This page contains various online tools that I have found helpful during my programming day. The aren’t needed or even particularly relevant to tutorials here on I keep this list as much for myself as anything else, but if you also find them useful, great!

JSON Formatter and Validator : Validate your JSON object online. Also great for reformatting JSON objects to and from compact and “pretty” format.

Online GUID Generator: Create GUIDs.  Lots of good formatting options such as upper/lower case, use hyphens or not, use braces or not.  Generate between 1 to 2000 GUIDs in a single shot.  Nice and simple interface.

Online Regex Editor: Create and test regular expressions online.

User Agent Decoder: Take the User-Agent header from a web request, and paste in here.  This will give you lots of information about the browser, operating system, javascript support, etc.

X.509 Decoder: Copy and paste a public X.509 certificate (e.g. “—–BEGIN CERTIFICATE—–” kind of files) in the site, and it will show you the encoded information in a nice tree format.

HAR Viewer: Did you know that if use the Developer Tools in Chrome and you are watching the network debug panel that you can save off the current list of requests and responses to a file?  It is called a HAR file, and you can generate it by clicking on “Save as HAR file” in Chrome Developer Tools (from the “F12” menu).  You can then upload that file to the HAR Viewer and review your network requests outside of Chrome at a later time.  You can use this online, or you can download the source and run it on a local web server if you are paranoid.

Advanced REST Client: This one is a Chrome Web App, not a website.  Great for testing REST API’s or OAuth2 implementations.  You’ll have to install this as an application inside Chrome to use it.

Unix Time Converter:  Convert a Unix timestamp into a human readable date, or vice-versa.

XML Formatter: Lots of options to format the XML that you paste in.  You can also use a URL as input.

Online Network Tools: Your basic traceroute and nslookup tools online.  It also has some other tools like ping and DNS Mail record analysis.