JSONPeep 1.3.2 for Mac could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The program lies within Developer Tools, more precisely Webmaster Tools. The actual developer of this free Mac application is Lev Bruk. Please check the Mac app with an antivirus before launch as it is downloaded from the developer's website, and we cannot ensure that it is safe.
From the developer:
JSON Peep is a Safari extension to view JSON in a readable format. The application runs smoothly and remains simple and easy to use. You can enjoy the Dark mode and URL highlighting. An issue which caused a mess for HTML pre-element on non-JSON related pages is now fixed.
You may want to check out more Mac applications, such as Multisite for iWeb, HyperEdit or Validator-SAC, which might be similar to JSONPeep.