Data logging is the practice of recording, in some medium, sequential input, often in a time-associated format.

The earliest kind of data logging is that of the old sailing vessels, where the captains kept their log. This is where the term logging derives. The captain would typically make at least a daily entry recording the date, time, weather, sea conditions, bearing, estimated speed, and any noteworthy events.

Now any time-sequential record of events or conditions is called a log.

See also web log.