How to design API filtering and sorting

· Category: API & REST

Short answer

Filtering and sorting query parameters let clients retrieve precisely the data they need, reducing payload size and improving usability.

Steps

  1. Define filter operators such as eq, neq, gt, lt, contains, and in.
  2. Accept sort as a comma-separated list with optional direction prefixes like asc and desc.
  3. Support field selection via a fields or include parameter to limit response size.
  4. Validate and sanitize all query inputs to prevent injection attacks.
  5. Document supported filters, sortable columns, and default ordering.

Tips

  • Use consistent naming conventions for query parameter keys.
  • Escape special characters in filter values to avoid parsing ambiguities.
  • Limit the complexity of nested filters to maintain query performance.
  • Return 400 for unsupported filter fields rather than ignoring them silently.

Common issues

  • SQL injection through unsanitized filter parameters.
  • Sorting on unindexed columns causing full table scans.
  • Inconsistent handling of null values in range filters.
  • Overly complex query strings exceeding URL length limits.

Example

curl -X GET https://api.example.com/users   -H "Accept: application/json"   -H "Authorization: Bearer $TOKEN"

This curl command demonstrates a standard GET request with headers for content negotiation and bearer token authentication.