Your website might look fine from the outside.
But beneath the surface, your API is struggling. Response times are creeping up. Authentication is silently failing. That critical payment endpoint just started returning 500 errors.
Your users know before you do. And by the time you find out, the damage is done — failed transactions, frustrated customers, and a support inbox on fire.
API monitoring isn't optional anymore. It's the heartbeat of your application.
In this guide, you'll learn everything about API uptime monitoring and health checks: why they matter, what to monitor, and how to set up alerts that catch problems before your customers do.
Why API Monitoring Is Different From Website Monitoring
Website monitoring checks if a page loads. API monitoring goes deeper.
When you monitor a website, you're essentially asking: "Does this URL return a 200 OK and some HTML?" That's valuable — but it only scratches the surface.
APIs are different because:
APIs power everything behind the scenes
Modern applications are API-first. Your mobile app, third-party integrations, webhooks, and even your own frontend all depend on API endpoints working correctly. One broken endpoint can cascade into dozens of failures.
APIs fail in subtle ways
A website either loads or it doesn't. APIs can fail in nuanced ways:
- Returns 200 OK but with an error message in the body
- Works for GET requests but fails on POST
- Responds correctly to some requests but times out under load
- Returns stale cached data instead of fresh results
- Authentication works for some users but not others
APIs are invisible to users (until they break)
When your marketing site goes down, you see it immediately. When your /api/v1/orders endpoint starts timing out, you might not notice until orders stop coming in.
The Real Cost of API Downtime
API failures aren't just technical problems — they're business problems.
| Failure Type | Business Impact |
|---|---|
| Payment API down | Every failed transaction is lost revenue |
| Authentication API slow | Users can't log in, churn increases |
| Webhook endpoint failing | Third-party integrations break silently |
| Mobile API timing out | App store ratings tank overnight |
| Partner API errors | B2B contracts at risk |
A 2023 study found that the average cost of API downtime for businesses is $5,600 per minute. For companies with high transaction volumes, it's significantly more.
But the hidden cost is often worse: lost trust. When your API fails, developers building on your platform lose confidence. That's much harder to recover from than a temporary outage.
What to Monitor in Your API
Effective API monitoring goes beyond "is it up?" Here's what you should track:
1. Availability (uptime)
The baseline: does your API respond at all? This catches:
- Complete outages
- Network failures
- DNS issues
- SSL certificate problems
2. Response time (latency)
How fast does your API respond? Slow APIs cause:
- Mobile app timeouts
- Poor user experience
- Cascading failures in dependent systems
- Failed webhook deliveries
Track percentiles, not just averages. A 200ms average might hide the fact that 5% of requests take 3+ seconds.
3. HTTP status codes
Your API should return the correct status codes:
- 2xx: Success
- 4xx: Client errors (often fine, but watch for spikes)
- 5xx: Server errors (always investigate)
A sudden spike in 500 errors is an early warning of problems.
4. Response body validation
Sometimes APIs return 200 OK but with an error in the body:
{
"status": "error",
"message": "Database connection failed"
}
Your monitoring should validate that the response contains expected content, not just a successful status code.
5. Authentication and authorization
APIs often require authentication. Monitor:
- Do authenticated requests succeed?
- Are tokens being validated correctly?
- Does rate limiting work as expected?
6. Individual endpoints, not just the root
Don't just monitor api.example.com. Monitor the endpoints that matter:
/api/v1/auth/login/api/v1/payments/process/api/v1/orders/api/v1/users/profile
Each endpoint can fail independently. A healthy root doesn't mean healthy endpoints.
The Health Check Endpoint Pattern
The most reliable way to monitor an API is with a dedicated health check endpoint.
What is a health check endpoint?
A health check endpoint is a special URL (typically /health or /healthz) that returns the current status of your service. Unlike regular endpoints, it's designed specifically for monitoring.
A basic health check
At minimum, a health check confirms your service is running:
GET /health
{
"status": "healthy",
"timestamp": "2025-12-25T10:30:00Z"
}
This catches basic failures like crashed processes or unreachable servers.
A comprehensive health check
Better health checks verify dependencies too:
GET /health
{
"status": "healthy",
"timestamp": "2025-12-25T10:30:00Z",
"version": "2.4.1",
"checks": {
"database": {
"status": "healthy",
"latency_ms": 12
},
"redis": {
"status": "healthy",
"latency_ms": 3
},
"external_payment_api": {
"status": "healthy",
"latency_ms": 145
}
}
}
This reveals not just whether your service is running, but whether it can actually serve requests.
Health check best practices
Keep it fast. Health checks should respond in under 100ms. Don't run heavy database queries or call slow external services synchronously.
Check real dependencies. If your app needs a database to work, verify the database connection. A "healthy" status when the database is down is worse than no health check at all.
Include version information. This helps verify deployments and debug issues.
Use appropriate HTTP status codes. Return 200 for healthy, 503 for unhealthy. Don't return 200 with "status": "unhealthy" in the body.
Don't require authentication. Health checks are often called by load balancers and monitoring tools that shouldn't need API keys.
Setting Up API Monitoring That Works
Here's a practical approach to API monitoring:
1. Start with critical endpoints
Don't try to monitor everything at once. Identify your most critical endpoints:
- Authentication
- Core business logic (orders, payments, bookings)
- Data retrieval that powers your UI
- Webhooks and integrations
Monitor these first with 1-minute intervals.
2. Set realistic thresholds
Base your alerting thresholds on actual performance, not aspirational goals:
| Metric | Warning | Critical |
|---|---|---|
| Response time | > 2x baseline | > 5x baseline |
| Error rate | > 1% | > 5% |
| Uptime | < 99.9% (30 day) | < 99% (30 day) |
If your API normally responds in 200ms, alert at 400ms (warning) and 1000ms (critical).
3. Monitor from multiple regions
An API that works from your office might be slow from Tokyo or unreachable from Sydney. Use multi-region monitoring to catch:
- Regional network issues
- CDN configuration problems
- Latency that only affects certain users
- DNS propagation issues
4. Validate response content
Don't trust status codes alone. Configure your monitors to:
- Check for specific text in responses
- Validate JSON structure
- Verify critical fields are present
A 200 OK with "error": "timeout" in the body isn't success.
5. Alert the right people
Route alerts based on severity and ownership:
- Critical payment API failure → SMS to on-call engineer
- Elevated latency on internal API → Slack notification to team
- Minor degradation → Email summary
Avoid alert fatigue by not sending SMS for every warning.
Common API Monitoring Mistakes
Monitoring only the homepage
"Our website works, so everything's fine." Meanwhile, /api/checkout has been returning 500s for an hour.
Fix: Monitor individual endpoints, especially those that handle critical flows.
Ignoring latency until it's a crisis
Response time creeping from 200ms to 800ms over a month isn't dramatic — until your mobile app starts timing out.
Fix: Set latency thresholds and alert on degradation, not just outages.
Not testing authenticated endpoints
Your public endpoints work fine. But the endpoints that require authentication? Nobody's monitoring those.
Fix: Configure monitors with auth headers or tokens. Many monitoring tools support this.
One check every 5 minutes
Five minutes is an eternity during an outage. If your checkout API fails for 4 minutes before you know, that's a lot of abandoned carts.
Fix: Use 1-minute intervals for critical endpoints. Reserve 5-minute intervals for less critical monitoring.
Trusting the status page of dependencies
Stripe, AWS, and Twilio all have status pages. But their "all systems operational" doesn't mean your specific integration is working.
Fix: Monitor your integration with third-party services, not just their public status.
API Monitoring Checklist
Use this checklist when setting up monitoring for your API:
- Health check endpoint exists and verifies dependencies
- Critical endpoints are monitored individually
- Response time thresholds are set based on baseline performance
- Response body validation is configured for key endpoints
- Multi-region monitoring is enabled
- Authenticated endpoints are covered
- Alert escalation is configured (email → SMS → phone)
- Runbooks exist for common failure scenarios
- Status page reflects API health for customers
How Webalert Monitors Your APIs
Webalert is built for exactly this kind of monitoring:
See the full feature list and compare plans on pricing.
HTTP/HTTPS endpoint monitoring
Monitor any URL with custom headers, authentication, and request methods. Configure expected status codes and response validation.
1-minute check intervals
Catch problems fast with 1-minute intervals on paid plans. Don't wait 5 minutes to learn your payment API is down.
Multi-region checks
Monitor from US, EU, and APAC regions. Catch issues that only affect certain geographic locations.
Response body validation
Verify that responses contain expected content. Catch those sneaky 200 OK responses with error bodies.
Custom headers and authentication
Add API keys, Bearer tokens, or custom headers to your requests. Monitor authenticated endpoints like your users experience them.
Instant alerts
Get notified via email, SMS, Slack, or webhooks the moment something fails. Route critical alerts to on-call engineers.
Response time tracking
Track latency over time. Spot degradation trends before they become outages.
Quick API Health Check
Ask yourself:
- Do you monitor more than just your website homepage?
- Do you have a dedicated
/healthendpoint? - Are critical endpoints monitored individually?
- Would you know within 1 minute if your payment API failed?
- Are authenticated endpoints being monitored?
- Do you monitor from multiple geographic regions?
If you hesitated on any of these, there's a gap in your API monitoring.
Final Thoughts
Your API is the backbone of your application. Every mobile app session, every third-party integration, every webhook depends on it working correctly.
Yet most teams monitor their websites religiously while leaving APIs as an afterthought. They find out about API failures from users, from partners, or from revenue dashboards that suddenly drop.
It doesn't have to be this way.
With proper API monitoring — dedicated health checks, individual endpoint coverage, response validation, and fast alerting — you can catch problems before they cascade. You'll know about issues in minutes, not hours. You'll fix things before customers even notice.
Your API is too important to leave unmonitored.
Ready to monitor your API like it matters?
Start monitoring for free with Webalert →
Explore features or see pricing.
1-minute checks. Multi-region monitoring. Instant alerts.