Flash call verification
What is Flash call verification?
Flash call verification confirms a phone number by placing a call that hangs up before the recipient can answer — the caller ID itself carries a one-time code as its trailing digits, so the code is read straight from the incoming-call number instead of an SMS. Because the call is never answered, there is no per-message SMS charge, and it typically costs a fraction of a text-based one-time passcode, especially at volume on Android, where an app can read the calling number automatically.
More detail
The calling number rotates per request from a pool the platform controls, and its trailing digits are minted to match the one-time code — the same digit-matching contract an SMS or voice OTP uses, just carried in the caller ID instead of a message body or spoken prompt.
Flash call verification suits Android particularly well, since an app can read an incoming call's number directly in the background without the user opening anything. On iOS, where apps cannot inspect calls in the background, the user instead reads the digits off the phone's recent-calls list and types them in, the same as a manual OTP entry.
Frequently asked
- How is flash call verification different from an SMS OTP?
- Instead of texting a one-time code, flash call verification places a short call that is never answered — the code is the trailing digits of the calling number itself, so there is no per-message SMS charge for the code.
- Does flash call verification work the same on iOS and Android?
- Both platforms support it, but an Android app can read the incoming caller ID automatically in the background, while an iOS app cannot inspect calls in the background, so an iOS user reads the digits from their recent-calls list instead.
See also
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