API monitoring tools: best API monitoring software and REST API uptime checkers compared

Short answer: pick by how your API fails. If it goes down hard, an uptime tool that checks every 30 seconds and confirms from several regions is enough, and AlertPing, UptimeRobot or Better Stack cover it. If it fails softly, returning 200 with a wrong or empty payload, you need response-body assertions, which Checkly, Postman, Datadog and AlertPing all do. If you need full browser flows and traces on top, that is Datadog or Checkly territory and it costs accordingly. The eight tools below are compared on interval, assertions, alerting and real US dollar list prices.

Check an endpoint first ▸

Last updated August 2026 · US dollar list prices

alertping ▸ run check

live

▸ type a domain and run a real-feel check

▸ probes from 3 regions · FRA · IAD · SIN

▸ waiting…▌

If ever goes down, you get:

Alert fired ▸ 2 channels · 6.2 s after first failure

AlertPing app

● DOWN : HTTP timeout confirmed from 3/3 regions (FRA, IAD, SIN). Incident opened.

sms · on-call

AlertPing: DOWN. Confirmed 3/3 regions . First fail: Frankfurt.

the comparison

Eight API monitoring tools, side by side

The column that decides most purchases is the pricing model, not the feature list. Flat-rate tools bill per monitor, so the invoice is the same in a quiet month and a busy one. Run-based tools bill per check execution, which is cheap at low frequency and expensive the moment you want a one-minute interval on a lot of endpoints.

Tool	Fastest interval	Response-body assertions	Pricing model	Entry price (USD)	Best for
AlertPing	30 seconds (Team plan and up), 60 seconds on entry	Yes, keyword and JSON path	Flat per plan	$19/mo (20 monitors), $59/mo for 30-second checks	Teams who want API and website uptime on one predictable bill
Checkly	10 seconds	Yes, plus Playwright browser flows	Per check run, with included quotas	Free Hobby tier, Starter $24/mo billed annually	Engineering teams who want monitoring defined in code
Postman Monitors	1 minute	Yes, full JavaScript test scripts	Per user, plus monitor request quotas	Free tier with 1,000 monitor requests/mo, Solo $9/user/mo	Teams whose API collections already live in Postman
Datadog Synthetics	30 seconds	Yes, plus chained multi-step API tests	Per 10,000 test runs, on top of the platform	From about $5 per 10,000 API test runs, list	Shops already standardized on Datadog
UptimeRobot	30 seconds (Enterprise), 60 seconds on Solo	Keyword matching only, no JSON path	Flat per plan	Solo $10/mo monthly, $9/mo billed annually	Simple up or down checks on a small budget
Better Stack	30 seconds on paid plans, 3 minutes free	Yes, keyword and status assertions	Modular blocks (monitors, seats, heartbeats)	Free (10 monitors), then roughly $25/mo for 50 monitors	Teams who want on-call scheduling in the same product
Site24x7	1 minute on standard plans	Yes, including multi-step API sequences	Base plan plus metered add-ons	Free Forever tier, web uptime from about $10/mo	Teams needing wide protocol and infrastructure coverage
Prometheus + Blackbox Exporter	Whatever you configure	Regex on the response body	Self-hosted, no license cost	Free software, you pay in hosting and time	Kubernetes shops with Prometheus already running

Prices are US dollar list prices checked in August 2026. Vendor sites render prices in the visitor's local currency, so a figure you see from outside the United States may not match these. Where a tool sells annual billing at a discount, the billing basis is stated next to the number, because comparing one vendor's annual rate against another's monthly rate is the easiest way to reach a wrong conclusion.

what you are actually buying

An API can return 200 and still be broken

This is the difference between an API monitoring tool and a website uptime checker pointed at a URL. A website that fails usually fails visibly. An API tends to fail quietly: the endpoint answers, the status code is 200, and the payload is an empty array where there should be orders, a null token where there should be a session, or an error object wrapped in a success envelope by a well-meaning gateway.

Status-only monitoring passes all of those. So the first question to ask about any tool on this page is not how fast it checks, it is what it is allowed to assert on. Keyword matching catches some of it. A JSON path assertion like $.data[0].id catches most of it. Full scripted tests catch the rest and cost the most to maintain.

The practical detail behind each of these layers is in our guide to monitoring an API for errors.

Failure	Status code	Caught by
Server down, connection refused	None	Any uptime checker
Unhandled exception	500	Any uptime checker
Auth expired, redirected to login	200 or 302	Strict status code assertion
Empty result set from a broken query	200	JSON path assertion
Error object inside a success envelope	200	JSON path assertion
Field type changed, number became string	200	Schema or scripted test
Degrading response time before a timeout	200	Response time threshold
Rate limit quietly throttling a partner	429	Strict status code assertion

Roughly half the rows in that table return a 200. That is the case for choosing a tool that reads the payload, and the reason a simple ping-based checker is the wrong instrument for an API even though it is the cheapest one.

buying criteria

Six things to check before you pick API monitoring software

Feature grids look interchangeable at this level. These are the details that decide whether the tool earns its place a year in.

How the bill scales with frequency

Run-based pricing is the one that surprises people. Fifty endpoints checked every minute from three locations is over six million runs a month, and at list rates that is a four-figure invoice. Flat per-monitor pricing costs more at tiny scale and far less once you want frequent checks on real coverage.

Whether it confirms before it pages you

A single failed request from one region is usually a network blip, not an outage. Tools that re-check from a second and third location before alerting cut false pages sharply. Without that, faster intervals mostly buy you more noise, and an on-call engineer who stops trusting the alerts.

Authentication handling

Most useful endpoints sit behind a token. Check whether the tool can store custom headers, whether it can refresh an OAuth token, and what happens when the token expires. A monitor that starts alerting because its own credentials went stale is worse than no monitor.

How alerts actually reach a human

Email is where alerts go to be missed at 2am. Look for SMS and phone escalation, and check whether they are included or sold as credits, because that detail changes the real monthly cost more than the headline price does.

Whether it runs outside your infrastructure

Monitoring that runs inside the cluster it watches goes down with it. That is the honest cost of the free self-hosted options, and it is why teams who start with Blackbox Exporter often end up adding an external check anyway.

Maintenance cost of the checks themselves

Scripted tests are powerful and they rot. Every API change breaks a script, and a suite nobody maintains gets muted. Assertions you can express in one line survive longer than a test file, so match the depth of checking to the time you will genuinely spend on it.

tool by tool

Where each one is genuinely the right answer

AlertPing

Built for teams who want their API endpoints and their marketing site watched by the same tool on one flat invoice. Checks assert on status code, a keyword or a JSON path, and a response time threshold, and every failure is re-tested from Frankfurt, Virginia and Singapore before anyone gets woken up. SMS, email, Slack and webhook alerts are on every plan rather than sold as credits. Pricing is flat: $19 a month for 20 monitors at 60-second checks, $59 for 100 monitors at 30-second checks.

Where it loses: there is no free plan and no scripted multi-step API test, so a login-then-fetch-then-post sequence is out of scope. There is no APM, no distributed tracing and no real user monitoring. If you need to know why an API got slow rather than that it did, buy an observability platform instead.

How our API monitoring works ▸

Checkly

The strongest choice if you want monitoring to live in your repository. Checks are defined in TypeScript and deployed from CI, browser flows use Playwright, and intervals go down to 10 seconds. The free Hobby tier covers 10 uptime monitors with a large API check quota, Starter is $24 a month billed annually for 50 monitors and 25,000 API check runs, and Team is $64 a month billed annually with all global locations and 100,000 API runs.

Where it loses: the monitoring-as-code model that makes it excellent for engineers makes it awkward for anyone else, and there is real setup work before the first check runs. Overages are billed per thousand browser runs and per ten thousand API runs, so a frequent-check setup needs modelling before you commit.

Postman Monitors

If your API collections are already in Postman, this is the shortest path to monitoring that exists: point a monitor at a collection you have already written and it runs on a schedule. Tests are full JavaScript, so assertions can be as deep as you like. The free tier includes 1,000 monitor requests a month per user and Solo is listed at $9 per user per month with 10,000, with Team at $19 and Enterprise at $49 per user per month.

Where it loses: the minimum interval is one minute and monitoring is a feature of an API development platform rather than an alerting product, so incident routing, escalation and status pages are not really there. Per-user pricing also means the bill tracks team size, not monitoring need.

Datadog Synthetics

The most capable option on this page, and the only one where an API alert sits next to the traces, logs and host metrics that explain it. Multi-step API tests can chain calls and pass variables between them, and the same platform covers browser tests and TLS validation. API test runs are priced from around $5 per 10,000 at list, on top of whatever the rest of Datadog costs you.

Where it loses: cost, and the way it arrives. Run based pricing at a one-minute interval across a few dozen endpoints and several locations reaches thousands of dollars a month at list rates. Buying Datadog purely to check whether an API answers is the wrong tool by an order of magnitude.

Datadog alternative, compared honestly ▸

UptimeRobot

The default cheap answer, and for a plain up or down check on a public endpoint it is a reasonable one. Solo is $10 a month billed monthly or $9 billed annually for 10 monitors at 60-second checks, and 30-second checks arrive on the $69 a month Enterprise plan billed annually. The free tier covers 50 monitors at five-minute intervals for non-commercial use.

Where it loses: assertions stop at keyword matching, so the 200-with-a-broken-payload failures in the table above go straight through. SMS is sold as credits rather than included. For a website that is fine. For an API it is the gap that matters most.

UptimeRobot alternative, compared honestly ▸

Better Stack

Formerly Better Uptime, and the pick when the alert matters more than the check. On-call scheduling, escalation policies and log management sit in the same account, so an API failure routes through a real rotation rather than an email list. The free plan covers 10 monitors at three-minute checks, and paid usage starts around $25 a month for 50 monitors.

Where it loses: monitors, responder seats and heartbeat blocks are billed separately, so working out next year's cost takes a spreadsheet. Assertion depth sits below Checkly and Datadog, closer to keyword and status matching than full payload inspection.

Better Stack alternative, compared honestly ▸

Site24x7

Part of the Zoho suite, and the broadest coverage per dollar if you need servers, networks and APIs watched by one vendor. Multi-step API sequences are supported, and there is a Free Forever tier plus web uptime monitoring from around $10 a month. Worth a look when the API is one item on a long infrastructure list.

Where it loses: the base-plan-plus-add-ons model makes the real monthly cost hard to predict, and 30-second polling is reserved for the top enterprise tier. The interface carries the weight of everything it covers.

Site24x7 alternative, compared honestly ▸

Prometheus and Blackbox Exporter (open source)

Free, well understood, and already installed in most Kubernetes clusters. Blackbox Exporter probes HTTP endpoints, checks status codes, matches a regex against the response body and exposes TLS expiry from a real handshake. Pair it with Alertmanager for routing and Grafana for dashboards and you have genuine API monitoring with no license fee.

Where it loses: you own the uptime of your own monitoring, and a regex over a JSON body is a blunt instrument next to a path assertion. There is no SMS escalation without more moving parts. Excellent when the stack already exists, poor when you would be standing it up just to watch a few endpoints.

questions people ask

API monitoring questions

What is API monitoring?

API monitoring is an automated check that calls your endpoints on a schedule from outside your infrastructure and verifies the response, not just that one arrived. A real check asserts on the status code, on values inside the response body, and on response time, then alerts a human when any of the three fails.

What are the best API monitoring tools?

There is no single best one, because the tools split by job. Checkly is best for monitoring defined in code, Postman for collections you have already written, Datadog when you need traces alongside the alert, UptimeRobot for the cheapest simple check, and AlertPing when you want APIs and websites on one flat bill with SMS included.

What is the difference between API monitoring and API testing?

API testing runs before you ship, against a build, to prove new code is correct. API monitoring runs forever afterwards, against production, to prove it still is. The assertions look similar and the purpose is opposite: testing blocks a release, monitoring wakes someone up. Tools like Postman and Checkly deliberately blur the line by reusing the same test definitions for both.

Why is API monitoring important?

Because APIs fail silently and their users are machines that cannot tell you. A broken web page generates support tickets within minutes. A broken payments or auth endpoint generates failed transactions that look like normal traffic in your dashboards until someone reconciles revenue at the end of the week.

Are there free API monitoring tools?

Yes. Checkly has a Hobby tier, Better Stack and Site24x7 have free plans, Postman includes 1,000 monitor requests a month, and Prometheus with Blackbox Exporter is free to self-host. The limits are always interval, volume and escalation: free tiers check slowly, cap the number of endpoints, and almost never include SMS, which is the alert that gets answered at the weekend.

What are open source API monitoring tools?

Prometheus with Blackbox Exporter is the most widely deployed, and Zabbix covers HTTP checks natively. Uptime Kuma is a popular self-hosted option for simple status checks. All three are genuinely capable, and all three share one weakness: they run on infrastructure you also own, so a failure that takes down the host takes the monitoring with it.

What are REST API monitoring tools?

The same tools listed here. REST monitoring means issuing an HTTP request against a resource URL and asserting on the JSON that comes back, which every tool on this page can do. GraphQL needs a tool that can POST a query body, and gRPC or WebSocket endpoints narrow the field considerably, so check protocol support before you buy if you run either.

How do I monitor an API endpoint?

Add the URL with the method and any auth headers it needs, set the expected status code explicitly rather than accepting anything under 400, add one assertion on a field that only exists when the endpoint really worked, set a response time threshold, then route the alert to SMS or Slack. Start with the endpoints that cost money when they fail.

How often should an API be monitored?

You learn about an outage roughly half a check interval after it starts, so a five-minute interval hides about two and a half minutes of downtime on average. Use 30 to 60 seconds on revenue and auth endpoints, and five minutes on internal ones nobody is paged for. The full reasoning is in our guide to how often to check uptime.

Is API Monitor the same as API monitoring software?

No, and the name collision causes real confusion. API Monitor is a Windows desktop utility that traces the Windows API calls a running process makes, used in debugging and malware analysis. The tools on this page monitor web APIs over HTTP from outside your network. Different job, different category, similar search results.

Watch your APIs and your websites with one flat bill

AlertPing checks endpoints as often as every 30 seconds, asserts on status code, JSON path and response time, and confirms every failure from three regions before it alerts you. SMS, email, Slack and webhook on every plan, from $19 a month.

See pricing

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