What is the PNF file format?
A .pnf file is a Windows system file generated automatically alongside a same-named .inf driver setup file. The name stands for Precompiled INF - Windows creates a .pnf the first time it processes an .inf, storing a binary, pre-parsed version of that file's contents.
PNF files store driver and setup information in binary format, compiled from the source .inf data. For device installation, Windows uses this precompiled version rather than re-parsing the plain-text .inf from scratch each time, which speeds up driver processing. A .pnf is always found beside its matching .inf - for example, oem5.inf has a corresponding oem5.pnf in the same %SystemRoot%\inf\ folder.
PNF files are generated by the system automatically from their companion .inf, so removing them has no adverse consequences for system stability. Windows will regenerate a .pnf the next time the corresponding .inf is processed. Deleting accumulated .pnf files can recover a small amount of disk space, particularly on systems that have had many drivers installed over time.
The binary structure of a .pnf is a Windows-internal format and is not meant to be opened or edited directly. If a .pnf becomes corrupt or stale, Windows simply recreates it from the source .inf.
Security & safety
RISK: LOWA .pnf is a read-only Windows-internal binary cache and carries no active code. It cannot be executed; it is only read by Windows Setup/PnP during driver processing. Deleting a .pnf is safe - Windows regenerates it. The caution here is: do NOT bulk-delete .inf/.pnf pairs from C:\Windows\inf via a cleaner or antivirus without understanding what they are, since the .inf files themselves are needed to reinstall or roll back drivers. The .pnf files are disposable; the paired .inf files are not.
Format details
in a nutshellPrograms that open PNF files
Windows2 apps
Microsoft Windows (auto-generated, no user interaction needed)
Built-in You do not open a .pnf yourself - Windows reads it automatically when processing the matching .inf. If you need to inspect the underlying driver setup script, open the same-named .inf in Notepad or Notepad++.
Notepad++ (for reading the companion .inf instead)
Open-source Open the same-named .inf (not the .pnf) in Notepad++ to read the driver setup script as text. The .pnf itself is binary and not human-readable. Technical details
deep spec| Format | Proprietary binary (Windows-internal INF cache; not a public spec) |
| Byte order | Little-endian |
| File header | First two bytes are 01 03 (minor=1, major=3) on Windows Vista through 8.1; earlier layout on Windows 98/XP |
| Typical file size | 4 KB - 200 KB (mirrors the complexity of the source .inf) |
| Paired file | Always sits beside a same-named .inf (e.g. oem5.pnf ↔ oem5.inf) in the same folder |
| Default location | %SystemRoot%\inf\ or the driver staging store (DriverStore) |
| Internal fields | Version bytes, offsets, then pre-parsed INF section/directive tables; named fields include OsLoaderPath, InfName, SourcePath and WinDirPath |
| WinDirPath offset | 0x58 on Windows 98/XP; moved to 0x68 on Windows Vista and later |
| Error handling | A missing or corrupt .pnf causes Windows to regenerate it from the source .inf automatically |
| Operating system | Windows (all versions from Windows 95/NT onward) |
| Released | Windows 95/NT era (generated automatically when an .inf is first processed by Windows Setup) |
| Latest version | N/A (format evolves with Windows; version bytes 01 03 in header on Vista-8.1; not user-visible) |
PNF conversions
Community Q&A
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