How NoCall works on iPhone: CallKit, offline identification and SMS filter
Apple does not let apps read your calls. Instead, iOS offers a Call Blocking & Identification extension (part of CallKit): an app gives the iPhone a list of numbers, and the phone itself uses that list when a call comes in. NoCall is built on that system.
How call identification works on iPhone
The NoCall app downloads the community spam database and hands it to iOS through its extension. When a call arrives, the iPhone compares the number with that list on the device. NoCall never sees the call and the number is not sent anywhere to be checked.
Because the list is stored on the phone, identification also works without mobile data or Wi-Fi.
How to turn it on
- Install NoCall from the App Store, open it and sign in.
- Sync the spam database from the app.
- Open Settings › Apps › Phone › Call Blocking & Identification.
- Turn on NoCall.
On older versions of iOS the option is under Settings › Phone › Call Blocking & Identification.
Identify or block: Free and Pro
- Free: Known spam numbers are identified: the incoming-call screen shows a NoCall label, and you decide whether to answer.
- Pro: You can turn on automatic blocking so that known spam calls are blocked silently instead of ringing.
SMS filter
NoCall also includes an iOS SMS filter. It decides on the iPhone where a text from an unknown sender should go, and texts from numbers in the spam database can be moved to the Junk folder. Message content never leaves the device. Pro adds extra filtering rules.
- Open Settings › Apps › Messages › Unknown & Spam.
- Under SMS Filtering, choose NoCall.
Keeping the list fresh
New reports reach your iPhone when the database syncs. On Free you sync manually from the app; Pro can sync daily, weekly or automatically in the background, with an optional Wi-Fi-only setting.
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