Unescaped ampersand (EntityRef: expecting ';')

What it means

The ampersand is the character that breaks real documents. XML treats & as the opening of an entity reference, so it must be written & whenever it means a literal ampersand.

This is the single most common failure in generated sitemaps and feeds, because URLs with query strings contain ampersands and string interpolation does not escape them. URL-encoding does not help: %26 is for URLs, & is for XML, and a URL inside XML needs both layers respected.

What usually causes it

• An unescaped & in a URL query string: ?a=1&b=2 instead of ?a=1&b=2.
• Company names and titles containing & written literally.
• HTML built by string concatenation and dropped into a feed without escaping.
• Double-escaping fixes applied on top of already-escaped output, then partially reverted.

How to fix it

• Escape the five predefined entities: & < > " '.
• Escape URLs when writing them into XML, even though they are already URL-encoded.
• Wrap HTML bodies in CDATA rather than escaping them character by character.
• Build XML with a serializer; every one of them escapes content for you.

The same error elsewhere

Different parsers, same defect. If you arrived with one of these messages, you are in the right place.

• libxml2 (bare & with no name)

  xmlParseEntityRef: no name

• Xerces (Java)

  The reference to entity "page" must end with the ';' delimiter.

• expat (Python)

  not well-formed (invalid token): line 2, column 40

• .NET System.Xml

  An error occurred while parsing EntityName.