A native git diff viewer for macOS, built in Go with MyGo.

Browse uncommitted changes, compare a branch, or read any commit's files. Follow definitions in the working tree, ask Codex about the code, and commit and push from the same window. Peek refreshes as repositories change and remembers where you left each one.

Read the selected commit, uncommitted changes, or branch comparison as a stack of diffs, with changed files on the left and history on the right. Switch between unified and side-by-side views, mark files as viewed, and step through changes across files.

Browse every file at the selected commit or in the working tree. Related files are nested together; images and Markdown have previews, and Go, TypeScript and Kotlin files in the working tree support definition lookup.

To run from source, use macOS, Go 1.27.3 or later (as specified in go.mod), and git on your PATH. From this checkout:

go run . path/to/repository

Without a path, Peek opens the repository you are in, or restores the repositories open when it last quit. Use File → Open Folder (⌘O) to open another repository, and the project name in the toolbar to switch between them.

Build Peek.app and a .dmg into build/:

go tool mygo build

Use go tool mygo build -skip-dmg to build just the app.

Optional tools enable additional features:

• Uncommitted changes at the top of the history, alongside commits and branch comparisons.
• Changed files grouped into code, tests, docs and generated files, with added and deleted line counts. Tests, docs and generated files start folded as viewed; selecting one opens its diff.
• Syntax highlighting, folded unchanged lines and imports, unified or side-by-side diffs, and a patch fallback for files too large to display whole.
• File-path filtering, in-file search, Next / Previous Change, and Back / Forward navigation between definitions.
• Related files nested in Files using bundled antfu/vscode-file-nesting-config rules. Expand a file's arrow for its companions, or select its name to read it. Nesting works offline, within each directory.
• Image and Markdown previews, with a source toggle for Markdown and support for repository images.
• File and folder icons from the active VS Code icon theme when it provides SVGs, with file-icons as a fallback.

• Select line numbers to copy code references or GitHub links. Add comments from the gutter and copy them as an agent prompt.
• Ask Codex about the selected changes, starting from Explain, Review, Summarize or Suggest Tests, or your own question. Conversations are saved per repository and support follow-up questions.
• Review findings appear under the relevant diff lines, with the full result in the conversation.
• Ship stages all changes, asks Codex for a commit message following the repository's style, commits and pushes.
• Switch branches or check out a pull request from the branch name in the toolbar.
• Browse author and co-author avatars, commit details, linked issue and pull request references, and the branch's GitHub page or pull request.

• One shared window with per-repository state, restored on the next launch.
• Background fetches, incoming commit counts, and one-click fast-forward pulls. Fetches pause while offline or on a metered connection.
• Show in Menu Bar replaces the Dock icon with a menu of recent repositories, changed-file counts and commits to pull; right-click its icon to bring Peek forward.
• Hide When Inactive hides Peek when another app comes forward. Incoming commits are also counted on the Dock icon when it is shown.
• Notifications when shipping or a review finishes in the background, native macOS menus and controls, and system light and dark appearance.

In Files, choose Uncommitted Changes in the history, then ⌘-click a function, type or variable, or use Navigate → Go to Definition (F12). Hold ⌘ over an identifier to underline it and show a pointing hand before clicking. This offers a lookup; the language server resolves its definition. Go, TypeScript (.ts, .tsx, .mts, .cts) and Kotlin (.kt, .kts) use local language servers:

go install golang.org/x/tools/gopls@latest
npm install -g typescript-language-server typescript@6
brew install JetBrains/utils/kotlin-lsp

The TypeScript language server currently uses TypeScript 6's tsserver; TypeScript 7 does not provide that server. Peek prefers a language server in the repository's node_modules/.bin, then searches PATH. It also looks in ~/.local/bin and ~/go/bin. Node.js and Go must be available to the servers. Missing servers are reported when a definition is requested; Peek does not download them automatically.

Kotlin uses JetBrains' Kotlin Language Server over stdio. Peek finds the enclosing Gradle or Maven project, including builds in repository subdirectories. The first lookup waits for the server to import and index it. The project's JDK and Gradle/Maven wrapper (or installed build tool) must be available. Kotlin targets must be files on disk; virtual or JAR source locations are not supported. The server's Android support is experimental and Kotlin Multiplatform support is still under development.

A single definition opens directly; multiple definitions offer a choice. Standard libraries and dependency files open read-only, even outside the repository. The arrows in the file bar and Navigate → Go Back / Go Forward return to earlier positions. Historical commits and the branch comparison do not offer definition lookup. Servers start on demand, restart after a repository refresh to discard stale project information, and stop when the project closes.

Click Ask Codex in the toolbar to enter a question. The Shortcuts menu offers Explain, Review, Summarize and Suggest Tests; choose one and edit its request before sending. The scope shown beside Send tells you which changes the request concerns. Return sends the request; Shift-Return adds a line break.

Answers stream into a conversation. Use the Conversation Navigator to reopen saved conversations, continue with follow-up questions, copy a response or a whole conversation, or delete a conversation. Repository → New Conversation (⇧⌘A) starts a new one. Conversations are kept per repository across launches.

Questions and explanations use the selected history entry: uncommitted changes, a commit, or the branch comparison. Repository → Explain Changes (⇧⌘E) starts an explanation directly. Codex reads the diffs and surrounding code in a read-only sandbox using your existing login and settings. The toolbar shows progress and lets you stop the current request.

Choose the Review template in Ask Codex, or use Repository → Review Changes (⇧⌘R). When the branch comparison is selected, Peek reviews that comparison. Otherwise it reviews staged, unstaged and untracked changes; with a clean working tree, it reviews commits not yet pushed to the configured push destination. A new branch is compared with the remote's default branch, falling back to main or master when needed. Remote refs are those known locally.

The result appears in the conversation, and the toolbar shows Passed, Not Passed or Review Error. Any P0–P2 finding fails the review; P3 findings alone still pass. Findings also appear beside the affected diff lines. You can copy the result or ask follow-up questions in the conversation.

Peek checks that the reviewed changes still match the snapshot. Changing them makes the result stale and stops a review still running. Run Review Changes again for the new version. Dirty submodules, including untracked files inside them, must be committed or cleaned before reviewing.

Review leaves the index and working tree unchanged. It is independent of Ship: a failed review does not prevent a later push, but review and shipping cannot run at the same time.

Click Ship in the toolbar (⌘P) to stage all changes, including untracked files that Git does not ignore, write a commit message with Codex, commit and push. Peek supplies the staged diff and recent commit subjects so the message follows the repository's style. Commit messages use a separate small-model configuration; reviews and conversations use your Codex settings.

Before committing, Peek verifies that the branch, HEAD and staged tree have not changed. It fetches the remote before committing and pushing. If the remote explicitly rejects the push because the branch is protected, Peek creates and switches to a peek/push-… branch and pushes that instead. A detached HEAD also gets a new branch. With no new changes, Ship pushes existing commits without calling Codex. Git's push-remote settings are respected; otherwise Peek uses origin or the only configured remote. Ship does not create a pull request.

The button shows progress and can cancel an operation in progress. Failures show an alert; staged changes and any local commit are retained for a retry. Authentication, network and non-fast-forward failures stop the operation. Peek does not force-push or automatically merge.

go tool mygo vet .
CGO_ENABLED=0 go test ./...

With gopls and typescript-language-server installed, PEEK_LSP_TEST=1 go test ./internal/definition also checks real cross-file, TypeScript path-alias and standard-library definitions. With kotlin-lsp, Maven and a JDK installed, PEEK_KOTLIN_LSP_TEST=1 go test ./internal/definition checks real Kotlin cross-file function and type definitions, including UTF-16 and CRLF positions.

The screenshots show Peek browsing Dify in light and dark appearance. Regenerate them in docs/ using the installed app and a local Dify clone:

scripts/screenshots.sh path/to/dify

The script creates a temporary clone at commit 9dc53da, with origin/main 58 commits ahead, and captures Changes and Files (with dify-agent-runtime/internal/agentcli/config.go selected). It requires Screen Recording permission and control of System Events to switch appearance. Peek's saved projects, window state and the system appearance are restored afterward.

The performance tests time opening a project, scrolling its diffs, resizing the window and following its files, over repositories made for them, and scripts/perf/compare.sh times Godiff and Codiff over the same ones; docs/performance.md tells what they found:

PEEK_PERF=1 go test ./internal/app -run '^TestPerf' -v
scripts/perf/compare.sh

MIT. The icon fonts in internal/fileicons/fonts keep their own licenses, listed in its NOTICE.