Javascript only implementation of Base91 (all-imaginable-browser support). Weights only 1kb minified.
Encode:
base91.encode('Hello World, remember to call your mom and tell her you love her!');
// outputs: '>OwJh>Io0Tv!mxcLdPLg`<aeKUd/[E>i;iwJR`0eLUr#O9kLpo;I9[(*FTo4|alLwrdKE<Sk<Ro4|a*L'
Decode:
base91.decode('>OwJh>Io0Tv!mxcLdPLg`<aeKUd/[E>i;iwJR`0eLUr#O9kLpo;I9[(*FTo4|alLwrdKE<Sk<Ro4|a*L');
// outputs: 'Hello World, remember to call your mom and tell her you love her!'
You can play with it here; https://jsfiddle.net/6zyhg8k0/1/
(This project is completed and won't be getting any new updates unless necessary)