FormatExpress is an easy-to-use online formatter where you simply paste some bunch of raw XML, JSON, CSS or SQL, to get it automatically beautified. The most common use-case is to help reading minified input found in logs or web services.
A site that converts UNIX style time_t timestamps into human readable time/date stamps.
A simple app to make your calculations easier. Self-hostable.
Github repos for the three components: https://github.com/keepformula
CyberChef is a simple, intuitive web app for carrying out all manner of "cyber" operations within a web browser. These operations include simple encoding like XOR or Base64, more complex encryption like AES, DES and Blowfish, creating binary and hexdumps, compression and decompression of data, calculating hashes and checksums, IPv6 and X.509 parsing, changing character encodings, and much more.
The tool is designed to enable both technical and non-technical analysts to manipulate data in complex ways without having to deal with complex tools or algorithms. It was conceived, designed, built and incrementally improved by an analyst in their 10% innovation time over several years.
Online copy: https://gchq.github.io/CyberChef/
An online JSON editor, formatter, and explorer, which should be handy for many things.