Free, browser-based utilities for everyday developer workflows

Compare two CSV files by key

Compare two CSV exports by a shared key column — id, email, or an order number — to see which rows are missing on each side, which values changed, and which keys are duplicated.

Open this example in CSV Join / Merge / Compare

Open the tool, then paste the sample input below. Everything runs locally in your browser.

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The problem

Comparing CSVs by row order is unreliable because sorts and inserts shift everything. Matching on a stable key column gives you an accurate picture: matched rows, changed cells, rows only in A, rows only in B, and duplicate keys.

Sample input

CSV A
id,name,status
101,Asha,active
102,Ravi,inactive
103,Meera,active
CSV B
id,name,status
101,Asha,active
102,Ravi,active
104,Kiran,active

Expected output

Comparison (key = id)
102  changed   status: inactive -> active
103  only in A
104  only in B
101  unchanged

Row 102 matches on key but its status changed; 103 exists only in CSV A; 104 exists only in CSV B.

How to do it

  1. Paste or load CSV A.
  2. Paste or load CSV B.
  3. Select the key column, such as id.
  4. Run the comparison.
  5. Review missing, changed, matching, and duplicate-key rows.

Common mistakes

  • Selecting the wrong key column.
  • Ignoring duplicate keys, which inflate matches and hide changes.
  • Leaving extra spaces in key values.
  • Different column names for the key across the two files.
  • Case-sensitive comparison of emails or codes.

Related tools

Related guides

FAQ

How do I compare two CSV files by ID?

Load both files, pick the id column as the key, and run the comparison to get matched, changed, only-in-A, and only-in-B rows.

Can I find rows missing from one CSV?

Yes. Rows present under a key in one file but not the other are reported as only-on-left or only-on-right.

Can I compare changed values?

Yes. For rows that match on the key, the tool highlights which columns changed and shows the before and after values.

What happens if keys are duplicated?

Duplicate keys are flagged. Resolve them first, because duplicates can inflate match counts and mask real differences.

Is CSV data uploaded to a server?

No. Parsing, joining, and diffing all happen in your browser.

CSV comparison runs locally in your browser. No file is uploaded.

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