Can I change my username or my email?
Yes — the username can be changed twice at most, and changing your email requires a confirmation code.
Username
Settings › Account › Username. It only accepts letters, numbers and underscores, and must be unique.
Changing it is limited to 2 times per account, so choose carefully. Every link shared to your old profile stops working — remember to update your other social networks, your bio and your link in bio.
Email address
Settings › Account › Email. A confirmation code is sent to the new address: until it is entered, the old one stays active.
If two-factor authentication is on, your 2FA code will be requested to confirm the change.
Display name
Your display name, on the other hand, can be changed as often as you like from Edit profile: it is the visible label, independent from your handle.
Confirmation code never arrived? Check your spam folder and the spelling of the address — the code is only sent to the new address.