LoTW

LoTW, or Logbook of The World, is an online QSL repository and verification service for amateur radio operated by the American Radio Relay League (ARRL). It enables licensed operators to verify contacts for ARRL awards by uploading signed logs. The service uses digital certificates to authenticate log data, helping ensure the integrity of confirmations across the global amateur radio community.

How it works: Operators install the Trusted QSL (TQSL) software to generate a personal digital certificate tied to their callsign. They sign their log files (ADIF) with that certificate and upload them to LoTW. The system cross-matches QSOs reported by both stations; a QSO becomes confirmed when both sides have uploaded matching records. Confirmed QSOs count toward awards such as DXCC, Worked All States, and VUCC.

LoTW maintains a database of valid QSOs, supports many bands and modes, and provides tools for searching and tracking confirmations. The use of PKI-based signatures is intended to prevent spoofing by ensuring that only logs signed with a valid certificate are accepted. The service thereby standardizes and simplifies the verification process for many ARRL awards.

Launched by ARRL in 2009, LoTW has become one of the primary means of obtaining ARRL awards and complements other systems such as paper QSLs or eQSL. Access is free to registered users who obtain a LoTW certificate.

Limitations include that a QSO is only confirmed if both stations have uploaded matching records, and there can be delays while logs are processed. LoTW does not replace personal privacy considerations or the card-based traditions associated with QSLing; it provides a digital record of verified contacts for awards.