What is the difference between registering as a British citizen and naturalising?

Registration recognises a connection to the UK that already exists in law. For example, someone born in the UK who lived here until they were 10, or a child whose parent later became British or settled, may have a right to register rather than apply from scratch.

Naturalisation, by contrast, is the standard adult route based on residence, settled status, and meeting the good character, English language and Life in the UK requirements. If you qualify to register, that is usually the more direct path, so it is worth checking your eligibility before assuming you must naturalise.