You can find out who called you from a phone number for free using several online reverse phone lookup services. Here are some reliable options:

• Truecaller offers a free reverse phone lookup tool where you enter the number and get the caller's identity quickly. It also flags spam numbers based on user reports

• NumLookup provides a completely free service for US numbers with no registration required. It reveals the owner's full name, location, carrier, and sometimes linked social media profiles

• Spy Dialer is a free, fast, and discreet reverse phone lookup that works for mobile phones, landlines, and even unpublished numbers. It uses public data to find owner names and photos

• Whitepages lets you search phone numbers to get the owner's name, address, carrier info, and spam reports for free on landlines and business numbers. Cell phone details may require payment

• Other free tools include IPQualityScore and Lookify.io for basic info like location and carrier, though detailed personal info often requires paid services

For best results, simply enter the phone number into one of these services' search bars to identify who called you without cost or registration in many cases. Keep in mind that full address details or advanced info may require paid subscriptions on some platforms