This translator generates subscript (ₗᵢₖₑ ₜₕᵢₛ) which you can copy and paste. It is actually converting your text into a subset of the Unicode standard. This is why you're able to copy and paste subscript characters around the place (e.g. facebook, tumblr, twitter, reddit, instagram bio etc.).
Note that the Unicode spec doesn't contain subscript characters for all of the numbers and letters so in this converter I've had to find the nearest characters which look like superscript versions, or just use the regular character if there isn't anything similar. Perhaps the cheekiest substitution that I've done here is converted "w" into two subscript "v" characters, since there is no subscript version of "w". I know, it's not fooling anyone...
This means that you'll have to get creative if you're trying to write something in superscript letters when the words you want to use have characters for which there is no Unicode subscript equivalent.
Note that the small sub-script characters generated by this tool will work in many different websites (when you copy and paste it into your post/tweet/etc.) but some websites have banned all Unicode characters other than a specific subset (e.g. the letters and numbers on your keyboard, and perhaps some symbols), so if you try to post the subscript letters somewhere and it doesn't work, then it could be that that website has "banned" subscript text (and perhaps other fancy text types) for some reason - e.g. because people were "abusing" it to make their posts stand out more or something.