Merge CSV Files
Merge two CSV files online. Rows are matched by key column; pick the winning side for each difference and export the combined table. Nothing is uploaded.
Files never leave your browser.
About CSV Merge
Walks the differences between two CSVs and lets you pick which side's row wins on a per-key basis. Useful when two collaborators edited the same spreadsheet export.
How to use
- Load both CSV files.
- Set Key columns so rows can be matched by identifier rather than position.
- For each conflicting row, pick a side and export the merged CSV when done.
Try a sample
A user roster with role and name edits. Pick a side per user.
What this tool doesn't handle
- Cell-level merging within a single row is not supported. You keep one whole row.
- Numeric and date formatting differences are treated as text differences.
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.
How are rows matched between the two CSV files?
By the Key columns you configure, typically an ID column. Rows with the same key are paired, and you decide which side's version wins for each conflicting row.
Can I merge individual cells instead of whole rows?
Not in the two-way merge; you keep one side's entire row. 3-way CSV Merge can resolve conflicts cell by cell when a base version is available.
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.