Install the app and run it. This will register the availability of the app’s QuickLook extensions, JSON Previewer and JSON Thumbnailer. You can now quit the app: just click OK:
To use QuickLook in Finder, select a JSON file — one with the extension
.json — and press space. This will pop up a rendered preview of the file, either as pure data:
Or including JSON markers:
You will also see JSON file previews in Finder’s preview pane, enabled using View > Show Preview or by hitting Cmd-Shift-P, and in the Preview: section of Finder’s file info panel (select a file and hit Cmd-I).
You can disable or re-enable JSON Previewer and/or JSON Thumbnailer in System Preferences > Extensions:
For some background information on how Catalina delivers QuickLook previews, you might like to read this blog post.
Open the Preferences panel from the main app’s PreviewJson menu. This allows you to adjust some of the key elements of the preview:
}) and arrays (
Choose your preferred text size using the slider, then pick the monospace font you want the file to be presented in:
Choose your preferred key colour by clicking the colour well to pop up macOS’ colour picker. As you make your colour selection, the colour well will be updated:
Click Save to apply your choices.
Changing these settings will affect previews straight away, but may not affect thumbnails until you open a folder that has not been previously opened during the current login session.
You can use the main app to submit feedback. Just click in the Send Feedback button in the main window, or select Report a Bug… from the Help menu:
If PreviewJson reports that it was unable to render JSON, this is almost certainly caused by a malformation of the JSON itself. For this reason, you can optionally tell PreviewJson to display a file’s raw JSON in the event of a parsing error. This option is chosen in the Preferences panel and will allow you to QuickLook even bad JSON files, just without rendering.
If you have found PreviewJson to be useful, please consider writing a positive review on the Mac App Store, or simply give it a rating.
You can view PreviewJson’s source code at GitHub.