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API Fast Mock
Ultra-Compact Stateless Mocks
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Stateless · No database · One shareable URL

Mock any API in seconds

Design a response, toggle the behaviors you need, and we pack the entire spec into a single compact token. Watch it build live on the right — then share the link. That's it.

You're editing an existing mock. Adjust anything and regenerate to get a fresh token (the old link keeps working too).
Quick start

Start from a template

Pick a preset to fill everything instantly — then tweak. Or build from scratch below.

Step 1 · Essentials

The basics

Every mock needs a method, a status code and a response body.

200 OK 201 Created 404 500
Tip: leave empty to use a sensible default.
Step 2 · Optional

Advanced powers

Flip on only what you need. Each one adds realistic behavior to your mock.

API Key Authentication
Require an X-API-Key header
Callers must send X-API-Key: your-secret-key or they get a 401.
Latency & Timeout
Simulate slow networks or gateway timeouts
Wait this long before responding (0–30s). Great for testing loading states.
Returns 504 Gateway Timeout after the given delay.
Random Failures
Fail a percentage of requests with 500
Chance each request randomly returns 500 Internal Server Error.
Dynamic Fields
Generate UUIDs, timestamps, counters & random values

Point to a key in your response (e.g. id or user.token) and we'll fill it fresh on every call.

Request Validation
Reject requests missing required params
Comma separated. Missing any → 400.
Field → expected type (string / number).
Conditional Responses
Return different data based on the request

First matching rule wins; otherwise the default response is used.

Rate Limiting
Cap requests within a time window
Exceeding the limit returns 429 Too Many Requests.
Response Sequence
Cycle through responses on each call
Each request returns the next item, then loops back to the start.
Webhook Callback
Notify a URL after responding
Fire-and-forget callback triggered after the mock responds.
CORS enabled
Allow browser requests from any origin

Your mock is live

Copy the URL and start calling it — or test it right here. Don't lose the edit link below.

 Mock URL GET
 Token — B

Save your edit link

There's no database — this is the only time you'll see the edit link. Save it to change this mock later.

Try it live

Send a real request to your mock and see exactly what callers get.

Use it in your code