DELAY is an audio effect which records an input signal to an audio storage medium, and they plays it back after a period of time. The delayed signal may either be played back multiple times, or played back into the recording again, to create the sound of a repeating, decaying echo. The availability of inexpensive digital signal processing electronics in the late 1970s and 1980s led to the development of the first digital delay effects. Initially, they were only available in expensive rack mounted units but eventually as costs came down and the electronics grew smaller, they became available in the form of foot pedals. The first digital delay offered in a pedal was the Boss DD-2 in 1984.

Rack mounted delay units evolved into digital reverb units and on to digital multi-effects units capable of more sophisticated effects than pure delay, such as reverb and Audio timescale-pitch modification effects.
Digital delay systems function by sampling the input signal through an analog-to-digital converter, after which the signal is passed through a series of digital signal processors that record it into a storage buffer, and then play back the stored audio based on parameters set by the user. The delayed ("wet") output may be mixed with the unmodified ("dry") signal after, or before, it is sent to a digital-to-analog converter for output. Many modern digital delays present an extensive array of options, including a control over the time before playback of the delayed signal. Most also allow the user to select the overall level of the processed signal in relation to the unmodified one, or the level at which the delayed signal is fed back into the buffer, to be repeated again. Some systems today allow more exotic controls, such as the ability to add an audio filter, or to play back the buffer's contents in reverse.Digital pedals remain the most popular delay effects for electric guitarists today because of their ease of maintenance, durability, and relatively low cost. As digital memory has become cheaper, modern units have been able to offer rapidly increasing amounts of storage, some as large as the 16-second delay and looping machine offered by Electro-Harmonix.