What Is an XML Formatter and Validator?
This xml formatter online reformats dense or inconsistently indented XML into readable markup, with a choice of indentation width, and can also minify or validate it. XML still backs a huge share of real infrastructure: SOAP APIs, RSS and Atom feeds, Android layout files, Maven POMs, SVG, and countless enterprise configuration files. Use it to format xml online and xml pretty print a minified API response into something readable, or as an xml validator online to catch a broken tag or unescaped character before it reaches a downstream parser.
How XML Formatting and Validation Work
This xml beautifier parses XML into a real document structure before reformatting it, rather than applying regex-based indentation guesses, so the formatted output reflects the document's actual element nesting. When a document is not well-formed, this xml syntax checker reports the specific line and column where parsing broke, for example a missing closing tag or a stray unescaped ampersand, rather than a vague "invalid XML" message that leaves you to search the document by eye.
What Makes XML "Well-Formed"
A well-formed XML document follows the syntax rules of the XML specification: exactly one root element, every opening tag has a matching closing tag or is self-closing, tags are properly nested without overlapping, attribute values are quoted, and special characters like an ampersand are escaped in text content. Every XML document must have exactly one top-level element containing everything else. A document with two sibling elements at the root level is not well-formed, one of the most common mistakes this xml well-formed checker catches immediately.
Reading a Line/Column Syntax Error
When validation fails, the error message includes a line and column number pointing to exactly where the parser stopped. Open the fullscreen view, where line numbers are shown on the left, and go directly to that line rather than scanning the whole document by eye. Common causes at that position include an unclosed tag, an unescaped ampersand, an unquoted attribute value, or a second root-level element where the parser expected only one.
What This Tool Does Not Do
This tool checks that a document is well-formed XML, it does not validate against an XML Schema (XSD) or DTD, so a document can pass this tool's validation while still failing a schema-specific business rule elsewhere. It is also not a dedicated place to minify xml online for storage or transmission alone, that is simply one of its three actions alongside formatting and validation. Nothing pasted here is uploaded; formatting and validation happen entirely in your browser.