How to compare two lists and find the differences
Which emails are only in the new export? Which SKUs disappeared? Put one item per line, normalize both lists, and a diff answers it instantly.
The quick method
- Paste the first list into the left box and the second list into the right box, one item per line.
- Open Tools and apply Sort lines A → Z to Both. Sorting puts matching items on the same lines, so the order of the original lists stops mattering.
- Apply Remove duplicate lines to both if repeated items aren't meaningful to you.
- Read the result: lines marked as removed are only in the first list; lines marked as added are only in the second.
Everything runs in your browser, so this is safe for customer emails or internal IDs.
Normalize before comparing
Lists from different systems rarely match character for character. A few normalizations remove false differences:
- Case:
[email protected]and[email protected]are usually the same address. Turn on Ignore → Ignore case, or apply Tools → Lowercase to both. - Spaces: trailing spaces are invisible and common in exports. Use Tools → Trim leading/trailing spaces, or Ignore → Ignore trailing whitespace.
- Blank lines: Tools → Remove blank lines, or Ignore → Ignore blank lines.
- Noise inside items: if items carry timestamps or IDs you don't care about, add a pattern under Ignore → Ignore inside lines so those parts are masked out of the comparison.
Lists with several columns
If each item has several fields (a CSV export with ID, name and price, for example), compare it as a table instead. The CSV comparison matches rows by a key column such as the ID, regardless of order, and tells you which fields changed for each record. For Excel files, use the Excel comparison.
Doing it in a spreadsheet or the command line
In Excel or Google Sheets, =COUNTIF(B:B, A2)=0 next to each item in column A flags items missing from column B. On the command line, comm does the same for sorted files:
sort -u list-a.txt > a.sorted
sort -u list-b.txt > b.sorted
comm -23 a.sorted b.sorted # only in A
comm -13 a.sorted b.sorted # only in BA visual diff shows both directions at once and lets you fix inconsistencies on the spot, which is often quicker for one-off checks.