API Security Best Practices: A Practical Checklist
Authentication, authorization (BOLA), rate limiting, input validation, and data exposure — a practical API security checklist mapped to the OWASP API Top 10.
APIs have no user interface to constrain behavior, so every rule has to be enforced on the server. That makes authorization the heart of API security — reflected in the OWASP API Security Top 10, where the top risks are all authorization and authentication flaws. Use this checklist to cover the essentials.
The API security checklist
| Area | What to enforce |
|---|---|
| Object-level authz (BOLA) | Verify the caller may access the specific object on every request |
| Function-level authz | Restrict admin/privileged endpoints by role |
| Authentication | Strong auth, short-lived tokens, correct JWT validation |
| Property-level exposure | Return only needed fields; never rely on the client to hide data |
| Rate limiting & quotas | Throttle per user/key to limit abuse and scraping |
| Input validation | Validate types, ranges, and sizes; reject unexpected input |
| Inventory | Track all endpoints, versions, and deprecated/“shadow” APIs |
| Logging & monitoring | Log access and anomalies; alert on abuse patterns |
Why authorization dominates API risk
The single most common API vulnerability is BOLA/IDOR — accessing another user’s objects by changing an identifier. Close behind are broken authentication and returning too much data in responses. Get these three right and you’ve eliminated most real-world API risk.
Testing your API
Effective API testing needs documentation or a collection (OpenAPI/Postman) and test accounts for each role, so a tester can attempt cross-account and privilege-escalation attacks across every endpoint. That is precisely the scope of API Security Assurance.
Ready to test your own systems? Request a security assessment or explore Security Assurance packages.
Frequently asked questions
- What are the most important API security best practices?
- Enforce object-level and function-level authorization on every endpoint, use strong authentication and short-lived tokens, validate and constrain all input, apply rate limiting and quotas, avoid excessive data exposure in responses, log and monitor API access, and keep an inventory of all (including deprecated) endpoints.
- What is the OWASP API Security Top 10?
- It is a dedicated list of the most critical API-specific risks, separate from the web Top 10. Its top entries are Broken Object Level Authorization (BOLA), Broken Authentication, and Broken Object Property Level Authorization — reflecting that authorization flaws dominate API risk.
- How is API security testing different from web app testing?
- APIs have no UI to constrain behavior, so testing focuses heavily on authorization (BOLA), token handling, rate limiting, and data exposure across many endpoints and roles. It typically requires API documentation or a collection and testing with multiple accounts.
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