Both glitches and hazards seem to be very similar. Can the difference be explained with the help of an example?

  • 2
    \$\begingroup\$ Hazards are the potential in a design to create glitches. \$\endgroup\$ Jul 12 at 21:12
  • 1
    \$\begingroup\$ Same as the difference between accident and accident-prone. \$\endgroup\$
    – Mitu Raj
    Jul 16 at 8:53
  • \$\begingroup\$ In digital logic, a hazard in a system is an undesirable effect caused by either a deficiency in the system or external influences. ... This results in the logic not performing its function properly. The three different most common kinds of hazards are usually referred to as static, dynamic and function hazards. \$\endgroup\$
    – Gil
    Jul 17 at 1:37
  • \$\begingroup\$ As far as I know glitches are short spikes and hazards are circuit deficiencies which cause this... But many a time, the terms are used interchangeably. Why is it so? \$\endgroup\$ Jul 17 at 6:07

In Digital electronics, a hazard is a glitch waiting to happen. For example, static and dynamic hazards in digital logic.

A hazard is a possibility, while a glitch is the event.

A glitch is an undesirable output, which might be for a short duration. For example, glitches are likely to be present on the non-registered outputs of Mealy Finite State Machines. Registering the outputs (i.e. adding a register at the output) reduces the likelihood of a glitch.

As an analogy, you might have heard of "choking hazard" - the hazard of choking. Choking is the event, and choking hazard is the possibility of choking.

Can glitch and hazard be used interchangeably?

No, glitch and hazard cannot be used interchangeably. For example, we say a glitch has occured, we never say a hazard has occured. We say a hazard exists, and this means that we know for sure that a glitch will occur under certain conditions, and we know what those conditions are.


I don't think the word "glitch" has any standardized meaning. You have to see how it is used in the context of whatever you are studying to see how that author uses the word.

  • \$\begingroup\$ There is a somewhat "standard" name for a specific cyber attack "glitch attack". \$\endgroup\$
    – Eugene Sh.
    Jul 12 at 20:22
  • \$\begingroup\$ I was talking only in the context of "digital logic" since that was the OP's tag. \$\endgroup\$ Jul 12 at 21:01
  • \$\begingroup\$ While I've definitely heard and used "glitch" in reference to digital logic, I have not heard or used "hazard." Although if a glitch were big or long enough, it could be considered a hazard - but I wouldn't call it that. Likely a "big glitch" or similar. \$\endgroup\$
    – rdtsc
    Jul 12 at 21:05
  • \$\begingroup\$ My interpretation is a glitch is an unwanted timing anomaly whereas a hazard is a sequence that has a undesired effect - eg both sides of a dual port ram writing to the same location. Definitely not a glitch but something you'd want to avoid. Hazard is normally used to describe a situation in a pipelined processor where certain sequences might cause an add to occur before a move on a given register or suchlike due to the order of operations in the pipe. \$\endgroup\$
    – Kartman
    Jul 12 at 22:20
  • \$\begingroup\$ "We fixed the glitch" - Office Space. \$\endgroup\$ Jul 12 at 22:39

"Glitch" is something of a moveable feast. Basically, it refers to a system behaving in an unexpected way.

At the lowest level, looking at a single signal, a glitch would be a pulse which appears where there shouldn't be one. Or, the signal changes polarity when it shouldn't.

At higher levels of abstraction, this can generally be described as a sudden, unexpected or inappropriate change in the variable being observed. A system which measures pressure in a vessel, for instance, which suddenly reports that the pressure has doubled, and then reverts to the original pressure, would be said to have experienced a glitch. Or, if a finite state machine controls a traffic light (and that was an early use of digital tech), and the light changes from green to red without an apparent yellow in between, that would be a glitch in the FSM operation, especially if it never happened again.

A hazard, in this sort of situation, is an identified condition which might produce a glitch. An example in the case of the traffic light FSM might be the realization that transitions in the internal states violate setup or hold times of the flip-flops. There are various types of hazards, and in complex systems some of them can be difficult to detect beforehand.

And Murphy's Law applies rigorously, one subsection specifying that some hazards will not manifest themselves during testing.


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