Left Right - File Compare

Left Right is a native macOS file compare and merge app. It shows what differs between two files or folders and lets you bring across only the changes you want.

■ Compare two files side by side
- Two panes with corresponding lines aligned and synchronized scrolling
- Line numbers, difference markers (+ − ~), difference coloring, in-line highlights, a center difference gutter, and difference marks on the scroll bar
- Copy a difference from left to right or right to left, hunk by hunk. Also available from the keyboard, and every copy can be undone
- Type, delete, cut, copy, paste, undo/redo, and find in pane (Cmd-F)
- Ignore whitespace, letter case, blank lines, and Unicode normalization differences. Presets are available, and "Custom" is shown when the current mix does not match one
- Text encoding and line endings are detected automatically and preserved on save. When the two sides disagree, Left Right reports it separately from content differences
- Convert either text pane to LF, CRLF or CR with undo/redo. Save As writes edited text to another file so you can keep comparing the saved file
- If a file changes on disk after the comparison starts, you are told before saving
- Recent comparisons are remembered as bookmarks. An expired bookmark is kept in gray with a "Grant Access…" button rather than being dropped

■ Compare folders
- Recursive scanning with a tree view (hierarchy or list)
- Compare modes: Smart, Contents, Metadata, Bytes. Five filters plus a default ignore list and regular-expression rules
- Copy items that exist only on one side. Existing items are moved to the Trash before an overwrite
- Copying can follow the Finder (default), merge, or replace

■ Merge three versions
- Combine left and right that diverged from a common base. Left, base, and right on top, the result below
- Separate changes merge automatically; overlapping changes stay in the result as git-compatible conflict markers
- Resolve each conflict with "Use Left", "Use Right", "Use Both", or by hand

■ Compare tables, binaries and images
- CSV / TSV and .xlsx / .ods / .numbers side by side, showing added, removed, and changed rows and which columns differ. Align columns by the header row and match rows by a key column
- Compare supported password-protected .xlsx / .xlsm / .ods files by entering their password. Passwords are not stored, and decrypted contents are not written to disk
- Binary comparison in hexadecimal at the same offsets, with a byte map and entropy strip on each side and byte classes in different colors
- Image comparison with six views (Side by Side, Overlay, Slider, Difference, Blink, Heat Map) plus a threshold. Differing pixels are grouped into numbered regions
- Export or copy a patch as Unified Diff with three lines of context

■ Getting around
- Select two items in the Finder and open the comparison from the Services menu ("Compare with Left Right"). Files or folders both work; anything other than exactly two items is refused
- Callable from git difftool / git mergetool. Help → "Git Integration…" has commands you can paste. Help also explains how to install the bundled Terminal command and Finder Quick Action
- Settings (Cmd-,) cover defaults for new comparisons, appearance (window colors, difference colors, syntax coloring), and keyboard shortcuts
- English and Japanese, and light and dark appearances, follow the system
- macOS 27 or later. Runs in the App Sandbox

■ No network, no collection
- The app does not communicate over the network (it has no network entitlement)
- No account is required, and no usage analytics or data collection
- It reaches only the files and folders you open or choose
- Text editing, hunk merges, and the three-way result do not touch the disk until you save. Folder merge changes the disk as it runs (existing items are moved to the Trash before an overwrite)
- File contents are never written to logs