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Synthetic monitoring for
REST and GraphQL APIs

Catch breaking API changes before your users doImmediate alerts via Email, SMS, Slack, PagerDuty (+ more)

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Trusted by thousands of businesses

Validate API responses with assertions

Test that your API returns the correct data, not just that it responds with 200 OK.

Verify JSON response structure, check specific field values, and validate status codes match your expectations. Catch breaking changes before your users do.

OnlineOrNot's API assertions for validating response data

Test GET, POST, PUT, DELETE requests

Test authenticated endpoints with bearer tokens, API keys, or basic auth. Add custom headers and request bodies for POST, PUT, and PATCH requests.

Verify your GraphQL API only accepts POST requests, or check that your REST API properly rejects unauthenticated requests.

OnlineOrNot supports all HTTP methods and authentication types

Alerts when tests fail

Get instant alerts when your API tests fail via:

Email
SMS
Slack/Discord
Webhooks
Integrations: Incident.io, PagerDuty, Opsgenie, Grafana OnCall, Spike

OnlineOrNot sends alerts via Email, SMS, Slack, Discord, Webhooks, and on-call integrations

Why teams choose OnlineOrNot

Built and supported by a real human who's been running this business for years. No VC-funded pivot risks, no enterprise sales calls required. Just reliable API monitoring that works, backed by someone who actually responds to support emails.

Catch schema changes instantly.: Validate JSON response structure, check specific field values, and verify status codes. Know when a deploy breaks your API contract before customers file tickets.
Test authenticated endpoints.: Full support for bearer tokens, API keys, basic auth, and custom headers. Verify your auth layer works correctly and rejects bad requests.
Monitor from 6 global regions.: Run tests from US East, US West, Europe, India, Australia, or Japan. OnlineOrNot retries from multiple clouds before alerting to reduce false positives.
Instant alerts when tests fail.: Get notified via Slack, PagerDuty, Incident.io, Opsgenie, SMS, or email the moment a test fails.
API & CLI for automation.: Integrate monitoring into your CI/CD pipeline. Create checks programmatically, query status from your terminal, or build custom dashboards.

Trusted by software teams worldwide

OnlineOrNot is built for scale and runs millions of uptime checks every week. Thousands of software teams, including some of the world's leading brands have already made the switch from other uptime monitors.

Uptime Checks last week: 14.1M
Users: 4,994
Detected incidents last week: 1,621

- OnlineOrNot has been absolutely fantastic for my bot, Noti. It completely transformed the way I monitor online services.
  The real-time notifications keep me in the loop about any downtime, allowing me to take immediate action. If you're looking for a reliable way to monitor your project's status, I highly suggest using OnlineOrNot.
  Adam H
  Maker of Noti
- Bet on indie hackers 🚀
  I tried @RozenMD's OnlineOrNot uptime monitoring, and for a few days got notifications of 2min down time.
  I thought that OnlineOrNot was wrong as Uptime Robot wasn't reporting anything.
  Turns out it was the other way around.
  Khaled Bentoumi
  Founder of Data to Page
- We've been using OnlineOrNot and it has been a life saver.
  It, by far, has been one of the most responsive uptime services we've tried and it only gets better and better as time goes on.
  Alex Bowles
  Founder of Casterlabs
- I just set up some site aliveness checks for @Archium_io with @RozenMD's OnlineOrNot.
  Took me less than five minutes and it was completely self-explanatory, not to mention gorgeous. Seriously good experience.
  Great job, Max! 👏👏
  Graham Lea
  Founder of Archium.io
- OnlineOrNot by @RozenMD is all one needs
  It is easy to set up and very reliable. I have been using it for almost an year now.
  Rajat Saxena
  Founder of CourseLit
- I'm using OnlineOrNot to monitor my @cloakist customers' sites, so I can respond quickly if they stop working
  Love it. Super clean interface, very intuitive. Particularly impressed at how it can wait for full page load
  Thanks @RozenMD for making this awesome tool!
  Louis Barclay
  Founder of Cloakist
- OnlineOrNot does the job for me.
  Charles Miller
  Software Architect at Atlassian