Simple In Browser Debugging for APIs

Mocking API Network Requests with The Inspector

One difficult part of building an API is mocking and modifying the requests your application will receive. There are lots of tools out there, like Postman, but those are heavy tools to use early in the development process or for simple testing. Instead, there is a simple way of copying, editing, and re-running HTTP requests directly in the inspector.

Image of Firefox's Edit and Resend Tool In Use


The Firefox browser inspector comes bundles with some great developments tools. Two of my favorites are the CSS grid inspector and this API debugging miracle: “Edit and Resend”.

Network Inspector

If you’re a seasoned developer, you might know and love the Network Monitor. If you’re newer or haven’t ever checked it out, I really encourage you to watch a few dozen web requests pass by while looking at the tab. It gives you a lot of insight into how the web works.

Edit and Resend

To use this tool, open the Network Monitor tab of your Inspector in Firefox. Make your first HTTP request by visting a URL. In the image, I’m visiting localhost:8000/api/users/create, which creates a GET request for that resource.

Making a GET request to my API

In my application, the endpoint only accepts POST requests, so the application throws an error. Time to break out some cURL or fetch(), right? There’s an easier solution! I can right click the request, then select Edit and Resend to modify the request right in the browser.

Locating the Edit and Resend tool

I changed the HTTP request method to POST, and added some data to the request body.

Making any changes to my API request

Now when I click the send button, I can see that my API is reponding as expected. It’s 201 season, friends!

After tweaking, the API handles my request!

Pack It Up and Take It Away!

Once your API request is properly formed in the browser, and your API or application is returning the results you expect, how do you export that request to another application? Again, the browser makes it easy. Right click your working request, then copy it into the format you want. Now you can use your working request anywhere in your code!

Copying my API request for use in my application.