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3-Way Diff & Merge

Three-way diff and merge tool with automatic conflict detection and resolution.

3 way merge toolthree way diffmerge conflict resolvertext merge online
Base (Original)0 lines
Version A0 lines
Version B0 lines

What is 3-Way Diff & Merge?

3-Way Diff & Merge is a free online tool for resolving conflicts between two different versions of a document by comparing them against a common base. It performs a line-based three-way merge, automatically accepting non-conflicting changes from either side and highlighting conflicts that require manual resolution. Perfect for merging code, configuration files, or any text content where two people have made independent edits.

Common Use Cases

Code Merging

Merge two branches of code changes against a common ancestor, resolving conflicts interactively.

Configuration Merging

Combine configuration file changes from multiple environments or team members.

Document Collaboration

Merge edits from two collaborators who independently modified the same document.

Version Conflict Resolution

Resolve version conflicts when syncing files across systems or repositories.

How to Use This Tool

  1. Paste the original (base) text into the Base panel
  2. Paste the first modified version into the Version A panel
  3. Paste the second modified version into the Version B panel
  4. Click Merge to compute the three-way diff and detect conflicts
  5. Resolve any conflicts using the Accept A, Accept B, or Accept Both buttons, then copy the merged result

Frequently Asked Questions

What is a 3-way merge?
A 3-way merge compares two modified versions of a file against their common base version. Changes that only appear in one version are automatically accepted, while conflicting changes (both sides modified the same region) are flagged for manual resolution.
How are conflicts detected?
Conflicts occur when both Version A and Version B modify the same region of the base text differently. The tool highlights these regions and lets you choose which version to keep.
Is my data secure?
Yes! All merging and diffing happens entirely in your browser. No data is sent to any server.
Can this handle large files?
The tool works well for typical text files. Very large files (thousands of lines) may take a moment to process since the LCS-based diff algorithm runs in the browser.

Related Tools

Text Diff → JSON Diff →

3-Way Diff & Merge is a free online tool that requires no signup or installation. It works directly in your browser, keeping your data private and secure.