How to open .UO files on iOS
To open .UO files on iOS, in the Files app, try Quick Look; if it can’t preview it, share/open it in a plain-text or code editor app that supports XML (if installed).
Step-by-step instructions
- In the Files app, try Quick Look; if it can’t preview it, share/open it in a plain-text or code editor app that supports XML (if installed).
- If you need full inspection or editing, transfer the file to a desktop system and open it with an XML-capable editor.
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.