How to validation API inputs?

Harry 455 27 Jan 2026

Harry

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1 Answers

Harry 27 Jan 2026

API input validation means checking incoming data to make sure it’s correct, safe, and expected before processing it.

Common ways to validate API inputs:

Check required fields
Ensure mandatory parameters are present.
Example: email, password must not be empty.
Validate data types
Confirm inputs match expected types (string, number, boolean, array).
Apply format rules
Use patterns or rules:
- Email format
- Date format (ISO 8601)
- Phone number pattern
Set length & range limits
- String length (min/max)
- Number range (e.g., age 1–120)
Whitelist allowed values
Accept only known values (e.g., role = admin | user).
Sanitize inputs
Remove or escape harmful characters to prevent SQL injection, XSS, etc.
Use validation libraries
Examples:
- Node.js: Joi, Yup, Zod
- Java: Hibernate Validator
- Python: Pydantic, Marshmallow
Return clear error responses
Send meaningful messages with proper HTTP status codes (e.g., 400 Bad Request).

Best practice: Validate inputs at the API boundary before business logic runs.

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How to validation API inputs?

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1 Answers

Common ways to validate API inputs: