The original version was published in Volo’s Guide to Monsters, then republished without changes in Explorer’s Guide to Wildemount. The Tabaxi effectively has three versions. Portions of the materials used are property of Wizards of the Coast.
RPGBOT is unofficial Fan Content permitted under the Fan Content Policy.
Only problem is the base sheet only has SRD content due to a WotC limitation (since it's a buyable product), so you'll have to import scripts from here if you want the rest of the content (including expansions!), or other homebrew people have come up with. (Disclaimer: It's less of a step-by-step guide for new players and more of an automated sheet for experienced players to super quickly write out a new character, though).
#TABAXI 5E CHARACTER BUILDER FULL#
Also has full descriptions of all class features and spells.
#TABAXI 5E CHARACTER BUILDER PDF#
It's not online, but it's a PDF that calculates almost everything automatically and has a ton of automation for levelling up and adding features. Highly recommend MPMB's Character Sheet (yes, it is literally named that) if you want autocompleting character sheets.