Double Hyphen in XML Comment – Fix Invalid -- Comment Syntax

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XML comment content cannot contain the double-hyphen sequence --, even when the final --> terminator is present.

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XML comment syntax

How to fix a double hyphen inside an XML comment

The sample comment is closed, but its content contains -- before the terminator. XML reserves the double-hyphen sequence for comment syntax and does not allow it inside comment text. This tool is free to use. No account or payment is required.

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What you can do here

  • XML well-formedness validation
  • Broken XML example preloaded
  • Corrected XML comparison
  • .xml file import
  • Browser parser feedback
  • Browser-local processing

Steps

  1. Find the comment nearest the parser error.
  2. Search the comment body for any -- sequence before the final -->.
  3. Replace or separate the hyphens while preserving the intended note, then validate again.

A closing --> does not make every comment valid

XML comment grammar also constrains the content between <!-- and -->. An internal -- sequence violates that grammar even when the parser can see an apparent closing delimiter later.

Generated comments need sanitization too

If application data is inserted into XML comments, sanitize or avoid comment serialization for values that can contain arbitrary hyphen sequences.

Invalid double hyphen in XML comment

Replace the internal -- sequence with comment-safe text.

Invalid XML

<root><!-- bad -- comment --></root>

Corrected XML

<root><!-- bad - comment --></root>

Common questions

Frequently asked questions

Can XML comments contain -- inside the comment text?

No. XML comment content cannot contain a double-hyphen sequence.

Is <!-- note --> a valid XML comment?

Yes, provided the comment text itself contains no forbidden -- sequence.

Can XML comments span multiple lines?

Yes, as long as their content and delimiters remain valid.

Recommended next steps

Unclosed XML CommentClose XML comments with --> before the document continues.Unclosed XML CDATA SectionClose <![CDATA[ sections with ]]> before normal XML markup resumes.XML Validator Online – Check XML SyntaxPaste any XML document and check well-formedness locally in your browser.

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