How to open .UO files on Windows
To open .UO files on Windows, right-click the .UO file → Open with → choose a text/XML editor (for example, a code editor) to view the XML.
Step-by-step instructions
- Right-click the .UO file → Open with → choose a text/XML editor (for example, a code editor) to view the XML.
- If it opens as garbled binary, the file may not be UOML; ask the sender what application created it.
- If you need correct association, set the default app for .UO to your chosen XML-capable editor in Windows settings.
Common issues
No app is suggested / 'Windows can’t open this file'
Your system may not have an association for .UO, or it may not recognize it as UOML (XML).
- Open the file from within a text/XML editor (use File → Open) instead of double-clicking.
- If needed, set your editor as the default app for .UO so the OS knows what to use.
The file opens but looks like unreadable characters
A real UOML file should be XML text; unreadable output suggests the file is not UOML, is compressed/encoded, or is corrupted.
- Check the first few lines in a text editor for XML structure (often starts with <?xml ...?> and tags like <...>).
- If it is not XML, confirm with the sender what created it; do not assume it is UOML just because it ends in .uo.
File type is recognized inconsistently on Linux
Linux desktop identification can depend on the freedesktop.org shared MIME database and whether it includes a glob/association for .uo on your system.
- Update your distribution’s shared-mime-info package so it has current MIME mappings.
- If you manage a desktop environment or fleet, add/adjust a MIME mapping so .uo is associated with application/vnd.uoml+xml where appropriate.
Security note
.UO (UOML) files are XML; they generally don’t execute code by themselves, but they can exploit vulnerabilities in XML parsers or viewers—open untrusted files in a well-maintained editor/viewer.