XML Formatter

XML represents data as nested elements with attributes and text content, and this formatter re-indents that nesting so the document's structure is visible at a glance. It uses the browser's built-in DOMParser to actually parse the document into a DOM tree — rather than just inserting line breaks with regex — then walks that tree recursively, printing self-closing tags for empty elements, single-line tags for elements containing only text, and nested indented blocks for elements with element children.

Because parsing goes through DOMParser, the formatter also validates well-formedness as a side effect: XML requires every tag to be properly closed and nested (unlike HTML, which tolerates some sloppiness), so a missing closing tag or mismatched nesting produces a clear parse error instead of a best-effort guess at formatting. Text nodes that are pure whitespace between elements are trimmed away, so indentation is rebuilt cleanly rather than preserved from the original formatting.

This is useful for reading a minified XML API response, a config file, or an RSS/Atom feed that arrived as one dense line, and for catching structural mistakes like an unclosed tag before they cause problems downstream.

XML must be well-formed: one root element, properly nested tags, matching case, quoted attributes and escaped special characters (& < >). The tool uses the browser's DOMParser, so malformed documents are rejected rather than guessed at.

Whitespace can be meaningful in XML. Re-indenting is safe for data documents, but it can alter mixed content such as text interleaved with tags, so review the output for markup-heavy documents.