Numverify
Phone number validation and carrier lookup API for developers
...Developers use it to clean signup forms, filter fake accounts, reduce wasted SMS spend, and enrich customer records with carrier and line type data. The API returns clean JSON, works with any language that can open a URL, and includes code samples for Python, PHP, JavaScript, and more.
Key features include real time validation, carrier detection, line type detection for mobile, landline, and VoIP numbers, E.164 formatting, and a free tier for testing.
Documentation: https://numverify.com/
Verification guide: https://numverify.com/verifying-phone-number