SP REST JSON modifies the accept property in the request header for SharePoint REST API calls to get the response in JSON format and to show it directly in Firefox instead of downloading a XML file.
Works for on-premises and SharePoint online.

SP REST JSON - Modify SharePoint API Calls in Firefox
SP REST JSON is a Firefox add-on that allows you to modify the accept property in the request header for SharePoint REST API calls. It changes the response format to JSON and enables direct viewing in Firefox instead of downloading XML files.
Add-on stats
Manifest V2
Weekly download count: 2
Firefox on Android: No
Permissions:
- <all_urls>
- activeTab
- tabs
- storage
- webRequest
- webRequestBlocking
Size: 79.09K
Email: da*****@gmx.de
URLs: Website
Full description: See detailed description
Ranking
User reviews
This extension makes debugging the REST API possible with FireFox since MS decided to use an ATOM/XML content type and hose FF apparently by default. Thank you!
by Firefox user 15182386, 2019-08-02
Add-on safety
Risk impact
SP REST JSON requires some sensitive permissions that could impact your browser and data security. Exercise caution before installing.
Risk impact analysis details
- Critical Allows access to all websites, posing a significant security risk as it can monitor and modify data from any visited site.
- Critical ****** ****** ** ******* ***** ***** *** ** **** ** ***** **** ******** ****** *** ******** ********** * ******* ********
- High ******* ******* **** *** ****** ***** *** ***** ** ******* **** ********* ********* ** * *********** *****
- Low ******* ****** ** *** ********* ********
Risk likelihood
We don't have sufficient data to confidently determine the risk likelihood of SP REST JSON. Use it at your own risk.
Risk likelihood analysis details
- High This extension has low user count. Unpopular extensions may not be stable or safe.
- Low **** ********* *** ******* **** **** * ****** **** ***** ******** *** **** ****** ** ** ****** *** *****
- Low **** ********* *** ***** **** **** * ****** **** ***** ********** *** **** ****** ** ** ****** *** *****
- Good **** ********* *** **** **** *******
Upgrade to see full risk analysis details