Uptime Guarantee
Definition
An uptime guarantee is the availability clause in a service level agreement, written as a percentage measured over a calendar month. Three nines, 99.9 per cent, allows about 43 minutes of downtime in a 30-day month. Four nines, 99.99 per cent, allows about 4 minutes. Two nines, 99 per cent, allows more than seven hours, which is why a bare 99 per cent is close to no promise at all. The percentage is only half the clause: the rest defines what counts as unavailable, what is excluded, how it is measured and what you get when it is missed. Scheduled maintenance, problems on your side of the connection, and outages at third parties such as your DNS provider are normally excluded, so the measured figure can be higher than what your visitors actually experienced.
Why It Matters
The number sets your expectation, and the remedy sets its worth. A guarantee usually pays out as a service credit against future invoices, which you must notice and claim yourself, typically within 30 days of the incident and with your own evidence of when it started and ended. On a plan costing 10 pounds a month, a 10 per cent credit for a four-hour outage is one pound — nothing like the value of the enquiries that did not arrive. So read the clause to understand the provider's own tolerance for failure, not as insurance. If a few hours offline would genuinely hurt, the money is better spent on a tested recovery plan than on a higher tier with a better percentage.
How It Works
Find the measurement window first, because a monthly window is far stricter than an annual one: 99.9 per cent per year permits nearly nine hours in a single stretch and still passes. Check the exclusions, especially planned maintenance, which many agreements do not count at all provided notice was given. Check who measures — if availability comes solely from the provider's own instruments, your own uptime monitoring gives you something to argue with. Note the credit table, usually a sliding scale such as 10 per cent of the monthly fee below 99.9 per cent and 25 per cent below 99 per cent. Then note the claim deadline, and record every outage with timestamps as it happens, since a claim filed on the 40th day is worth nothing.
Real-World Example
An agency hosts a client's product catalogue at halden-catalogue.99helpers.site under a paid plan with a 99.9 per cent monthly figure. In February the site is unreachable for 70 minutes, which breaches the allowance of roughly 43 minutes. Their monitor logged the start at 09:12 and the recovery at 10:22, so the claim takes five minutes to write and produces a credit of a few pounds. The useful outcome is not the credit: it is that the agency now knows what 99.9 per cent buys, and has moved the client's DNS TTL down so that a switch to a standby copy takes minutes if it happens again.
Common Mistakes
- ✕Reading 99.9 per cent as effectively never down — it permits about 43 minutes a month, and those minutes can all fall in one afternoon
- ✕Assuming the credit is automatic — most agreements require you to claim in writing within a fixed window or the right lapses
- ✕Comparing an annual guarantee with a monthly one as if they were the same promise, when the annual version allows a single much longer outage
- ✕Relying on the provider's own availability figures without independent monitoring, so you cannot show when the outage began
Related Terms
Uptime SLA Credit
Money a provider owes back when it misses the availability it promised, usually as a percentage of that month's fee. It is the enforcement mechanism behind an availability promise, and you normally have to claim it.
Downtime
Any period in which a site does not do its job for the people trying to use it. That includes a page that loads but is broken, not only a server that refuses to answer.
Uptime Monitoring
An outside service that requests your site on a schedule and tells you when it stops answering correctly. It exists so that you find out about an outage before your visitors have to tell you.
Status Page
A separate page that says whether a service is working and what is being done if it is not. Its whole value comes from being hosted away from the thing it reports on.
Uptime
Uptime is the share of a period during which a site answers requests normally, quoted as a percentage such as 99.9 percent. Its mirror image is downtime, and the difference between two numbers that look almost identical can be hours.
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