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A mock server lets you stand up a fake API in seconds. Instead of waiting for a backend to be built or deployed, you define the routes and the responses yourself, and Requestly serves them from a hosted URL that you can call from your app, your tests, or any HTTP client. Reach for a mock server when you are developing against an API that does not exist yet, when you need to reproduce an edge case on demand (a 500, a slow response, a specific error body), or when you want to give your frontend a stable target while the real service is still in flux.

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Prerequisites

Mock Server runs in the cloud, so you need to be signed in and working inside a cloud project (a private or team project synced to your account). It is not available for local projects.
Sign in from the top-right menu, then make sure a cloud project is active in the project switcher before you continue.

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Find the Mock Server

Open the Mocks section in the left sidebar of the API Client. This is where every mock server in the active project is listed. A colored dot next to each name shows whether it is currently serving: green and pulsing means active, grey means stopped.
The Mocks section in the API Client sidebar showing a list of mock servers with status dots and a create button

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Quickstart: your first mock in 60 seconds

The fastest way to understand a mock server is to serve one response and call it. This walkthrough creates a GET /hello endpoint that returns a small JSON payload.
1

Create the mock

In the Mocks section, click the + button (or the Create mock button in the empty state), enter a name, and click Create. The mock opens in a new editor tab, already scaffolded with one route and one response so you have a working starting point.
The Create mock server dialog with a name field
2

Define the route and response

Select the scaffolded route and set its Method to GET and its Path to /hello. In the response pane, on the Body tab set the status to 200 and enter this body:
On the Headers tab, add Content-Type with the value application/json so the caller receives it as JSON. Inline bodies do not get a content type automatically.
3

Save and start serving

Click Save in the URL strip to persist your edits, then click Start to make the mock live. The status dot in the sidebar turns green.
4

Copy the URL and call it

Copy the endpoint URL for the route, then call it from any HTTP client:
You get back exactly the status and body you configured:

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The mock URL

Every mock server has its own hosted URL of the form https://<id>.mocks.requestly.cloud, shown in the strip at the top of the editor. Each route lives under that base URL at the path you give it, so a route with path /users is served at https://<id>.mocks.requestly.cloud/users. To copy a full endpoint URL, hover a route in the routes list and click the copy icon, or use the copy button next to the path field in the response pane. Paste it into your app or another request to call the mock. When you run against a local development build, the base URL uses a .localhost host and an explicit port instead (for example http://<id>.localhost:8091); the cloud URL above is what you use in production.
A mock only serves traffic while it is running. Click Start in the URL strip to begin serving and Stop to take it offline. A request to a mock that is stopped returns 503. The status dot in the sidebar reflects the current state.

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The editor at a glance

The mock editor is a two-pane tab. The left pane lists the routes, and the right pane configures the responses for whichever route is selected. Each response has its own Body, Headers, and Rules sub-tabs.
The mock server editor with the routes list on the left and the response configuration pane on the right
Edits to routes, responses, and rules are staged until you click Save in the URL strip. Navigating away from a mock with unsaved changes prompts you to save or discard.
Once you have the basics working, dig into each part of the editor:

Routes

Match requests by method and path, capture path parameters, use wildcards, and control which route wins when two overlap.

Responses & selection modes

Configure the body, status, latency, and headers, insert dynamic values, and choose how the mock picks a response.

Matching rules

Serve a different response depending on the incoming request’s query, header, body, cookie, or URL parameter.