What is the XLB file format?
.xlb is a settings file used by Microsoft Excel. .xlb files contain no spreadsheet data - only custom toolbar settings. Those settings determine toolbar visibility, window position, and the tools included in each toolbar. This format was central to the classic pre-ribbon versions of Excel (Excel 97 through Excel 2003); after Excel 2007 replaced toolbars with the ribbon interface, .xlb files became largely vestigial.
Location of .xlb files
Changes made to toolbar settings are saved as an .xlb file and stored in the user profile folder at %APPDATA%\Microsoft\Excel\. Common file names include Excel.xlb, Excel10.xlb (Excel XP / 2002), and Excel11.xlb (Excel 2003).
Additional information
.xlbfiles allow users to save and share custom toolbar settings with other users or between computers.- Default toolbar settings can be restored by deleting the
.xlbfile from the default directory and restarting Excel, which regenerates a fresh copy. - The format is a proprietary binary blob - unrelated to the OLE2 compound document format used by
.xlsworkbooks - and its internal layout is undocumented. - On macOS, Excel maintains an equivalent toolbar configuration in its application support folder.
Security & safety
RISK: LOWXLB is a passive, auto-generated settings file with no macro/executable content of its own, so it poses no direct malware risk. The only practical caution is data-loss, not security: deleting or replacing the XLB discards your toolbar/menu customizations (Excel rebuilds a default), and copying one between mismatched Excel versions can cause toolbar glitches - back it up first if your customizations matter.
Format details
in a nutshellPrograms that open XLB files
Windows2 apps
Microsoft Excel (indirect)
Paid You don't open the file; Excel reads it automatically on startup. To reset toolbars, close Excel and rename/delete the .xlb so Excel rebuilds a default one.
File Explorer (locate it)
Built-in Browse to %AppData%\Microsoft\Excel to find Excel.xlb (or Excel1x.xlb). Back it up before deleting if you want to keep your toolbar layout. 
macOS1 app
Microsoft Excel (indirect)
Paid Excel manages its own toolbar/preferences files; there is no user workflow to open an .xlb directly. Technical details
deep spec| Developer | Microsoft |
| Format type | Proprietary binary configuration file (command-bar/toolbar layout) |
| MIME type | application/octet-stream |
| Typical file names | Excel.xlb, Excel10.xlb (Excel XP/2002), Excel11.xlb (Excel 2003) |
| Default storage location (Windows) | %APPDATA%\Microsoft\Excel\ |
| Stores | Custom command-bar layout, toolbar visibility, window position, and per-toolbar tool assignments |
| File signature (magic bytes) | None; no public documented signature - identified by file name and location, not byte pattern |
| Primary Excel versions | Excel 97 through Excel 2003 (pre-ribbon era) |
| Superseded by | Excel 2007 ribbon interface; .xlb customizations do not carry over to ribbon-based Excel |
| Container format | Not an OLE2 compound document; a separate private binary blob distinct from .xls workbook format |
| Third-party tool support | None; no public editors, viewers, or converters exist due to the undocumented format |
| Restoring defaults | Delete the .xlb file and restart Excel; Excel regenerates a clean default copy automatically |
| Platform | Windows (primary); macOS equivalent stored in ~/Library/Application Support/Microsoft/Excel/ |
| Typical file size | A few kilobytes; stores only configuration metadata, not workbook data |
| Related file types | .xls (workbooks), .xlam (add-ins), .xla (older add-ins) - all open in Excel but serve different purposes |
| Released | Classic (pre-ribbon) Excel; relevant through Excel 2003, vestigial after |
| Specification | fileinfo.com |
Community Q&A
asked by usersNo questions yet - be the first to ask about XLB files.
