A self-hosted DTMF (dual tone, multi frequency) encoder/decoder. That's a fancy way of saying that you load it in your browser and it gives you a dialpad (0-9, *, #, A-D) that you can peck at and it'll generate DTMF tones. It also can hook your microphone through your browser, listen to DTMF tones, and tell you what they mean.
npm install --legacy-peer-depsyarn buildyarn startis a good way of kicking the tires.
Everything in build/ should be handled by a web server.
You'll have to hand-hack the /index.html file because it's hardcoded for /DTMF-Tool/ instead of /. I should probably file a bug for that.
A collection of tools, calculators, converters, generators, encoders, decoders, and more of common use to IT. Can be built by hand but it's probably easier to download the latest release and unpack that.
Decode UTF-8 into ASCII and vice versa.
An online password generator/decoder for the Mega Man games, Castlevania 2, Metroid, Solar Jetman, the Guardian Legend, Faxanadu, and Battle of Olympus. Pick the options you want and it'll build you a password. Type in a password and it'll show you what it means.
Software that takes an image and encodes it as sound. If you look at the spectrogram, you can see the image again. Remember that Aphex Twin album? That. The encoder is Javascript, open the page in your browser. Open result.wav with a spectrogram utility (like Sonic Visualiser) and you can see the image.