What is a .pac file?
A .pac file is a proxy Auto-Configuration file. Its registered MIME type is application/x-ns-proxy-autoconfig, which places it in the application or document family of formats.
Technically it is a specialised form of text/javascript (the .cjs format), so tools that understand that format can often read at least part of it.
PAC is a text-based format: the contents are readable characters, so any text editor can open it, and it compresses well.
PAC file format details
| Extension | .pac |
|---|---|
| Format | Proxy Auto-Configuration file |
| MIME type | application/x-ns-proxy-autoconfig |
| Category | Application or document |
| Text or binary | Text |
| Based on | text/javascript |
| File signature | None fixed |
| Registered with IANA | No |
| Other extensions | None |
How to open PAC files
| Windows | PAC files are plain text, so Notepad opens them: right-click the file, choose Open with, then Notepad. Notepad++ and VS Code are free and show long files more comfortably. |
|---|---|
| Mac | TextEdit opens plain text files. For code or data files, a free editor such as BBEdit or VS Code keeps the formatting intact. |
| iPhone and iPad | Save the file to the Files app and tap it; iOS previews most plain text. Or drop it on the viewer above, which shows the text right in the browser. |
| Android | Most file manager apps open plain text files in a built-in viewer. The viewer above also works in Chrome. |
Can you convert a .pac file?
TapToConvert does not convert PAC files. The usual route is to open the file in the program that made it and use its Export or Save as option.
PAC file FAQ
What is a .pac file?
A .pac file is a proxy Auto-Configuration file, with the MIME type application/x-ns-proxy-autoconfig.
How do I open a .pac file?
With any text editor, such as Notepad on Windows or TextEdit on a Mac, or with the viewer on this page.
Is a .pac file safe to open?
PAC files hold data rather than programs, but any file from an unknown source can be crafted to exploit the software that opens it. Keep that software up to date. The viewer on this page only reads the bytes and never runs anything.
What is the MIME type of .pac?
application/x-ns-proxy-autoconfig. Web servers send this type so browsers know how to handle the file.
Is PAC a text or binary format?
Text. Its contents are readable characters.
File type facts come from the IANA media type registry, the mime-db project and the freedesktop.org shared MIME database.