Download of SimplyJSON 1.2 for Mac was on the developer's website when we last checked. We cannot confirm if there is a free download of this app available.
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. This free Mac app is a product of Adil Erchouk. The software lies within Developer Tools, more precisely Webmaster Tools.
From the developer:
SimplyJSON is a simple JSON viewer that installs as a Safari extension. The application can expand or collapse items in the JSON file. Therefore, the utility shows JSON data in collapsed or expanded formats. In addition, the tool supports showing the source of a JSON file.
You may want to check out more Mac applications, such as Url Extractor X, Boks or Navicat for Oracle, which might be related to SimplyJSON.