The Complete Guide to API Monitoring in 2026

Your frontend might be up, but if the API is slow or returning errors, users still suffer. Here's how to monitor APIs properly.

Why API Monitoring is Different

Websites return HTML. APIs return JSON. The monitoring strategy differs:

• Check HTTP status codes (200 OK vs 500 errors)
• Validate response body content
• Measure response time (latency)
• Test authenticated endpoints

Setting Up API Monitors

Step 1: Choose Critical Endpoints

Don't monitor everything. Focus on: login, core business logic, payment processing, and third-party integrations.

Step 2: Add Authentication

Most APIs require auth. Configure headers (Bearer tokens) or basic auth in your monitor.

Step 3: Set Response Assertions

A 200 status isn't enough. Validate the response contains expected data. For example, check that {"status": "healthy"} is present.

Latency Thresholds

APIs should respond quickly. Set alerts for P95 latency exceeding 500ms. Slow APIs degrade user experience even when "up."