I have created a very small userscript for opera (might work ok with other browsers) that formats /indents/ beautifies the JSON data in a document if it's only JSON there. For opera to open the JSON by itself and this to work (the default is to present it as a download), you will have to enable that in opera. Go to preferences -> advanced -> downloads -> Add Mimetype: application/json Select open with opera That will result in your JSON looking like this in the browser: 

 //== UserScript == 
 // @name JSON formatter 
 // @version 1.0 
 // @description Formats JSON if the document only contains JSON 
 // @compability Only tested with Opera, might work with others 
 // @author Martin Hansen 
 // @website http://martinhansen.no 
 // ==/UserScript== 

 (function(){ var indentation = 4; //Change this to vary the indentation
     var pre = document.querySelector('body pre:only-child');
     if (!pre) return; //Don't do anything if this don't seem to be a json only document
     try {
         pre.innerHTML = JSON.stringify(JSON.parse(pre.innerHTML), null, indentation);
     } catch (e) {
         console.log(e);
     }
 })();

Either save the sourcecode directly from here, or get it from userscripts.org

Comments

Paul Fenwick: Works perfectly in Firefox/Greasemonkey, and just made my life much, much easier! Thank you!