What is a .pub file? (and why it needs Publisher)

The .pub format is Microsoft Publisher's private file type — a desktop-publishing document that was never meant to travel. A short explainer before you decide what to do with yours.

A .pub file is a Microsoft Publisher document: a page-layout file that stores text boxes, pictures, and their exact positions on the page. Publisher was aimed at homes, churches, schools and small offices — which is why so many bulletins, newsletters, flyers and certificates live in this format.

Unlike Word's .docx, the .pub format was never opened up for other programs to use; only LibreOffice ever taught itself to read it, and imperfectly. That was fine while every office PC had Publisher; it becomes a problem when the program goes away, which is exactly what happens on October 1, 2026. For anything you want to keep, the durable choices are PDF (looks identical, opens everywhere) and Word (keeps the text editable).