Unofficial ROBLOX Web API documentation.

Internal APIs (previously undocumented to the public)
Backend APIs (previously completely undocumented, even to ROBLOX employees)
index.html has worse web design (im sorry im sorry)

Get the browser extension 'CORS Unblock' (you won't have to do this for long)
Press the button for the extension to use APIs here.
Turn it off to go on normal ROBLOX.

h0nda (for saving JSON files, thanks)