DEV Community

Kiran Johns for Hoppscotch

Posted on • Updated on

Testing your APIs locally using Hoppscotch

Hoppscotch provides you with a fast and easy platform to design and test your APIs. One major benefit of using Hoppscotch is that you can begin using it immediately from your web browser without any downloads or sign-up requirements. However, as this version of Hoppscotch operates within your browser, you will need to install and configure the Hoppscotch web extension to test locally hosted APIs due to the same-origin policy in the cross-origin resource sharing mechanism.

Cross-Origin Resource Sharing (CORS) regulates the sharing of resources between two distinct domains. To prevent malicious interactions and enhance data security, CORS employs a strict same-origin policy that restricts a website's ability to access resources beyond its host domain. As a result, the Hoppscotch web client necessitates the installation of an extension to actively manage CORS and enable access to APIs on your local server. If the extension is not installed, you will encounter an error message when attempting to actively send a request to localhost.

Error on Hoppscotch when attempting a request to localhost

The Hoppscotch web extension

The Hoppscotch web extension enables requests across origins and overrides CORS restrictions, allowing requests to be made to localhost. To download the extension, follow the links below for Firefox and Chromium-based web browsers.

  1. Hoppscotch web extension for Firefox
  2. Hoppscotch web extension for Chrome / Chromium

To enable the Hoppscotch web extension, select the Hoppscotch icon in your browser extensions. Then specify the origins that can connect to the extension. If you're using Hoppscotch cloud then the active origin list should contain

Now refresh the Hoppscotch web app and change the middleware to the browser extension in the interceptor section on the settings page.

Hoppscotch interceptor settings

Using Hoppscotch to test local APIs

You now have successfully configured Hoppscotch to allow requests to localhost. Let's test this by creating a mock API using json-server.

First, install the json-server package using npm

npm i -g json-server
Enter fullscreen mode Exit fullscreen mode

Create a file db.json somewhere on your desktop or inside a new folder and copy-paste the following JSON into the file

  "posts": [
    { "id": 1, "title": "hoppscotch-rocks!", "author":"you" }
  "comments": [
    { "id": 1, "body": "one hopp to rule em all", "postId": 1}
  "profile": { "name": "ilovehoppscotch" }
Enter fullscreen mode Exit fullscreen mode

Now, start the json-server by running the command below

json-server --watch  db.json
Enter fullscreen mode Exit fullscreen mode

You’ll get the below response in the terminal if the server starts successfully

 \{^_^}/ hi!

  Loading db.json



  Type s + enter at any time to create a snapshot of the database
Enter fullscreen mode Exit fullscreen mode

Now, if you visit the Hoppscotch web client and send a request to http://localhost:3000/posts or any of the above endpoints, you will receive a JSON response.

Hoppscotch configured for localhost

Just like that, you can easily configure the Hoppscotch web client to send requests to your local server and immediately get started with your API development. You can begin using Hoppscotch right now by visiting You can also stay connected with us by joining our Discord server and following us on Twitter at @hoppscotch_io.

Top comments (0)