The short answer
Reddit treats a finalized username as permanent, including its capitalization. Changing a profile display name does not replace the u/ name on posts or your account URL. If a tutorial promises a hidden rename button for a finalized username, check it against Reddit’s own help page before following it.
If you only want a different profile label
Open your profile editing controls and look for the display-name field. Choose a label that matches your interests without revealing your school, full birthday or other private details. View the public profile after saving: the display label can change while the underlying username stays the same. Interface labels can vary between the app and website.
If you need a different u/ identity
Create a separate account with the username you want, following Reddit’s current signup flow. You can keep the original account; do not delete it just to release its name. Reddit says deleting an account does not make that username reusable. A new account is a separate identity, so plan how you will find communities and introduce yourself again.
Choose something you can keep
Make a shortlist of three to five handles. Read each one aloud, check that it is easy to spell, and remove personal identifiers. A neutral interest or invented word often ages better than a passing joke. Use our username ideas collection to explore options, then confirm the final choice inside Reddit.