Fast non-blocking JSON viewer for Chrome and Firefox
Clone or download
lauriro Fix race condition with jsonp
sendResponse and executeScript does not run in order
Latest commit ad8388e Oct 27, 2018


Browser extension for viewing JSON files.


  • Format JSON and JSONP responses
  • Select and format JSON on every page
  • Collapsible arrays, objects and long values
  • Collapse all childs with Ctrl(Command) + Click
  • Collapse property also on all sibling items with Alt(Option) + Click
  • Count items and properties in a collection
  • Show collection sizes
  • Do its best to show large (10MB+) JSON files
  • Do its best to show invalid JSON files
  • Do not sort objects with numeric keys
  • Do not round large numbers
  • "Save as..." saves the original JSON document
  • Select and copy a working JSON from the formatted JSON


  • Disable Firefox built-in JSON viewer
    Go to about:config and set 'devtools.jsonview.enabled' to false



Copyright (c) 2016-2018 Lauri Rooden
The MIT License