Watchdog Timer

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What Does Watchdog Timer Mean?

A watchdog timer (WDT) is an embedded timing device that automatically prompts corrective action upon system malfunction detection. If software hangs or is lost, a WDT resets the system microcontroller via a 16-bit counter.


Computers lacking embedded WDTs often require installed WDT expansion cards.

A WDT is also known as a computer operating properly (COP) timer.

Techopedia Explains Watchdog Timer

A WDT enables embedded system self-reliance in two ways:

  • Detects system glitches or errors, including programming errors, software hangs, code crashes or power surges.
  • Resets operating systems and resumes normal program activity via the reset signal embedded in a CPU or specialized microcontroller chip. This reset process is also known as feeding the watchdog, kicking the dog, waking the watchdog or petting the dog.

One WDT may monitor another to ensure saved and completed data tasks within a designated period this cascading of WDT ensures that when a system failure is being monitored by a WDT, that the WDT itself does not hang too.

WDT provides additional features, as follows:

  • Unreliable sandbox code may be tested by a highly complex WDT for system security.
  • If a website does not load normally, a WDT automatically generates Web browser refresh functionality.

WDTs can exist in software, as a separate hardware microprocessor, or as a microcontrolled subprocessor within a CPU or other parts of the chipset.


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Margaret Rouse
Technology Expert
Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.