3-Way CSV Merge
Merge three versions of a CSV online. Match rows by key column, let independent cell edits combine automatically, and resolve only true conflicts. No upload.
Files never leave your browser.
About 3-way CSV Merge
Resolves CSV conflicts the way git does for code: three inputs (base + ours + theirs), keyed merging at the row level, with conflicts surfaced cell by cell where possible.
How to use
- Paste the common ancestor (base) CSV.
- Paste both edited versions into ours and theirs.
- Resolve conflicts row by row, optionally drilling in to choose individual cells.
Try a sample
A small inventory file with edits diverging from a shared base.
What this tool doesn't handle
- Requires a base version; if you only have two inputs, use Merge CSV.
- Schema changes (added or removed columns) are not auto-merged across sides.
Frequently asked questions
Do my files ever leave my browser?
No. Every comparison runs locally in your browser. Nothing you paste, drop, or load is uploaded to a server; the tool keeps working even if you go offline after the page loads.
Is this tool free to use?
Yes. All DiffResolver tools are free, with no account, sign-up, or installation. Because processing happens on your device, there are no server-imposed usage limits.
Can I resolve conflicts at the cell level?
Yes, where possible. When the two sides edited different cells of the same row, those edits merge automatically; when they edited the same cell, you choose the value for that cell directly.
What happens to rows deleted on one side?
A row deleted on one side and untouched on the other is removed automatically. If the other side also edited it, the tool surfaces a delete/edit conflict for you to decide.
Is there a file size limit?
No server limit applies, because nothing is uploaded. The memory of your device sets the practical limit. Above 10 MB for text, 40 MB for images, 100 MB for documents, or 500 MB for archives, the tool warns you that the work can be slow, but it never blocks the file.
Does this tool work offline?
Yes. The browser keeps a copy of the tool after the first visit, so a page you opened before still works without a network. You can also install DiffResolver as an app from the browser menu. Installation stays optional; the site works the same in a normal tab.
Where is my data stored?
Your files are stored nowhere. They stay in the memory of the page and are gone when you close the tab. Only what you save yourself stays in this browser: a snapshot, your tool options, and your theme. To remove it, open Settings and select Clear all local data.