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Free Diff Checker & Merge Conflict Resolver

Compare two blocks of text or code and highlight the differences instantly.

About this tool

A professional-grade diff checker and merge conflict resolver that runs entirely in your browser. Compare two texts with character-level highlighting that shows exactly which words changed within each line - not just which lines differ. Navigate changes with keyboard shortcuts (J/K), collapse unchanged regions to focus on what matters, and use the visual minimap to see change density at a glance. For merge conflicts, paste your file with Git conflict markers (<<<<<<< HEAD / ======= / >>>>>>>) and resolve each conflict with one click: Accept Ours, Accept Theirs, or Accept Both. Navigate between conflicts, see side-by-side diffs with character-level highlighting, and copy the fully resolved output when done. This tool uses the Longest Common Subsequence (LCS) algorithm - the same foundation used by git diff - to compute the minimal set of changes. All processing happens locally in your browser with zero data sent to any server.

How to use

Step 1: Choose Diff Mode to compare two texts, or Merge Mode to resolve Git conflict markers.
Step 2: In Diff Mode: paste original and modified text (or drag & drop files), then click Compare.
Step 3: Toggle between Split and Unified views. Character-level changes are highlighted within lines.
Step 4: Click ← Keep Original or Keep Modified → on each hunk to build your resolved output.
Step 5: In Merge Mode: paste a file containing `<<<<<<< HEAD` conflict markers and click Parse Conflicts.
Step 6: Use ← Ours, Theirs →, or Both ⇄ to resolve each conflict. Navigate with ↑ Prev / ↓ Next.
Step 7: Press ? anytime to see all keyboard shortcuts. Copy the resolved output when done.

Frequently Asked Questions

This tool uses the Longest Common Subsequence (LCS) algorithm, the same foundation used by git diff. It finds the minimal set of additions and deletions to transform one text into the other.

Instead of just highlighting entire changed lines, the tool identifies the exact words within a line that differ and highlights them with stronger emphasis. This makes it much easier to spot small changes in long lines of code.

Switch to Merge Mode, paste your file containing Git conflict markers (<<<<<<< HEAD / ======= / >>>>>>>), and click Parse. Each conflict is shown as a card with Ours vs Theirs. Click Accept Ours, Theirs, or Both for each conflict, then copy the resolved output.

Press ? to see all shortcuts. J/K navigate between hunks or conflicts, 1 accepts left/ours, 2 accepts right/theirs, B accepts both in merge mode.

Yes. Drag and drop any text file onto the input areas to auto-populate them. This works in both Diff and Merge modes.

No hard limit, but very large texts (10,000+ lines) may take a moment to process due to the O(n×m) LCS algorithm. For extremely large files, command-line tools like git diff are recommended.

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