Quick answer
API security best practices are the controls that protect the interfaces apps use to exchange data. They include strong authentication, object-level authorisation, input validation, rate limiting, encryption in transit and monitoring, and follow OWASP's API Security Top 10.
Key takeaways
- Authenticate every request and check permissions for every object.
- Validate and limit all input.
- Use HTTPS everywhere and rate-limit requests.
- Log activity and review it.
What are the most common API weaknesses?
| Weakness | What it looks like |
|---|---|
| Broken object-level authorisation | A user changes an ID and sees another person's data |
| Weak authentication | Guessable keys, no expiry |
| Excess data exposure | API returns fields the app does not need |
| No rate limits | Attackers try thousands of requests |
| Old versions left running | Forgotten endpoints with known flaws |
How do you control access?
- Use a proven standard such as OAuth 2.0.
- Give each user and app only the access it needs.
- Check permission on every object, not just on login.
- Expire and rotate keys and tokens.
How do you protect the data itself?
- Send everything over HTTPS.
- Validate type, length and format of every input.
- Return only the fields required.
- Keep secrets out of code and URLs.
- Encrypt sensitive data at rest.
What about monitoring?
Log requests, failed logins and unusual patterns, and alert someone who can act.
Keep an inventory of every API, including old versions, and retire what you no longer use.
Test before attackers do
Run automated security scans and regular penetration tests. Review third-party APIs too, as their weaknesses become yours.
A short review checklist
- Does every endpoint require authentication?
- Can a user ever view another user's data by changing an ID?
- Are there rate limits on login and search?
- Do error messages reveal system details?
- Are old API versions still live?
If you answer yes to the last two or no to the first three, API security best practices need attention now.
Start with the most exposed endpoints.
Bottom line
API security best practices come down to this: check who is asking, limit what they can reach, validate everything that comes in and keep logs. Most API breaches come from basics that were skipped.
Sources and further reading
- OWASP API Security Project
- Australian Cyber Security Centre: Essential Eight
- Open Worldwide Application Security Project
Checked against the sources above and our own project experience. Last reviewed 7 October 2026.
