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xml-formatter

An XML formatter parses an XML document, validates that tags are well-formed and properly nested, then re-emits the document with consistent indentation, line breaks, and attribute alignment so the structure becomes visually scannable. The ZTools XML Formatter handles documents of any size, supports configurable indentation (2/4 spaces or tab), highlights syntax errors with line numbers, optionally collapses self-closing tags, and provides a tree-view alongside the formatted text so deeply nested structures stay navigable.

Use cases​

Reading minified XML from a SOAP web service​

Paste a one-line SOAP response, get a properly indented document. Saves the squint-and-scroll routine when debugging API integrations or investigating bank/insurance feeds.

Comparing two XML config files​

Format both config files identically, then run a diff. Same structure but different content stands out instantly instead of being hidden in formatting noise.

Cleaning up exported XML data for documentation​

A vendor exports XML in compact form. Format it, paste into your README or wiki — readers can follow the structure without first having to mentally indent it.

Catching malformed XML before deploying​

Mismatched closing tag? Unescaped ampersand inside an attribute? The formatter shows the exact line and reason so you fix it before pushing to production.

How it works​

  1. Paste your XML — Any size. Documents with or without an XML declaration both work.
  2. Pick indentation style — 2 spaces (default), 4 spaces, or tab. Self-closing tags can be preserved or expanded depending on preference.
  3. Parser checks well-formedness — Mismatched tags, unclosed elements, unescaped & < > inside text, malformed CDATA — each is flagged with the exact line and column.
  4. Read the formatted output — Side-by-side preview shows source vs formatted. The tree-view collapses deep nodes for navigation.
  5. Copy or download — One-click copy. Optional download as .xml. Original input is preserved in case you want to re-format with different settings.

Examples​

Input: <root><a><b>x</b></a></root>

Output: <root> <a> <b>x</b> </a> </root>

Input: <note><to>Tom</to><msg>Hi</msg></note>

Output: Pretty-printed XML with each tag on its own line and indentation per level.

Input: <bad><tag></bad>

Output: ERROR at line 1 col 11: unexpected closing tag </bad> — expected </tag>.

Frequently asked questions​

Does formatting change the XML's meaning?

No — pretty-printing only adds whitespace between tags. The semantic content (elements, attributes, text) is identical. Note: text nodes that contain meaningful whitespace (like <pre>-like content) need xml:space="preserve" to survive reformatting.

How is XML different from HTML?

XML is strict: every tag must close, attributes must be quoted, names are case-sensitive. HTML is forgiving — browsers auto-fix many errors. The formatter assumes XML rules; for HTML, use the HTML formatter.

Will it validate against a schema (DTD or XSD)?

No — this tool checks well-formedness only (syntax). For DTD or XSD validation, use an XML validator with schema support; that requires the schema file and is a separate operation.

How does it handle namespaces?

Namespace declarations and prefixes are preserved exactly. Element ordering and attribute ordering are not changed (just indented). Some formatters re-order attributes alphabetically; this one preserves source order.

Can it format very large XML files?

Yes — multi-megabyte documents work in modern browsers, though very deep nesting (10k+ levels) is slow. For massive files, consider a streaming XML parser instead.

Tips​

  • Always pretty-print before diffing — formatting differences hide content differences.
  • Use the tree-view for documents with deep nesting; the flat formatted text gets unwieldy past 5 levels.
  • Watch for unescaped ampersands inside attributes — XML rejects bare &, requires &.
  • Element ordering matters in XML; don't assume A=B just because they have the same children.

Try it now​

The full xml-formatter runs in your browser at https://ztools.zaions.com/xml-formatter — no signup, no upload, no data leaves your device.

Open the tool ↗

Last updated: 2026-05-05 · Author: Ahsan Mahmood · Edit this page on GitHub