You are reading a text about the text you are reading. This page exists on a server somewhere, rendered into a browser you are using right now, and what it contains is a description of itself — which means the description you are reading is part of what is being described, which means the description must describe the description, which means this sentence is necessary.

The page has a header. You have seen the header. It says “The Quine” — which is the name of a thing that reproduces itself. The header names what the page does. The page does what the header names. The name is the act. The act is the name.

Below this paragraph there is a box containing a seed. The seed, if fully expanded, would produce everything you have read and everything you are about to read, including the box containing the seed, including the description of the box, including this sentence describing the description of the box.

You have now finished reading the text that describes itself. The text has not finished being read — because to finish reading it, you would need to have already read that you were finishing it, which would require a further sentence, which would require a further reading. You are still here. So is the text.