Voyage data recorder, or VDR, is a data recording system designed for all vessels required to comply with the IMO's International Convention SOLAS Requirements (IMO Res.A.861(20)) in order to collect data from various sensors on board the vessel. It then digitizes, compresses and stores this information in an externally mounted protective storage unit. The protective storage unit is a tamper-proof unit designed to withstand the extreme shock, impact, pressure and heat, which could be associated with a marine incident (fire, explosion, collision, sinking, etc.).

The protective storage unit may be in a retrievable fixed unit or free float unit (or combined with EPIRB) when the ship sunk in marine incident. The last 12 hours of stored data in the protected unit can be recovered and replayed by the authorities or ship owners for incident investigation. Beside the protective storage unit, the VDR system may consist of recording control unit and data acquisition unit, which connected to various equipment and sensors on board a ship.