Uptime monitoring vs synthetic monitoring: what each one catches
Uptime monitoring asks your server whether it is responding. Synthetic monitoring drives a real browser through a journey and confirms the result. They catch different failures, and the gap between them is where most lost revenue sits. This page explains the difference and when you need each.
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What does an uptime check actually test?
An uptime check sends a request to a URL on a schedule and looks at what comes back: did it respond, how fast, and was the status code in the range you expected. Some can also check that a string appears in the response body.
That makes it excellent at one job: telling you the site is down. If the server is unreachable, the certificate expired, or the whole application is throwing errors, an uptime check notices in seconds and it is the cheapest way to know.
What it cannot see is anything that happens after the page arrives. It does not run JavaScript, it does not click, and it has no opinion about whether the page is usable.
What does a synthetic check add?
A synthetic check opens the page in a real browser, performs the steps a customer would perform, and asserts the outcome. It runs the JavaScript, waits for the page to settle, clicks the button, and confirms what appeared afterwards.
That closes the gap the uptime check leaves. A store whose add-to-cart button has stopped responding returns a completely normal response on every page. A signup form that silently rejects submissions returns 200. A checkout link that started erroring after a theme update still serves a page. Every one of those passes an uptime check and fails a synthetic one.
Which failures does each one catch?
| Failure | Uptime check | Synthetic check |
|---|---|---|
| Server down or unreachable | Catches it | Catches it |
| Certificate expired | Catches it | Catches it |
| Whole application erroring | Catches it | Catches it |
| Add-to-cart button stopped working | Misses it | Catches it |
| Checkout link errors after a theme update | Misses it | Catches it |
| Form submits but nothing happens | Misses it | Catches it |
| Third-party script blocking a button | Misses it | Catches it |
| Price or stock message changed | Misses it | Catches it with change monitoring |
| Outage in one country only | Catches it if checked from there | Misses it, one location only |
Do you need both?
Often, yes, and they cost different amounts for a reason.
Uptime checks are cheap because they are cheap to run: one request, no browser. Run them broadly, across every host you care about, and let them tell you when something is properly down.
Synthetic checks cost more because each one drives a real browser. Run them narrowly, on the handful of journeys that cost you money when they break. Two to four per site is usually the right number.
The mistake worth avoiding is assuming the cheap one covers the expensive one's job. It does not, and the failures it misses are the expensive kind: quiet, and specifically on the path to paying you.
Where does Simrix Monitor sit?
Simrix Monitor is synthetic monitoring, built so that the person who needs the alert does not have to be an engineer. Checks drive a real Chromium browser, you build them from templates rather than code, and every alert carries a screenshot of the moment it broke and a plain-English summary.
It is not an uptime tool and does not try to be. Checks run from one location, there is no uptime percentage, no SLA reporting and no status page to publish. If you want broad availability monitoring across regions, run an uptime tool alongside it.
What does Simrix Monitor cost?
| Plan | Monitors | Fastest check | Sites | Per month |
|---|---|---|---|---|
| Free | 2 | 6 hr | 1 | Free |
| Starter | 10 | 30 min | 3 | $49 |
| Growth | 50 | 15 min | 10 | $149 |
| Pro | 150 | 5 min | 25 | $349 |
| Agency | 500 | 1 min | 75 | Talk to us |
Annual billing is 2 months free. See full pricing or start a 14-day free trial, no card required.
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Frequently asked questions
Is synthetic monitoring the same as end-to-end testing?
The mechanics overlap, but the purpose differs. Testing runs a suite against a build before release. Synthetic monitoring watches a small number of journeys continuously in production and tells you when one stops working.
Can synthetic monitoring replace uptime monitoring?
Not fully. An uptime check is cheaper, can run against every host you own, and is better at telling you the whole site is down. Synthetic checks are better at telling you one thing inside a working site has broken.
How often should a synthetic check run?
As often as the cost of not knowing justifies. A checkout on a busy store is worth checking every few minutes; a contact form on a brochure site is fine a few times a day.
Does Simrix Monitor check from more than one region?
No. Checks run from a single location, so it cannot tell you a site is reachable from one country and not another. An uptime tool with regional checks covers that.
What do I get when a synthetic check fails?
With Simrix Monitor, an email carrying a screenshot of the page at the moment of failure and a plain-English summary of what went wrong. Opening the check shows the journey it ran, how far it got, the final URL, the response code and the duration.
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