Keep	Saved diffs: encrypted, tagged, optionally auto-expiring. Your open tabs come back on the next launch.
Share	One signed file only the recipients you ticked can open, carrying the expiry you chose so every copy dies at the same moment.
Export as image	A real screenshot of the diff view — your theme, panes and highlighting — cropped to the change and stitched if it's taller than the window. Snippets go the same way, and a Mermaid snippet leaves as its rendered diagram.
Snippets	An encrypted, tagged text library you can drag straight into the diff pane — two snippets compare like any two files, and editing one updates the comparison on screen. Per-language highlighting, live Mermaid (readable light or dark whatever the app is wearing), Markdown/Jira preview, and secret snippets that render as ****.
Quick look-up	A global shortcut searches your snippets and diffs without raising the app; copy one straight to the clipboard.
Diagrams	Two Mermaid files compare as a picture, not as text — one diagram carrying both revisions, so an inserted node reads as one change instead of a rewrite.
Tools	JSON, Base64, UUID, JWT, Epoch, URL, Lines, XML, checksums, a regex tester, find & replace, text encryption — rich panels, not blank text boxes.
Terminal	diffbro compare a.json b.json opens a comparison in the running app, diffbro open raises it, diffbro backup <path> writes an encrypted archive. No port, no daemon.
Yours to arrange	Fourteen themes (Nord, Sepia, Solar, Nyan, Matrix, plus accessibility-grade Contrast and Beacon), shared tags, adjustable limits.

The smaller things

• Drag & drop files onto the window; it warns before discarding unsaved work.
• Ctrl/Cmd+V pastes straight into a comparison — including pasted text against a real file.
• Copy diff puts a git-style unified patch on the clipboard.
• Quick look-up keys — ↑/↓ browse, → steps into a preview or the tools, ← steps back out, Enter opens, + captures a plaintext snippet without raising the app.
• Resizable dialogs — the snippet editor and tool windows resize from any edge and remember their size; existing snippets open read-only until you press Edit.
• Save a tool's output — anything a tool produced goes straight into the snippet library from its own window; you supply the name, the app fills the rest.
• Uniform snippet names — every name is sentence-cased on save, so a library grown over months still reads consistently.
• Repair a pasted diagram — Mermaid copied out of Word or Confluence arrives with —> where --> was, curly quotes and non-breaking spaces; Repair in the snippet editor puts them all back.
• More terminal commands — diffbro open [<file>] brings the app to the front (with a file, it fills the left side and waits for the right), diffbro backup <path> seals everything you have into a zip at a path you choose, diffbro create snippet opens a new snippet, diffbro cb save keeps what you just copied, and diffbro help <command> explains one. A second launch hands its arguments to the running window through Electron's single-instance lock.
• The tools in full — JSON (pretty/minify/sort, JSONPath filter, collapsible tree), Base64 (URL-safe, MIME wrap), UUID (v1/v4/v5/v6/v7, inspect, convert), JWT, Epoch, URL (editable query-param table), Lines (split, sort, dedupe, build a SQL IN (…) list), XML format + validate, find & replace, and AES-256-GCM passphrase encryption with an opt-in raw-key CBC decrypt for external payloads.

Offline by construction

flowchart LR
    subgraph pc["your machine — all of it happens here"]
      direction LR
      r["renderer<br>sandboxed · no Node"] <-->|"validated IPC"| m["main process<br>files · crypto · dialogs"]
      m --> v[("saved diffs · snippets · keys<br>AES-256-GCM")]
      m --> k[["OS keychain<br>holds the key"]]
    end
    m x-- "blocked" --x net(("the<br>internet"))

Loading

• Zero network — a session-level kill switch, a strict CSP, a deny-all permission handler and a blocked will-navigate, not just a promise.
• Encrypted at rest — AES-256-GCM, the key held by your OS keychain, and never handed to the renderer.
• Sealed sharing — sign-then-encrypt, bound to the exact recipient set, with an expiry capped at one week. Details in the security model.

A look around

Excel workbooks as aligned grids.	Fourteen themes, GitHub-style rendering.
Saved diffs are encrypted and auto-expire.	Drop or choose two files of any text format.
Mermaid files compare as a picture, not as text.

Build from source

Needs Node 22.12+ — the version Docker and CI use.

nvm use          # or install Node 22.12+ yourself
npm install
npm run dev      # run it
npm run check    # lint + tests

No local Node? The same flow runs in Docker: make dev, make check, make e2e (see docker/README.md and make help).

Electron · Vue 3 · Pinia · Monaco. New formats plug in through the adapter registry rather than into the viewer.

Docs

Doc	What's in it
Architecture	Processes, trust boundary, directory map
IPC & security	How renderer↔main talk, and what the sandbox blocks
Security model	Offline guarantee, sharing, keys, backup
Packaging	Installers, signing notes, CI
Chocolatey	Plan + package skeleton for choco install diffbro
Glossary	Every term and abbreviation (IPC, CSP, GCM, …)
Standards	Coding standards and the rules the build enforces

License

Mozilla Public License 2.0 — use it commercially and link it into proprietary code; changes to Diff Bro's own files stay open.