4xx Client Error

HTTP 422 Unprocessable Content

The server understands the content type and syntax of the request, but it was unable to process the contained instructions. Often used for semantic validation errors where the request is well-formed but logically invalid.

Common Causes

  • Validation errors on form fields (e.g., invalid email format)
  • Business logic violations (e.g., end date before start date)
  • Required fields present but containing invalid values
  • Semantic errors in a syntactically correct request

How to Fix

  1. 1Check the response body for specific validation error details
  2. 2Fix the data according to validation rules and resubmit
  3. 3Validate input on the client side before sending
  4. 4Review API documentation for field constraints

Example

HTTP 422 Unprocessable Content
POST /api/events HTTP/1.1
{ "start": "2024-12-31", "end": "2024-01-01" }

→ 422 Unprocessable Content
→ "End date must be after start date"

Related Client Error Codes

400

Bad Request

401

Unauthorized

402

Payment Required

403

Forbidden

404

Not Found

405

Method Not Allowed

406

Not Acceptable

407

Proxy Authentication Required

408

Request Timeout

409

Conflict

410

Gone

411

Length Required

412

Precondition Failed

413

Content Too Large

414

URI Too Long

415

Unsupported Media Type

416

Range Not Satisfiable

417

Expectation Failed

418

I'm a Teapot

421

Misdirected Request

423

Locked

424

Failed Dependency

425

Too Early

426

Upgrade Required

428

Precondition Required

429

Too Many Requests

431

Request Header Fields Too Large

451

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