Key Takeaways
- CSV Diff compares two CSV files by a key column and reports added, removed and changed rows.
- You get a match rate plus a downloadable diff in seconds, with no upload.
- Use it to verify exports, audit imports and keep records in sync.
- For reconciliation across many files, Flookup in Google Sheets adds fuzzy matching and merge workflows.
Introduction
Your CRM exports a customer list on Monday and again on Friday. Between the two, people joined, left and changed their details. Finding what changed by hand is slow and error-prone.
The free CSV diff tool does it in one click: load both files, pick a key column, and see exactly which rows were added, removed or changed. Open the CSV diff tool.
What CSV Diff Does
- Added: rows in file B that are not in file A.
- Removed: rows in file A that are missing from file B.
- Changed: rows present in both but with different values.
- Match rate: what share of file B matched file A by key.
Every category is listed in a colour-coded table, and the whole diff can be downloaded as a CSV.
Why a Key Column Matters
A diff only makes sense if you can say which row in file A "is" which row in file B. The key column is that identity, usually an ID, order number or email.
Rows sharing a key are treated as the same record, so the tool can tell you when that record's other values changed rather than simply treating everything as a new row.
Privacy First
Both files are parsed in a background worker in your browser. Nothing is uploaded, stored or logged, so you can safely diff customer data, payroll and vendor records.
How to Use It
- Load file A (the current version) and file B (the version to compare).
- Confirm the header row setting and choose the key column in each file.
- Press Compare and review the added, removed and changed rows.
- Download the diff CSV if you need a record of the changes.
When to Use a Diff
- Checking that a CRM or ERP export contains exactly what changed.
- Auditing an import: did every row land, and did any get changed?
- Keeping a product, user or inventory list in sync between two systems.
Beyond Two Files
The CSV diff tool compares two files on one key. When you need to reconcile many files, match on fuzzy keys or merge duplicate records, the Flookup Data Wrangler add-on brings matching and merge workflows directly into Google Sheets. See the data cleaning tools for details.
Final Thoughts
A two-file diff is one of the most common data tasks there is, and it should take seconds, not a spreadsheet full of VLOOKUPs.