XML Formatter / Validator

The XML Formatter / Validator pretty-prints compact XML into readable, indented markup, or checks whether an XML document is well-formed and reports exactly where it breaks. It's the XML equivalent of a JSON formatter, for the file format still underneath countless config files, SOAP APIs, RSS/Atom feeds, Android layouts and enterprise data exchanges.

Formatting is useful whenever XML arrives compacted onto one line — an API response, a minified config, or a feed pulled from a script — and needs indentation restored to actually review its structure. Validation is useful before that XML gets consumed by something stricter than a browser: confirming a hand-edited config file has matching tags before deploying it, or checking that generated XML from a script is well-formed before it's sent to an API that will reject anything malformed.

Formatting works by tokenizing on tag boundaries and indenting by nesting depth — a lightweight, dependency-light approach rather than a full DOM parse-and-rebuild, which means mixed content on a single line (like `<p>Hello <b>world</b>!</p>`) is kept together rather than split awkwardly across lines. Validation uses a dedicated XML parser to check well-formedness — matching tags, valid attribute syntax, a single root element — and reports the exact line and column of the first error found, the same class of check an XML parser in any programming language would perform before accepting the document.

One limitation worth knowing: because formatting works by splitting on `><` boundaries rather than fully parsing the document, a CDATA section that itself contains literal `><` sequences can format unexpectedly — if that happens, validate first to confirm the XML is well-formed, then review the formatted CDATA content manually. For everyday structured XML — nested elements, attributes, simple text content — both modes handle the common cases cleanly and run entirely in your browser.