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 									<li>
 										<a href="/document-processing/excel/excel-library/net/faqs/how-to-retrieve-data-from-merged-cells-using-xlsio">How to retrieve data from merged cells using XlsIO?</a>
 									</li>
-                 	<li>
+									<li>
 										<a href="/document-processing/excel/excel-library/net/faqs/how-to-convert-inches-to-points-in-syncfusion-xlsio">How to convert inches to points in Syncfusion XlsIO?</a>
-                  </li>
-                  <li>
-                    <a href="/document-processing/excel/excel-library/net/faqs/how-to-preserve-line-breaks-when-saving-excel-as-csv">How to preserve line breaks when saving Excel as CSV?</a>
+									</li>
+									<li>
+										<a href="/document-processing/excel/excel-library/net/faqs/how-to-preserve-line-breaks-when-saving-excel-as-csv">How to preserve line breaks when saving Excel as CSV?</a>
 									</li>
 									<li>
 										<a href="/document-processing/excel/excel-library/net/faqs/why-text-with-double-quotes-gets-enclosed-in-double-quotes-when-saving-as-csv">Why does text with double quotes get enclosed in double quotes when saving as CSV?</a>
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                   <li>
 										<a href="/document-processing/excel/excel-library/net/faqs/how-to-merge-cells-preserving-topleft-value-and-format-in-xlsio">How to merge cells preserving topleft value and format in XlsIO?</a>
 									</li>
+                  <li>
+										<a href="/document-processing/excel/excel-library/net/faqs/which-characters-should-be-avoided-when-naming-worksheets">Which characters should be avoided when naming worksheets?</a>
+									</li>
 								</ul>
 							</li>
 						</ul>
diff --git a/Document-Processing/Excel/Excel-Library/NET/faqs/which-characters-should-be-avoided-when-naming-worksheets.md b/Document-Processing/Excel/Excel-Library/NET/faqs/which-characters-should-be-avoided-when-naming-worksheets.md
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+---
+title: Invalid characters to avoid in worksheet names | Syncfusion
+description: Worksheet names containing '/' or ':' may corrupt workbooks. This FAQ explains the invalid characters to avoid.
+platform: document-processing
+control: XlsIO
+documentation: UG
+---
+
+# Which characters should be avoided when naming worksheets?
+
+Worksheets that include invalid characters such as `:` or `/` in their names can cause workbook corruption when opened in some viewers or when round-tripping between formats. Use XlsIO to validate and sanitize worksheet names before saving.
+
+## Invalid Characters in Worksheet Names
+
+Excel does not allow the following seven characters in worksheet names:
+
+| Character | Symbol | Issue |
+|---|---|---|
+| Colon | `:` | Causes path confusion in some file systems |
+| Backslash | `\` | Used as path separator, causes file system errors |
+| Forward Slash | `/` | Used as directory separator, creates ambiguity |
+| Question Mark | `?` | Wildcard character, causes parsing issues |
+| Asterisk | `*` | Wildcard character, causes file system conflicts |
+| Opening Bracket | `[` | Reserved for special Excel references |
+| Closing Bracket | `]` | Reserved for special Excel references |
+
+## Why These Characters Cause Corruption
+
+When worksheets contain these forbidden characters, the following issues occur:
+
+1. **File Format Issues**: Excel and other spreadsheet applications may fail to parse the workbook correctly
+2. **Round-trip Conversion Errors**: Converting between formats (XLSX to XLS and back) may corrupt the data
+3. **File System Conflicts**: Path separators (`:`, `\`, `/`) conflict with operating system file naming conventions
+4. **External Tool Failures**: Third-party tools and APIs may not be able to read or write the workbook
+5. **Sharing Problems**: Files become incompatible when shared across different platforms or applications
+
+## Best Practices for Worksheet Names
+
+Follow these guidelines when naming worksheets:
+
+- **Use alphanumeric characters** (letters A-Z, a-z, numbers 0-9)
+- **Use safe special characters** (underscore `_`, hyphen `-`, space ` `)
+- **Avoid all seven forbidden characters** listed above
+- **Keep names under 31 characters** (Excel's maximum limit)
+- **Ensure names are not empty** (at least 1 character required)
+- **Make names meaningful** (use clear, descriptive titles like "Sales Data", "Q1_2026", "Report_Jan")