https://gchq.github.io/CyberChef/
https://it-tools.tech/
If you want a "quick" way to add a bunch more operators, all of ours are available via the 'cyberchef' NPM package[0] and the license permits embedding into other applications.
[0] https://github.com/gchq/CyberChef/wiki/Node-API
https://gchq.github.io/CyberChef/
https://it-tools.tech/