050 numbers are assigned to IP phone services. Consisting of 050 plus 8 digits, they're not tied to geographic areas. Available anywhere with internet for a few hundred yen monthly, they serve as secondary business numbers or personal side-job lines.
The major limitation: 050 numbers cannot make emergency calls (110/119). Without location data linkage, emergency services can't determine the caller's location. Users relying on 050 as their primary phone need a separate mobile or landline for emergencies.
050 numbers are also a nuisance call source. Easy online acquisition with minimal verification and multi-number accounts enable disposable number abuse by unscrupulous operators. Exercise extra caution with suspicious 050 calls.
Privacy benefits exist: using 050 for marketplace apps or online shop contacts avoids exposing personal mobile numbers. See IP phone spam measures and phone number structure guide.