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Makes JSON/JSONP easy to read.
Branch: master
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nikrolls Move to using WebExtension APIs for CSS injection
This is to prevent it being blocked on sites with CSP headers.
Latest commit afd0f57 Feb 4, 2018

JSON Formatter

Browser extension for printing JSON and JSONP nicely when you visit it 'directly' in a browser tab.


  • JSONP support
  • Fast, even on long pages
  • Works on any valid JSON page – URL doesn't matter
  • Syntax highlighting with 36 light and dark themes
  • Collapsible trees, with indent guides
  • Line numbers
  • Clickable URLs
  • Buttons for switching between raw and parsed JSON
  • Parsed JSON is exported as a global variable, json, so you can inspect it in the console

A background worker is used to prevent the UI freezing when processing very long JSON pages.


Option 1 – Install it from the Chrome Web Store or Windows Store.

Option 2 – Install it from source:

  1. Clone/download this repo
  2. Install dependencies using NPM or Yarn.
  3. Build the extension: gulp build:dist
  4. Side-load the extension in your browser as per below


  1. Open Chrome and go to chrome://chrome/extensions/
  2. Enable "Developer mode"
  3. Click "Load unpacked extension"
  4. Select the build folder created in step 3


  1. Open Edge and go to about:flags
  2. Enable the option "Enable extension developer features" and restart the browser
  3. Click on the ellipsis (...) menu, click "Extensions", and click "Load extension"
  4. Select the build folder created in step 3

Some URLs to try it on:

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