Glossary · Reliability metrics
Mean time to detect
MTTD, mean time to detect, is the average time between the start of a failure and the moment it is detected, by monitoring or by someone reporting it.
Detection is often the largest part of an incident, and the part nobody sees. Without monitoring, MTTD is the time until a customer complains, which can be hours for a page that isn’t used much at night.
For external checks, detection time is set by the check interval plus any confirmation. An outage is noticed at the next check, on average half an interval after it starts, and confirmed seconds later.
Partial failures take longer to detect: a broken checkout, an error page served with 200, or responses that are slow but successful. Content checks, multi-step flows and response time limits shorten MTTD for those.
MTTD = total time from failure to detection ÷ number of incidents
Example: Three outages detected after 2, 1 and 9 minutes: (2 + 1 + 9) ÷ 3 = 4 minutes.
Uptimecheck checks as often as every minute and repeats a failed check 10 seconds later before it opens an incident, so with a 1-minute interval you typically hear about an outage within a minute or two. Each incident records when the first check failed and when the failure was confirmed; the app doesn’t show MTTD as a separate number.
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Guides 6 min read
MTTR, MTTA and MTBF measure how fast you fix incidents, how fast you respond and how often things break. Formulas, a worked example and practical ways to improve each one.
ReadGuides 7 min read
False alerts teach teams to ignore monitoring. How to cut the noise: confirm every failure with a second check, set sensible timeouts, validate the right URL and route alerts to the people who can act.
ReadAn outage is noticed at the next check, so on average half an interval after it starts. Checking every minute instead of every 5 minutes cuts the average detection time by about 2 minutes.
Single failures happen on healthy services: a dropped packet, a restart. Confirming with a second check adds seconds to detection and removes most false alarms.
Yes, when MTTR is measured from the start of the failure. Faster detection shortens MTTR by the same amount.
Set up your first monitor in under a minute, or look around the live demo first.
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