Document
What is a .prj file?
A .prj file is an ESRI Shapefile Projection (Well-Known Text) Format. This is a document format, so it holds text and layout meant to be read. Confusingly, this extension has been used by 2 different formats over the years — they're all listed below.
This extension has been used by more than one format
2 different formats have claimed .prj over the years, so two files with the same extension aren't necessarily the same kind of thing.
How to open a .prj file
- Try LibreOffice (free, Windows/Mac/Linux) — it opens an enormous range of current and historic document formats.
- Microsoft Word and Google Docs handle most mainstream document types.
- If nothing opens it, open it in a text editor: many older document formats have readable text inside.
The registry records this extension against ESRI Shapefile Projection (Well-Known Text) Format, 3D Studio (DOS) Project File, so software from that family is the most likely match.
How to convert a .prj file
- Once it opens in LibreOffice or Word, Save As .docx or .pdf to get it into a format you can use anywhere.
The technical record
For archivists, developers and the merely curious: these are the PRONOM registry entries for .prj.
| Format name | Version | MIME type | PUID |
|---|---|---|---|
| ESRI Shapefile Projection (Well-Known Text) Format | — | — | fmt/320 |
| 3D Studio (DOS) Project File | — | — | fmt/1831 |