Confirm Gmail Address Existence

Google’s gxlu endpoint reveals whether a Gmail address is registered, based on whether the server sets a cookie in response. This is a passive OSINT check — no email is sent. ¹

The check

curl -v "https://mail.google.com/mail/gxlu?email=${USER}@gmail.com"

• Address exists: response includes a Set-Cookie header (historically COMPASS or similar).
• Address does not exist: no cookie is set.

Scripting the check

if curl -sI "https://mail.google.com/mail/gxlu?email=${USER}@gmail.com" | grep -q "Set-Cookie"; then
    echo "EXISTS"
else
    echo "NOT FOUND"
fi

Caveats

• Google may change or deprecate this endpoint at any time.
• Rate limiting applies; aggressive checking will trigger CAPTCHAs or blocks.
• This confirms the account exists, not that it is actively monitored.

Alternative: account recovery flow

Google’s official account recovery page (https://accounts.google.com/signin/v2/usernamerecovery) also leaks existence via different error messages for valid vs. invalid addresses, but requires solving a CAPTCHA after a few attempts.

Sources

• 2021 — Three Gmail OSINT Tips — Nixintel
• reacherhq/check-if-email-exists

Related: curl-jq-web-apis, linux-reconnaissance-commands

Footnotes

1. 2021 — Three Gmail OSINT Tips — Nixintel ↩