X has no real "delete everything" button. If you want to clear years of old posts but keep your handle, here are the actual options, the limits nobody mentions, and the fastest safe way to do it.
You can deactivate your whole account, but then you lose your username and followers. There is no built-in tool that wipes your posting history while keeping the account active. So clearing old tweets means either deleting them one at a time, or using a third party tool. Deleting by hand is a non-starter once you have more than a few dozen.
These connect to your account through X's API and delete in bulk. They work, but two things trip people up. First, X only exposes your roughly 3,200 most recent tweets through the API, so older posts will not be reachable unless you upload your X data archive. Second, many are subscription based and you are granting a third party API access to your account.
A browser extension does the deleting inside your own browser, on the session you are already logged into. It scrolls your timeline and clicks X's own delete buttons for you. Nothing leaves your machine and you do not hand over API keys. Because it works off the visible timeline, it can also chip past the 3,200 wall over repeated passes: as the newest posts are deleted, older ones load in.
Will I lose my username? No. Clearing posts keeps your handle, photo and bio. Only the content is removed.
Is it safe? A local browser tool never asks for your password or API keys. It only acts on the account you are already logged into.
How long does it take? Small accounts can finish in minutes. Large ones take longer because of rate limits, but a good tool resumes automatically.