Uptime monitoring runs simple external checks (HTTP, ping, TCP port) that answer one question: is it up and responding? Synthetic monitoring runs scripted, often real-browser transactions that simulate a real user journey, log in, search, add to cart, check out, and measure whether the whole flow works and how fast. One tells you the server answered. The other tells you the feature actually works.
People mix these two up constantly, and the confusion costs money. A team buys an uptime monitor, sees green for weeks, then finds out checkout has been silently failing because a third-party payment script broke. The server was up the whole time. The monitor was doing exactly what it was built to do, which was not the thing they needed. Here is how the two approaches differ, what each one catches, and when you actually need both.
What uptime monitoring is
Uptime monitoring is the lightweight, always-on layer. A monitor hits an endpoint on a fixed interval from one or more locations and records whether it got a healthy response. The check is cheap, so you can run it often and from several regions without much cost or setup.
- HTTP checks request a URL and look at the status code, response time, and sometimes a keyword in the body.
- Ping and TCP port checks confirm a host is reachable and a service is listening, without touching the application layer at all.
- SSL and cron checks watch for a certificate about to expire or a scheduled job that failed to phone home on time.
The whole point is coverage and speed. You want to know within seconds when a server stops answering, and you want that signal confirmed so a single flaky network path does not page your on-call at 3am. What uptime monitoring does not do is understand your product. It sees a response, not a working feature.
What synthetic monitoring is
Synthetic monitoring goes a layer deeper. Instead of asking "did the server respond," it runs a script that behaves like a person using your app, then checks that each step along the way did what it was supposed to. Most serious synthetic monitoring drives a real headless browser, so it renders your JavaScript, clicks real buttons, and follows redirects the way a customer's Chrome would.
- Scripted, multi-step transactions. A single check might load the homepage, log in, search for a product, add it to the cart, and reach the payment screen, asserting on each step.
- Real-browser rendering. Because it runs an actual browser, it catches client-side failures that a raw HTTP check never sees: a broken bundle, a JavaScript error, a form that will not submit.
- Performance timing. It measures how long each step takes, so you can catch a login flow that technically works but has crawled to eight seconds.
The trade is cost and upkeep. Real-browser scripts are heavier to run and more brittle to maintain. A redesigned button, a renamed CSS selector, or a new consent modal can break the script, and you end up chasing false alarms caused by your own front-end changes rather than real outages.
Synthetic monitoring vs uptime monitoring: a comparison
Side by side, the split gets clear. These are two tools for two jobs, not competing versions of the same tool.
| Dimension | Uptime monitoring | Synthetic monitoring |
|---|---|---|
| What it tests | Is the endpoint up and responding? | Does a full user journey complete correctly? |
| How it works | HTTP, ping, TCP, SSL checks on an interval | Scripted steps, usually in a real headless browser |
| What it catches | Server down, timeout, bad status code, expired cert | Broken login, failed checkout, client-side JS errors, slow flows |
| Cost and complexity | Low: fast to set up, cheap to run often | Higher: scripts to write, maintain, and debug |
| Best for | Broad, frequent coverage of everything you run | A handful of critical revenue paths |
You will notice these do not overlap much. Uptime monitoring is wide and shallow. Synthetic is narrow and deep. That is why teams that can afford both run both, and point them at different things.
What each one catches that the other misses
This is the crux. Uptime monitoring will happily report all green while your checkout is broken, because a checkout page that throws a client-side error after a failed API call still returns HTTP 200. The server answered. The feature did not work. An HTTP check cannot tell the difference unless you tell it exactly what a broken response looks like.
Synthetic monitoring catches that broken checkout, but it pays for the privilege. It is heavier to run, slower to react, and far more brittle. Every front-end change is a chance for the script to break, and a script that cries wolf gets muted, which is worse than having no script at all. There is also a whole class of failures neither one sees on its own: bad data. Your checkout flow can pass every synthetic check while quietly writing corrupt orders to your database. Synthetic checks watch the user journey, but to catch silent failures in the data moving through your pipelines you need a different kind of monitor entirely.
alertping
Uptime and assertion checks, on every plan
AlertPing runs HTTP, ping, TCP port, SSL, and cron checks plus API checks with assertions, confirmed across three regions, with SMS, email, Slack, and webhook alerts included everywhere.
Where API checks with assertions sit between the two
There is a useful middle ground that a lot of teams overlook. An
API check with assertions
is heavier than a plain uptime check but far lighter than a full browser script. It calls an
endpoint and then inspects the response body: assert the JSON has a status field of
ok, assert the returned price is a number, assert the array of results is not empty.
That catches a large share of "responded but broken" failures without the cost and fragility of driving a real browser. If your login is an API call behind a form, an assertion on the token in the response tells you the auth path works, no headless Chrome required. It will not catch a purely visual or client-side bug the way real-browser synthetic monitoring does, but for most backend logic it gets you most of the value for a fraction of the upkeep.
This is where AlertPing focuses. We do fast, multi-region uptime monitoring and API checks with assertions. We are honest that we do not do full real-browser scripted synthetic transactions or real user monitoring. If your critical path is genuinely a five-step browser flow, a dedicated synthetic tool is the right call. If you want to know your endpoints are up and your APIs are returning correct data, assertion checks cover it without the maintenance tax.
What synthetic monitoring and uptime monitoring cost
The pricing models differ as much as the products do, and that is usually what decides the question in practice. Synthetic monitoring is sold by the big observability platforms on a meter: you pay per test run, per request or per scripted action, so the bill grows every time you speed a check up or add a region. Uptime monitoring is normally sold on a flat plan with unlimited checks.
Here are the published US list rates, checked in August 2026. An average month is 30.44 days, or 43,833 minutes, so one monitor running every minute from one location is 43,833 executions.
| Vendor and check type | Rate | One 1-minute monitor, 1 location |
|---|---|---|
| Datadog API test | Near $5 per 10,000 runs | $21.92/mo |
| Dynatrace HTTP monitor | $1.00 per 1,000 requests | $43.83/mo |
| New Relic synthetic check | $0.005 above the edition allowance | $219.16/mo |
| Datadog browser test | Near $12 per 1,000 runs | $526.00/mo |
| Dynatrace browser monitor | $4.50 per 1,000 actions | $197.25/mo for each action in the script |
| AlertPing uptime check | Flat plan, unlimited checks | Included from $19/mo |
Two things are worth pulling out of that table. New Relic looks expensive at the margin, but its simple ping monitors are exempt from the meter entirely and free on every edition, so plain uptime on New Relic costs nothing. And Dynatrace bills browser work per action rather than per run, which makes shallow checks cheap and deep user journeys expensive. We worked both through in how much Dynatrace costs and in the Datadog vs Dynatrace comparison. The full rate card across all seven vendors, including Checkly and Grafana Cloud, is on our synthetic monitoring tools page.
The practical read: metered synthetic monitoring is priced for a handful of high-value scripted journeys, not for watching fifty URLs every minute. Flat-priced uptime monitoring is the opposite. Most teams that run both end up with a small number of scripted journeys on the platform they already own, and broad, fast uptime coverage on a flat plan, because doing it the other way round gets expensive fast. There is also a real interval limit to know about: Datadog, New Relic and Dynatrace all floor at one minute, so sub-minute detection is not something you can buy from any of them at any price.
Is synthetic monitoring the same as uptime monitoring?
No. Uptime monitoring checks whether a server is up and responding, using simple external checks like HTTP, ping, and TCP. Synthetic monitoring runs scripted, often real-browser transactions that simulate a full user journey and confirm the feature works. Uptime tells you the server answered. Synthetic tells you the actual flow succeeded.
Do I need both synthetic and uptime monitoring?
Often, yes, if you can maintain both. Uptime monitoring gives broad, frequent, cheap coverage of everything you run. Synthetic monitoring gives deep coverage of a few critical revenue paths. Many teams start with uptime plus API checks with assertions, then add real-browser synthetic monitoring for one or two flows, like checkout, where a silent break costs real money. A full synthetic platform like Datadog does the deep part well but bills per test run, which is why we lay out where a flat-priced watchdog fits on the Datadog alternative page.
If you are choosing where to spend first, start with broad uptime and assertion coverage, because it catches the largest share of outages for the least effort. Layer synthetic on top only for the handful of journeys that genuinely justify the upkeep. And keep the two straight in your head when a status page versus uptime monitoring question comes up, because those are yet another distinct pair. There is a third comparison worth knowing too, namely synthetic monitoring versus real user monitoring, which splits scripted checks from what actual visitors experience. If you are still comparing vendors, our roundup of the best uptime monitoring tools walks through the options, and if you are pricing out a heavier synthetic suite, AlertPing can be a simpler, lower-cost alternative for the uptime and assertion half of the job.