XML Formatter and Checker
Format an XML document, catch parser errors and inspect its basic structure. Processing happens locally in the browser.
Run the formatter to see document statistics.
What this XML formatter checks
The browser parses the input as an XML document. A successful parse confirms basic well-formedness, including matching tags and a single document element. The workbench then serializes the DOM with consistent indentation and reports the root element, namespace, element count and attribute count.
What it deliberately does not claim
Well-formedness is not schema validity. An XML document may parse correctly and still violate an XSD, DTD, RELAX NG grammar or Schematron rule set. Use the output as a syntax checkpoint before standards validation.
Formatting changes text, not the governing data model
The formatter reparses and serializes the document, so indentation between elements can change and insignificant whitespace may be normalized. Attribute order is not an XML semantic guarantee, namespace prefixes are aliases for namespace URIs, and a visually tidy result does not prove that downstream canonicalization or digital-signature requirements are preserved. Treat the formatted text as a review copy unless a byte-for-byte or canonical XML workflow has explicitly approved the transformation.
Mixed content needs particular care because whitespace between words and child elements can carry meaning. The formatter preserves DOM text nodes, but a human reviewer should compare representative rendered or processed output before replacing an authoritative mixed-content document. The tool does not fetch external entities, DTD subsets, schema imports or stylesheets.
A practical XML debugging sequence
First reduce the failing message while preserving its declaration, namespace bindings and problematic node. Fix the earliest parser error because later diagnostics may be consequences of the first malformed token. Then run the clean document through the exact XSD, DTD, RELAX NG or Schematron processors used by the receiver. Retain the reduced invalid fixture and its expected error category in source control so the same syntax regression cannot return unnoticed.
For schema design questions, continue with the XSD Pattern Analyzer or read the XML Schema tutorial.
Frequently asked questions
01Does the XML formatter upload my document?
No. Formatting and parsing on this page happen inside the active browser tab. The pasted XML is not sent to an xFront server.
02Does this tool validate XML against an XSD?
No. It checks XML well-formedness and reports parser errors. XSD validation requires a conforming schema processor and may need multiple imported schema documents.
03What is well-formed XML?
Well-formed XML follows the core syntax rules: one document element, correctly nested tags, quoted attributes and valid character usage, among other requirements.
04Will formatting change text values?
The formatter inserts structural whitespace between elements. It does not intentionally rewrite text or attribute values, but whitespace can be significant in some XML vocabularies, so compare sensitive documents before replacing a source file.
05Can the formatter resolve external entities?
No. The browser parser used here does not fetch an external DTD or schema. This avoids hidden network requests but also means external declarations are outside the check.
06Why does the error position vary by browser?
DOMParser error messages are supplied by the browser engine. Wording and exact location reporting can differ between Chromium, Firefox and Safari.
07Does the tool support XML namespaces?
Yes. Namespaced documents can be parsed and formatted. The summary reports the namespace URI of the document element when one is present.
08Can I format very large XML files?
The practical limit depends on browser memory and document complexity. For large production files, a streaming command-line formatter is more predictable.
What to inspect after the document parses
Check the XML declaration against the bytes used to store or transmit the document. A declaration naming UTF-8 does not repair content that was decoded with another character set, and a JavaScript string no longer exposes the original byte-order mark. If the failure involves corrupted characters, reproduce it from the original bytes in the receiving parser rather than relying on pasted text alone.
Review expanded names, not only visible prefixes. Two elements with different prefixes can have the same namespace name, while matching prefixes can denote different URIs in different scopes. Confirm the reported root namespace against the vocabulary contract and inspect unprefixed attributes separately because the default namespace does not apply to them.
Next distinguish syntax cleanup from application change. Reformat a disposable copy, compare parsed structures, and keep the original when signatures, canonicalization, mixed content or whitespace-sensitive applications are involved. For messages entering a pipeline, validate size limits and disable unneeded external resolution in the authoritative parser. A formatter is useful at the first debugging boundary, but secure parsing policy belongs to the consuming system.
Evidence worth retaining
A strong issue report includes the minimized original, the earliest parser diagnostic, the corrected document and the exact production parser or validator version. Note whether the text came from a file, HTTP message, database or already-decoded application string. These details separate an XML grammar problem from a transport encoding, truncation or content-type problem.