Tools

Online:

Regex101 – useful for testing your regex patterns

jsFiddle – test your html / java and css configurations

dotnetfiddle – test your .Net code

hexed.it – online hex viewer

fishbowlie – online FPS test for your browser

https://stackedit.io/ – Really cool online markdown editor

https://www.unitjuggler.com – great tool for converting different units

https://jsonschema.net/ – great for generating json schema i.e. for AWS

Offline:

Spacesniffer : which I find the one of best tools to quickly see what is taking space on your drive

Etcher – Great multiOS tool to burn out bootable ISOs into USB. Simple and effective