In one paragraph
A .pub file is a document made in Microsoft Publisher, the page layout program Microsoft has sold since 1991. Where Word flows text down a page, Publisher places boxes on a page: a text box here, a picture there, a shape behind them, on a page of a fixed size. That is why Publisher was the tool of choice for flyers, bulletins, newsletters, business cards, labels and certificates, and why a .pub file is nothing like a Word file inside.
What is inside the file
Technically, a .pub file is a Microsoft compound document (the same container format as old .doc and .xls files) holding a set of streams that describe pages, the objects on each page, the text in each text box with its formatting, and the pictures embedded in the document. Its MIME type is application/x-mspublisher.
Microsoft has never published a specification for it. The format is not covered by the Open Specifications Promise that documents .docx and .xlsx, so every program that reads .pub files outside Publisher does so with a reverse-engineered reader. One open-source option is libmspub, an open-source library from the Document Liberation Project. LibreOffice, Scribus and stillPUB all read .pub files through it, but each application has its own import pipeline and rendering behavior.
Which versions convert, and which do not
- Publisher 2000 through Microsoft 365 (file format versions from 2000 onward): text boxes, pictures, shapes, page sizes, fills, borders and most text formatting convert well.
- Publisher 97 and 98: an earlier format with limited support. Expect missing pieces.
- Publisher 95 and earlier: effectively unreadable outside Publisher.
WordArt, master pages and linked text boxes can lose editing structure during import. Read the conversion warnings and compare every page. A recognised version or an empty report is not a guarantee of full fidelity.
Why nothing else opens it
Word and PowerPoint have never had a .pub import filter, and Microsoft's own advice for the October 2026 retirement is to convert files to PDF first. Canva and Affinity do not import .pub either. Google Drive shows the file as a generic blob. Some conversion services upload files; others process them locally. Check the particular service and its outputs.
Opening one today
stillPUB is a free pub file reader that runs in your browser without uploading the file, keeps it editable, and exports PDF, JPG and PNG. You can view .pub online, no install, the same way on Windows, Mac, Linux or a Chromebook. The step-by-step version is on how to open a .pub file without Publisher. If you only need a PDF, convert a .pub file to PDF covers the fastest route.
Related extensions
- .pub: the Publisher document. This page.
- .pubx: not a real Publisher format. Publisher never adopted an XML-based successor the way Word moved from .doc to .docx.
- .stillpub: stillPUB's own editable save format, a JSON document with the pictures embedded. stillPUB uses it to save editable projects; it does not include a .pub writer.
- .epub: an e-book format. Unrelated.