A Firefox extension that helps you view JSON documents in the browser.
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JSONView is a Firefox extension that helps you view JSON documents in the browser.

Normally when encountering a JSON document (content type application/json), Firefox simply prompts you to download the view. With the JSONView extension, JSON documents are shown in the browser similar to how XML documents are shown. The document is formatted, highlighted, and arrays and objects can be collapsed. Even if the JSON document contains errors, JSONView will still show the raw text.

Once you've got JSONView installed, check out this example JSON file to see the extension in action!

CouchDB users and others who need to have application/json sent in the HTTP Accept header to serve JSON properly should set that option in JSONView's options panel. Be aware that telling sites that you accept JSON can mess up some sites that don't expect it.

If you want to inspect a JSON snippet from your clipboard you can do so by entering data:application/json,<paste the json document> in the URL bar.

If you'd like to contribute to JSONView but don't want to code, consider contributing a translation. Copy the existing localization files from locale and src/locale and fill them in for your own language, then send a pull request. You can do it all from the GitHub interface. There's not much there to translate!

Keyboard Shortcuts

  • Left Arrow - Collapses the json on key up
  • Right Arrow - Expands the json on key up

Reporting Issues

Use the GitHub Issue tracker for JSONView to file issues. Pull requests are especially welcome.

Developing JSONView

Before contributing to JSONView, make sure to read the Contributing Guidelines. I appreciate contributions people make to JSONView, but the goal of the add-on is to be simple and straightforward, so I frequently reject contributions that add complexity or unnecessary features. Please consider filing an issue before doing any work, so you don't waste time on something I won't accept.

  • Install Add-on SDK
  • Install Firefox Nightly - the regular Firefox won't run unsigned extensions.
  • Run jpm run -b Nightly to test in Firefox Nightly.
  • Run jpm xpi to create an xpi.

The build script also comes with a HTTP server which can be used to test JSON files in tests folder. To start the integrated server, listening on port 8000, along with Firefox, run python build.py -b 8000 run.

Unofficial Ports

Common Issues

  • JSONView isn't displaying my file as JSON: You are probably not serving the JSON with the "application/json" MIME type.
  • JSONView is mangling large numbers: Here's the explanation.

JSONView is open source software under the MIT licence.