FAX (facsimile) is a communication method for sending and receiving copies of documents and images to remote locations over phone lines. The sending side scans the original, transmits the image data via phone line, and the receiving side prints it. The G3 method - with transmission procedures defined in ITU-T T.30 and image coding in T.4 - is the norm, and a standard setting takes roughly one minute per A4 page. The variant known as Super G3 runs faster, cutting transmission time further.
Japan is known as a country where FAX remains firmly embedded in business use. Government offices, medical institutions, real estate, and law firms have FAX embedded in their workflows, making rapid elimination difficult. Behind this are Japan-specific factors including handwritten signature transmission, paper-based business practices, and ensuring document originality. During the COVID-19 pandemic, the use of FAX for health center infection reports was criticized, highlighting delays in digitalization.
Internet FAX (cloud FAX) services also became widespread from the 2010s onward. Internet FAX services such as eFax let you send and receive faxes by email, eliminating the need for a FAX machine. Received faxes are saved as PDFs, contributing to paperless operations. FAX communication continues after the PSTN-to-IP migration, but in VoIP environments, voice codecs may not correctly transmit FAX signals, sometimes requiring T.38 protocol (FAX over IP) support. If FAX transmission errors occur frequently, checking whether the line has been converted to IP is the first troubleshooting step. Also review FAX number management in the business phone number guide.
The underlying principle of the fax was devised by Scottish inventor Alexander Bain in 1843; in Japan it was first used commercially for newspaper phototelegraphy in the 1930s, and home fax machines spread in the 1980s. Operationally, fax has security weaknesses - misdialed numbers can send confidential documents to strangers, documents left in the receiving tray can be read by anyone nearby, and the unencrypted transmission can be intercepted - so double-checking numbers before sending and managing received documents are essential.