Email alias checker
Paste a list of signup emails. We normalize Gmail dots and +tags and show which addresses are secretly the same inbox. Runs in your browser.
Why one inbox can become 50 free trials
Gmail ignores dots in the username and everything after a +. To your signup form, john@gmail.com, j.ohn@gmail.com and john+trial7@gmail.com are three different users. To Gmail they are one inbox, and one person can verify all of them.
The normalization rules we use
- gmail.com and googlemail.com: lowercase, remove dots, drop everything after
+, map googlemail.com to gmail.com. - Other providers: lowercase and drop the
+tag(optional, since some custom mail servers treat+as a real character). - Never rewrite the address you email. Store the raw address and use the normalized one only to detect duplicates.
Deep dive: Gmail dots and plus aliases: how one inbox becomes 50 free trials.
FAQ
Does Gmail really ignore dots?
Yes, for gmail.com and googlemail.com addresses Gmail ignores dots in the username and anything after a plus sign. j.o.h.n+7@gmail.com delivers to john@gmail.com.
Should I normalize all providers the same way?
No. Dots are only ignored by Gmail. Plus addressing is supported by many providers (Outlook, iCloud, Fastmail, Proton), but some company mail servers treat + as a real character. Normalize for duplicate detection, but always keep the raw address the user typed.
Is my list uploaded anywhere?
No. This tool runs entirely in your browser. Nothing you paste leaves the page.
Catch these signups automatically.
One API call at signup. Starts in monitor mode, so nothing breaks.