Gmail Address Normalization: Collapsing Aliases to Canonical Inboxes

As explained in our Gmail Dot & Plus Addressing Guide, a single Gmail user can write their address in thousands of valid ways ([email protected], [email protected], [email protected]). For developers cleaning mailing lists or preventing duplicate account signups, email normalization reduces aliases back to one canonical string—when and only when doing so is safe.

The Four-Step Canonicalization Rule for Gmail

Apply these transformations only when the domain (lowercased) equals gmail.com or googlemail.com:

1. Lowercase both local-part and domain.
2. Fold `googlemail.com` to `gmail.com`: Both domains map 1-to-1 to the exact same Google account namespace.
3. Strip `+` and everything after it in the local-part: john.smith+newsletter becomes john.smith.
4. Remove all `.` characters from the local-part: john.smith becomes johnsmith.

Result: [email protected] normalizes cleanly to [email protected].

export function normalizeEmail(raw) {
  const [localRaw, domainRaw] = raw.trim().toLowerCase().split('@');
  if (!localRaw || !domainRaw) return raw.trim().toLowerCase();

if (domainRaw === 'gmail.com' || domainRaw === 'googlemail.com') { const withoutTag = localRaw.split('+')[0].replace(/\./g, ''); return ${withoutTag}@gmail.com; } return ${localRaw}@${domainRaw}; } ```

Why You Must Never Strip Dots on Non-Gmail Domains!

Dots being ignored is a Gmail-specific convention, not an internet standard:

• On Microsoft Outlook/Hotmail, Yahoo, Proton Mail, Fastmail, iCloud, and corporate Google Workspace domains, [email protected] and [email protected] can belong to two completely different human beings!
• Even when normalizing Gmail for duplicate detection, always store and send mail to the exact spelling the user typed so their personal +tag inbox filters continue working as intended.

Need to check whether a signup domain belongs to a temporary email service rather than a consumer mailbox? Query our Disposable Email Domain Checker.