Start tag expected

What it means

The parser found no start tag anywhere. In practice the document is empty, or what arrived is not XML: an HTML error page, a JSON body, or a redirect notice served with an XML content type.

When this appears on a URL that works in a browser, the usual cause is that the server returns different content to a non-browser client — a login wall, a bot check, or a geo redirect.

What usually causes it

• An empty response body, often a 204 or a failed upstream fetch.
• An HTML error or login page returned with an XML media type.
• A JSON response from an endpoint expected to serve XML.
• A gzip-compressed body read without decompressing.
• A file that exists but was never written to.

How to fix it

• Fetch the URL with curl and look at the first bytes of the real body, not the browser's rendering.
• Check the response status and Content-Type before parsing.
• Decompress .gz sitemaps before validation.
• If a bot check is intercepting, allowlist the crawler or fetch server-side.

The same error elsewhere

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

• libxml2 (PHP, lxml, Nokogiri)

  Start tag expected, '<' not found

• Xerces (Java)

  Premature end of file.

• expat (Python)

  no element found: line 1, column 0

• .NET System.Xml

  Root element is missing.