Compare two email lists

Paste two email lists to see which addresses are in both, only in the first, or only in the second — with case-insensitive matching and duplicate detection.

Open this example in List Comparator

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

Open this example in List Comparator →

The problem

You have two lists of email addresses — say subscribers and customers — and need the overlap, the unique entries on each side, and any duplicates. Doing it by hand is slow and misses case differences. A set comparison gives you the answer instantly.

Sample input

List A
ada@example.com
ben@example.com
cleo@example.com
List B
Ben@example.com
cleo@example.com
dan@example.com

Expected output

Result (case-insensitive)
In both:      ben@example.com, cleo@example.com
Only in A:    ada@example.com
Only in B:    dan@example.com

Ben@example.com and ben@example.com match because the comparison is case-insensitive.

How to do it

  1. Paste the first email list.
  2. Paste the second email list.
  3. Choose case-insensitive matching.
  4. Compare the lists.
  5. Copy the in-both, only-in-A, or only-in-B set you need.

Common mistakes

  • Case-sensitive comparison treating Ben@ and ben@ as different.
  • Leading or trailing spaces around addresses.
  • Duplicates within one list inflating the counts.
  • Mixing names and emails in the same list.
  • Different separators, such as commas versus newlines.

Related tools

Related guides

FAQ

How do I find emails in both lists?

Paste both lists and compare. The in-both set contains every address that appears in each list, matched case-insensitively if you choose that option.

Is the comparison case-insensitive?

It can be. Enable case-insensitive matching so Ben@example.com and ben@example.com are treated as the same address.

Does it remove duplicates within a list?

Yes. Duplicates inside a single list are collapsed so they do not distort the in-both or only-in counts.

Can I compare more than emails?

Yes. The list comparator works on any line-separated values, such as IDs, SKUs, or usernames.

Are my lists uploaded?

No. The comparison runs locally in your browser. Neither list is sent to a server.

List comparison runs locally in your browser. Your lists are not uploaded.

Explore more data cleanup and QA tools

Compare lists, diff CSVs, clean data and build SQL filters — grouped in one place.

View the data cleanup & QA toolkit →

Practical example and expected result

Paste two email lists to see which addresses are in both, only in the first, or only in the second - with case-insensitive matching and duplicate detection. In practice, this is most useful when you need a quick, repeatable check on a developer artifact before adding it to a ticket, pull request, test fixture, or support note.

A realistic input for this workflow is ada@example.com ben@example.com cleo@example.com. The expected result should resemble Ben@example.com cleo@example.com dan@example.com, with the same important values preserved.

Troubleshooting checklist

  • Confirm you copied the complete developer artifact and not only a partial line or truncated preview.
  • Run the local tool once with a safe sample, then repeat with the real data only if your team policy allows it.
  • Check quoting, escaping, whitespace, encoding, timestamps, and environment-specific values before trusting the result.
  • Before sharing output, remove secrets, tokens, cookies, customer data, and production hostnames that are not needed for the review.

Next useful steps

Review checklist before sharing the result

For Compare two email lists, the safest workflow is to test with a small sample, confirm the output shape, then repeat with the real artifact only when needed. Keep the original input open until you verify that no value was dropped, decoded twice, sorted unexpectedly, or changed from text into a different type.

Before copying the result into a pull request, issue, chat thread, or support ticket, scan for private values. Replace real IDs, bearer tokens, session cookies, email addresses, internal hostnames, and customer data with placeholders. If another tool is listed above, use it as the second pass rather than manually editing complex output.

  • Keep one line of context explaining why the transformation was needed.
  • Preserve enough sample structure for a reviewer to reproduce the result locally.
  • Note any assumptions about encoding, timezone, delimiter, schema version, or runtime environment.