Sprawdź Kto Dzwonił is a Polish online service that helps people identify unknown callers and make informed decisions before answering or returning a call. Its free, searchable database covers mobile, landline and premium-rate phone numbers, with information gathered from user reports, community comments and analysis of calling patterns. Visitors can enter a number in different formats, including with Poland’s +48 prefix, and view available community verdicts, categories and descriptions without registering.

Users can also submit reports, classify numbers and share details of calls, helping warn others about suspected scams, telemarketing, automated calls, debt collection and other unwanted contact. Reports are moderated, and the service highlights recently reported and searched numbers, popular categories and monthly rankings. The site also provides guidance on recognizing telephone fraud, responding safely to suspicious calls and protecting personal and banking information. Its educational articles cover phone security and call management, while additional features include information about phone prefixes, a quiz and contact options.