How to Find Which Email Addresses Are on Several of Your Lists

To find which email addresses are on several of your lists, put every list in one place, tag each address with its source, and count how many sources hold it. The email list overlap checker does that for up to six pasted or uploaded lists, shows how many addresses each pair shares, who is on every list or only one, and gives one merged, deduplicated list with the lists each address came from.

Matching ignores capital letters and, optionally, Gmail dots and +tags.

Why overlap matters before a send

An address on two lists gets the same campaign twice if each list is sent separately, which can raise unsubscribes and spam complaints. It also costs twice: most email platforms bill per contact and most verifiers per address checked. Merge first, verify once.

The by-hand way

1. Paste each list into one sheet and add a column with the list name.
2. Lower-case every address so capitals do not hide matches.
3. Count each address with a pivot table or COUNTIF.
4. Filter for counts of two or more, then separate by list name to see which pairs overlap.

That is workable for two lists. With three or more you need a count for every pair, which is slow in a sheet. For two lists only, see compare two email lists.

Step 1: add the lists

Paste each list into its own box or upload a CSV or TXT file per list, and name the lists. Add boxes up to six.

Step 2: choose the matching rule

Leave "Treat Gmail dots and +tags as the same inbox" on unless you need exact spellings.

Step 3: compare and download

Press Compare the lists. Each cell of the table is the number of addresses two lists share, and the diagonal is each list's own unique count. Download the merged deduplicated list, the addresses on two or more lists, or the ones on every list.

To stack several exports into one file with all their columns, use CSV merge. To remove repeats inside one list, use remove duplicate emails.

What this check cannot do

• The merged download holds the address, how many lists it is on and their names, not your other columns.
• It matches text, so the same person with two different addresses is not found.
• Each list is limited to a 25 MB file.
• It says nothing about whether any address is deliverable.

For the +tag side of the matching rule, see where a plus address is delivered.

Before you send

Once the lists are merged you have one set of unique addresses, and that set still holds closed mailboxes. That is what the verify page is for, with 100 free checks after a Google sign-in. Results are valid, risky or invalid, each with a reason, and the people on your list are never contacted. Pricing lists the options for bigger files.

Try it now

Paste your lists into the email list overlap checker.