What is the UPD file format?
A .upd file is a text file that contains information about a specific software update. It typically stores the name of the file that holds the update resources, the version number, release date, and a summary of recent changes - essentially a compact changelog that ships alongside an installer or patch.
In its most common form a .upd file is a plain-text document similar to a .txt file or a .log file, and any text editor can open and read it. Some programs, however, use the .upd extension for proprietary binary update packages - firmware images, data payloads, or compressed archives that only the originating application or device updater can apply.
For the ordinary user, a .upd text file is not very important. It fills an informative role and is not needed for the application to run properly. Deleting it will not have any negative consequences for the application's functionality.
Because there is no universal .upd specification, the simplest way to identify a file is to inspect its first bytes: text variants open cleanly in any text editor such as Notepad, while binary variants will appear as unreadable data and should only be handled by the software that produced them.
Security & safety
RISK: LOWA plain-text .upd is just readable notes and carries no executable risk. The cautions are about the binary case: a .upd 'update package' from an untrusted source could be a tampered or fake update - only apply firmware/software updates obtained from the official vendor, and be wary of a file named like "update.upd.exe" that is actually an executable in disguise. When in doubt, open it in a text editor first to see whether it is harmless notes or a binary blob.
Format details
in a nutshellFULL NAMEUpdate Fileaka update info file, update log file
DEVELOPERN/A (generic; written by many installers, applications and devices)since Convention; .upd has long been used as an 'update' suffix by various software
CATEGORYText Files
MIME TYPEtext/plain
TYPEUsually a plain-text update/changelog file; some programs use .upd for binary update payloads
Programs that open UPD files
Windows2 apps
Notepad++ (or Notepad)
Open-source Open the .upd as text to read the update notes/changelog. Notepad++ handles large files and encodings cleanly.
The program that created it (binary update case)
Built-in If the .upd is a binary update package, apply it through the originating program's update/upgrade feature rather than opening it directly. 
macOS1 app
TextEdit
Built-in Open the .upd as plain text (Format > Make Plain Text if needed) to read the changelog. 
Linux1 app
Any text editor (gedit, nano, Kate)
Built-in Open the .upd as text; run file something.upd first if you're unsure whether it's text or a binary payload. Technical details
deep spec| Format type | Plain-text changelog/update notes (dominant case); proprietary binary update payload (minority case depending on vendor) |
| MIME type | text/plain for text variants; application/octet-stream for binary update packages |
| Text encoding | UTF-8 or ASCII for changelog files; binary update payloads use vendor-defined byte encoding |
| File signature | No universal magic bytes; text .upd files begin directly with human-readable update notes; binary variants carry vendor-specific headers |
| Container format | None - plain text in the changelog case; opaque proprietary binary for firmware or data update packages |
| Compression | None for text changelog variants; binary update packages may embed compressed data internally |
| Integrity checking | Not present in text variants; binary update packages may embed checksums or vendor digital signatures |
| Typical file size | 1 KB - 100 KB for a text changelog; can reach tens of MB for binary firmware update payloads |
| Structure | Free-form version number, release date and changelog entries in the text case; opaque binary blob with vendor-defined layout in the update-package case |
| Associated platforms | Windows, macOS, Linux, and embedded/IoT devices (firmware .upd updates) |
| Developer/owner | No single owner - the extension is a convention used by many software installers, applications and device vendors |
| Specification | No universal specification; format and content are defined entirely by the producing application or firmware system |
| Related extensions | .txt, .log, .nfo, .ini, .dat |
| Safe to delete | Yes for text changelog variants - the file is informational only and its absence does not affect application functionality |
| Released | Convention; .upd has long been used as an 'update' suffix by various software |
UPD conversions
Possible
Not possible
Community Q&A
asked by users
Y
Frequently asked questions
What is a .upd file?
Most often it's a plain-text update file - a readme-style note listing what changed in a software release (version history, fixed bugs, new features). Some programs instead use .upd for a proprietary binary update package.
How do I open a .upd file?
Open it in any text editor (Notepad, Notepad++, TextEdit). If it shows readable update notes, that's all it is. If it shows binary garbage, it's a packaged update you apply through the program that created it, not by hand.
Is a .upd file something I need to run or install?
Usually no - a text .upd is just information about an update. Only the binary 'update package' kind is applied, and that's done through the originating program's update feature, not by double-clicking the file.
My .upd file is unreadable / shows strange characters - why?
Then it isn't the plain-text kind; it's a binary update payload (e.g. a firmware or AV-definition update). Apply it via the vendor's updater rather than trying to read it in a text editor.
Can I delete a .upd file?
A text update-notes .upd is safe to delete - it's just informational. A pending binary update package should be left for its program to apply (or re-download from the vendor if needed).
References
1Notepad++ - free text/source editornotepad-plus-plus.org
2Microsoft - how to identify an unknown file type (open as text)support.microsoft.com
