3-Way Diff & Merge Tool

Mode:
Base (Original)0 lines
Theirs (e.g., Claude's version)0 lines
Mine (Your edits)0 lines

Paste text into the panels above to perform a 3-way merge.

Tip: Use the Sample button to see how it works!

What This Tool Does

3-Way Diff & Merge Tool is built for deterministic developer and agent workflows.

3-way merge with conflict resolution — compare Base, Theirs, and Mine versions to resolve merge conflicts.

Use How to Use for execution steps and FAQ for constraints, policies, and edge cases.

Last updated:

This tool is provided as-is for convenience. Output should be verified before use in any production or critical context.

Agent Invocation

Best Path For Builders

Browser workflow

Runs instantly in the browser with private local processing and copy/export-ready output.

Browser Workflow

This tool is optimized for instant in-browser execution with local data handling. Run it here and copy/export the output directly.

/diff-merge-tool/

For automation planning, fetch the canonical contract at /api/tool/diff-merge-tool.json.

How to Use 3-Way Diff & Merge Tool

  1. 1

    Input three versions

    Provide the original (base) version, your version, and the incoming version. Paste each into its labeled section. The tool highlights changes, conflicts, and matches automatically.

  2. 2

    Identify conflicts

    Areas where all three versions differ are marked as conflicts. Blue sections show changes from the base, red shows conflicting edits. Green sections are merged cleanly.

  3. 3

    Resolve conflicts manually

    For each conflict, decide whether to keep your changes, accept the incoming changes, or manually combine them. Click through conflicts systematically, reviewing the context in each section.

  4. 4

    Export the result

    Once all conflicts are resolved, copy the merged version or download it as a file. Use this for code merges, document updates, or configuration reconciliation across branches.

  5. 5

    Use for non-code merges

    This tool is useful beyond git: merge YAML configs, JSON data structures, or documentation where git doesn't handle 3-way merging well.

Frequently Asked Questions

What is 3-Way Diff & Merge Tool?
3-Way Diff & Merge Tool performs three-way merges with conflict resolution. It compares Base, Theirs, and Mine versions to help you resolve merge conflicts — essential for version control workflows.
How do I use 3-Way Diff & Merge Tool?
Paste your Base version, the Theirs version (incoming changes), and your Mine version (local changes) into the three input panels. The tool detects conflicts and lets you choose which version to keep for each conflicting section.
Is 3-Way Diff & Merge Tool free?
Yes. This tool is free to use with immediate access—no account required.
Does 3-Way Diff & Merge Tool store or send my data?
No. All processing happens entirely in your browser. Your data never leaves your device — nothing is sent to any server.
When should I use 3-way merge instead of a regular 2-way diff?
Use 3-way merge when you have a common ancestor (Base) and two diverged versions. This is the standard scenario in Git merge conflicts. The Base version provides context about what each side actually changed, leading to more accurate and safer conflict resolution than a 2-way comparison.