They are the same when used as verbs. Rebel can be a noun. During the US Civil war the southern soldiers were called "rebels" by the Northerners

They are almost the same. I would say first, people or a person "rebels" and it develops into a larger, stronger "revolt" or "revolution"- with more violent opposition. Although to rebel can involve violence, too. Very very similar in use. Very subtle difference, and for the most part the two words can be used fairly interchangeably in common speech. An angry teenager may rebel (defy, act) against their parent or people might rebel against a new law by protesting or resisting or ignoring the law. Revolt is a stronger term - usually a group of organized people rebelling - stronger than just a protest with the intent to overturn the established government. The citizens revolted against the government and planned an attack. Revolt comes from the word "revolve" - to turn. A revolution invokes change. Maybe to "rebel" is just to push back against authority and revolt involves attempting to invoke a change by rebelling...

Rebel is a person who resists an established authority. Revolt is taking violent action against an established authority.