Okurinbou is a free file transfer service from Bit Park Inc. with a long track record of operation in Japan. The service holds ISO 27001 (ISMS) certification, giving it security credibility that is uncommon among free, ad-supported transfer services.

Unregistered users can send files immediately, while free member registration raises the size limit and adds email notifications for uploads and downloads. A separate corporate version called Okurinbou BIZ provides multiple accounts and additional management features for business teams.