Opselith
CSV TOOLKIT / COMPARE

Compare two CSV files

Choose two CSV or TSV files, match rows by one column, and see what is missing or different.

LOCAL PROCESSINGNO UPLOADUP TO 25 MB EACH
01 / FILES

Choose the two files

Choose two CSV or TSV files. Opselith checks the column names and helps you choose how to match the same row in both files.

FILE AChoose the first CSV or TSVUp to 25 MB · processed locally
FILE BChoose the second CSV or TSVUp to 25 MB · processed locally
✓ Local only. Both files stay in this browser. They are not uploaded or added to the URL.
02 / MATCH

Choose how to match rows

Choose a column with one value for each row in both files, such as an email address or employee ID.

WHAT TO EXPECTOpselith creates one comparison report. Your two files are not changed.

Rows are matched using the column you choose. You will see which rows exist in only one file and which values are different.

03 / REVIEW

Review the differences

Your comparison summary will appear here.

Only in File A0
Only in File B0
Found in both0
Changed rows0

StatusValue used to matchWhat changed
Run the comparison to review differences.
Your source files are never changed. Values that spreadsheet apps could treat as formulas are made safe in the downloaded CSV.
Back to CSV Toolkit
About CSV comparison

How rows are matched

The column you choose must exist in both files. Every row needs a value in that column, and the same value may appear only once in each file. If not, Opselith stops and tells you what to fix.

What counts as changed?

For rows found in both files, Opselith compares columns with the same name. A value is marked as changed when the text is different.