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2026-07-29 16:01
REST API

409 Conflict

ErrorValidateRequestMedium
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What you will learn

  • 409 Conflict fires on state-dependent failures (duplicate email, version mismatch on update) — distinct from 400 Bad Request (malformed input)
  • On optimistic-concurrency 409, return the current version/ETag so the client can retry after re-fetch
  • Test from concurrent clients — 409 must fire for exactly one (the loser), the other succeeds

Description

Handle resource conflicts like duplicate email.

Test Scenario

// Create user with existing email
const response = await request.post('/api/v1/users', {
  data: { email: 'existing@test.com', name: 'Test' }
});
expect(response.status()).toBe(409);
Endpoint/api/v1/errors/409

Testing Tips

  • •Create duplicate resource
  • •Check conflict field in error
  • •Common for unique constraints
// Playwright API Testing - REST
import { test, expect } from '@playwright/test';


test('REST API request', async ({ request }) => {
  const response = await request.get('/api/v1/resource');


  expect(response.ok()).toBeTruthy();
  expect(response.status()).toBe(200);


  const data = await response.json();
  expect(data).toBeDefined();
});

Challenge ID: rest-error-409

2 frameworks available

API Playground

Send requests and inspect responses

Endpoint: /api/v1/errors/409

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