TL;DR: Both are effective, well-reviewed spam call blockers — RoboKiller's answer-bot feature is a distinctive extra if you want some active pushback against scammers, while Nomorobo is a solid, more straightforward choice with a longer track record.
RoboKiller and Nomorobo are two established robocall and spam call blocking apps that work by screening incoming calls against known spam number databases.
What to Look For
Both apps screen incoming calls in real time against continuously updated spam and scam number databases, and both work across iOS and Android with similar core blocking functionality.
Key Differences
RoboKiller adds a distinctive feature of playing pre-recorded "answer bots" that waste scammers' time on calls that do get through, along with more general spam text filtering. Nomorobo has a longer track record specifically in the call-blocking space and has offered a free tier for landline blocking in addition to its mobile app.
The Bottom Line
Both are effective, well-reviewed spam call blockers — RoboKiller's answer-bot feature is a distinctive extra if you want some active pushback against scammers, while Nomorobo is a solid, more straightforward choice with a longer track record.
If this looks similar to something else you've seen, it's worth reading Signal vs WhatsApp: Which Is More Private?.
This pattern shows up elsewhere too — see YubiKey vs Google Titan: Which Security Key Is Better?.
Frequently Asked Questions
What’s the short answer?
Both are effective, well-reviewed spam call blockers — RoboKiller's answer-bot feature is a distinctive extra if you want some active pushback against scammers, while Nomorobo is a solid, more straightforward choice with a longer track record.
What should I actually look for?
RoboKiller and Nomorobo are two established robocall and spam call blocking apps that work by screening incoming calls against known spam number databases.