Free 3-Way Diff Viewer

Three-way diff compares a base version with two modified versions, helping identify conflicts like in git merges.

Yes, line numbers are shown for all panels for easy reference.

Yes, completely free.

Absolutely. The 3-Way Diff Viewer processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the 3-Way Diff Viewer is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the 3-Way Diff Viewer in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

The 3-Way Diff Viewer works in all modern browsers including Chrome, Firefox, Safari, Edge, and Opera. For the best experience, use the latest version of your preferred browser.

A 2-way diff compares one Original against one Modified version and answers a single question: what changed between these two snapshots? It is the everyday "before and after" view. A 3-way diff adds a common ancestor, called the Base, and compares it against two independent edits, Version A and Version B. Because both versions are measured from the same starting point, a 3-way diff can tell which side touched which lines and whether the two edits collided on the same region — exactly the logic Git uses to detect a merge conflict. This tool offers both with a single toggle. Use 2-way mode to review a straightforward revision, and 3-way mode when two people changed the same file separately and you need to see who did what. Switch modes above and paste your versions to compare instantly.

The viewer computes differences with the Longest Common Subsequence (LCS) algorithm, the same line-matching approach behind classic Unix diff and Git. LCS finds the longest run of lines the two inputs share in the same order, then treats everything outside that run as either inserted or deleted. The benefit is alignment: instead of reporting an entire file as rewritten when a single line moves, it keeps the unchanged lines lined up and flags only the genuine edits in green for additions and red for removals. The comparison is line-based, so each input is split on line breaks and every line is matched as a whole unit rather than character by character. That makes it well suited to source code, Markdown, CSV rows, logs, and config files. Paste your two versions and the highlighted result appears the moment you stop typing.

Unified diff is the standard patch format used by Git, code review tools, and the Unix patch command. It opens with two header lines marking the old and new files (--- and +++), then groups changes into hunks introduced by an @@ marker showing line positions. Inside each hunk, lines prefixed with a plus sign were added, lines with a minus sign were removed, and unchanged context lines carry a leading space. The reason to copy it is portability: a unified diff is plain text that any developer or tool can read and apply, so you can drop it straight into a pull request comment, a bug report, or a .patch file without screenshots. This tool builds the unified output automatically from your panels, and a one-click Copy button puts it on your clipboard. Paste your versions, then copy the unified diff when you are ready to share the change.

Yes — the 3-way mode mirrors exactly how a merge conflict is structured. A conflict happens when two branches edit the same file independently, and Git compares both against their shared ancestor to decide which changes can combine and which collide. Switch to 3-way diff, paste the common ancestor into Base, your branch into Version A, and the incoming branch into Version B. The viewer shows all three columns with separate change counts for Base to A and Base to B, so you can see at a glance which side touched which lines and where they overlap. From there you can decide line by line which edits to keep when you resolve the conflict in your editor. Note this is a read-only comparison aid: it helps you understand the conflict but does not commit, stage, or write files. Paste your three versions above to map out the merge before you fix it.

There is no fixed character or file-size cap, and no paywall that unlocks bigger inputs — you can paste short snippets or long files into the panels. Because the diff runs entirely in your browser using the LCS algorithm, performance depends on your own device rather than a server queue, and most realistic inputs like source files, config snippets, logs, or document drafts compare effectively instantly. The one practical consideration is that LCS work grows with the size of both inputs, so comparing two very large files of many thousands of lines can take a moment longer than a small snippet. For typical code reviews and revision checks you will not notice any delay. Nothing you paste is uploaded, so even confidential patches or contracts stay on your device. Paste your text into the panels above and the highlighted diff appears as soon as you finish.