Tinker Tools

XML Formatter Online

Format, minify, and validate XML instantly. All processing is done locally in your browser—your data never leaves your device.

Input XML0 chars
Output

How it works

1. Paste Your XML

Paste your raw or minified XML into the input panel. The tool accepts any valid XML document including those with namespaces and declarations.

Local Processing

2. Choose Action

Select your indentation style and click Format to pretty-print, Minify to compress, or Validate to check for errors in your XML structure.

Instant Results

3. Copy Output

Review the formatted or minified output and copy it to your clipboard with one click. Validation results appear as inline messages.

One-Click Copy

What is XML Formatting?

XML — Extensible Markup Language — is a markup language designed to store and transport data in a format that is both human-readable and machine-parseable. Defined by the W3C, XML uses a tag-based syntax where every piece of data is wrapped in opening and closing tags, and elements can nest inside each other to any depth. You see XML in SOAP web services, RSS and Atom feeds, SVG graphics, Android layout files, Maven build configurations, Microsoft Office document internals (OOXML), and countless enterprise integration formats like HL7 in healthcare and FIX in finance. Despite JSON taking over much of the web API space, XML remains deeply embedded in enterprise systems and is not going away anytime soon.

An XML formatter takes raw or minified XML and restructures it with proper indentation, line breaks, and consistent spacing. Minified XML — a single line with no whitespace between tags — is common in production because it reduces payload size. But reading a 10,000-character XML document on one line is impossible. A formatter transforms that wall of angle brackets into a readable tree structure where you can see parent-child relationships at a glance. Good formatters also validate well-formedness while they work, catching missing closing tags, mismatched tag names, and illegal characters before you waste time debugging downstream errors.

XML formatting and XML validation are related but distinct operations. Formatting addresses visual presentation — indentation, line breaks, attribute alignment. Well-formedness checking verifies that the document follows XML syntax rules: every opening tag has a matching closing tag, attribute values are quoted, element names do not start with numbers, and special characters are properly escaped. Schema validation goes a step further, checking that the document conforms to a specific structure defined in a DTD or XSD — the right elements in the right order with the right data types. A good formatter handles the first two automatically and flags schema issues when you provide a schema file.

Key Features and Benefits

  • Pretty-Printing with Configurable Indentation — The formatter restructures your XML with consistent indentation at every nesting level. Choose between 2-space, 4-space, or tab-based indentation to match your project's conventions. Each child element appears on its own line, indented one level deeper than its parent. Attributes can be kept on the same line as the opening tag or split onto separate lines for elements with many attributes — useful for SVG files and Android layouts where a single element might have ten or more attributes.
  • Minification for Production Deployment — The reverse of pretty-printing: strip all unnecessary whitespace to produce the smallest possible output. Minification removes indentation, line breaks between tags, and trailing spaces. On a typical XML configuration file, this reduces size by 20-40%. For SOAP messages and XML-based API responses transmitted thousands of times per second, that size reduction translates directly into bandwidth savings and faster parse times on the receiving end.
  • Well-Formedness Validation — The formatter checks every XML rule during parsing. Opening and closing tags must match — both in name and case, since XML is case-sensitive. Attribute values must be quoted. The ampersand, less-than, and greater-than characters must be escaped as & < and > when they appear in text content. Only one root element is allowed. These rules are absolute in XML — there is no lenient mode like HTML's error recovery. The formatter reports the exact line and character position of any violation.
  • Namespace-Aware Processing — XML namespaces prevent element name collisions when combining documents from different sources. A namespace declaration like xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" qualifies every element with the soap prefix. The formatter preserves namespace declarations, handles default namespaces, and correctly associates prefixes with their URIs throughout the document. It does not strip or rewrite namespace prefixes unless you explicitly ask for namespace normalization.
  • CDATA Section Preservation — CDATA sections — delimited by <![CDATA[ and ]]> — contain text that should not be parsed as XML. They are commonly used to embed HTML snippets, JavaScript code, or SQL queries inside XML documents without escaping every special character. The formatter preserves CDATA sections exactly as they appear, without indenting their contents or altering their whitespace. This is critical because CDATA content is often whitespace-sensitive code where indentation changes would break functionality.
  • Client-Side Processing — All formatting, validation, and minification happens in your browser. Your XML data — which might contain proprietary schemas, customer data, or internal API definitions — stays on your machine. The parser uses the DOMParser API built into every modern browser, which implements a full XML parser capable of handling documents up to several megabytes. No server uploads, no third-party dependencies, no data exposure risks.

How to Format XML Online

  1. 1

    Paste or Upload Your XML

    Drop your raw XML into the input area. This can be a minified SOAP response, an RSS feed, an Android layout file, a Maven POM, or any other XML document. You can paste directly or drag a .xml file onto the input. The tool accepts documents up to several megabytes — large config files and data exports are handled without issues. If your XML is embedded inside another format — like a CDATA block in a JSON response or a string literal in a programming language — extract just the XML portion first.

  2. 2

    Select Formatting Options

    Choose your indentation style: 2 spaces, 4 spaces, or tabs. Decide whether attributes should stay on the opening tag line or wrap to separate lines. For documents with processing instructions (like <?xml version="1.0"?>) and DOCTYPE declarations, the formatter preserves them at the top of the document. If you want minified output instead, toggle the minify option — this strips all non-essential whitespace and produces a single-line result.

  3. 3

    Run the Formatter

    Click format. The tool parses your XML using a DOM parser, validates well-formedness during parsing, and then serializes the parsed tree back to text with your chosen indentation. If the input is well-formed, you see the formatted output immediately — color-highlighted with tags, attributes, text content, and comments in different colors. If the input has errors, you get a specific error message with the line number and position. Common errors include mismatched tags, unescaped ampersands in URLs, and unclosed elements.

  4. 4

    Review the Document Structure

    Scan the formatted output to verify the structure matches your expectations. Look at the nesting depth — if elements are deeper than you expected, there might be extra wrapper elements. Check namespace declarations on the root element. Verify that CDATA sections are intact and that processing instructions appear correctly. The color highlighting helps you distinguish between element content, attribute values, comments, and CDATA sections at a glance.

  5. 5

    Copy or Download the Result

    Copy the formatted XML to your clipboard or download it as an .xml file. The output preserves the original XML declaration (including encoding and standalone attributes) and uses the encoding specified in the declaration. If no declaration is present, the output defaults to UTF-8. For minified output, the download produces a compact file ready for deployment. You can also switch between formatted and minified views without re-parsing — the tool keeps the parsed DOM in memory and re-serializes on demand.

Expert Tips for Working with XML

Understand the difference between DTD and XSD validation. A Document Type Definition — DTD — is the older schema language, built into the XML 1.0 specification itself. It defines allowed elements, attributes, and their relationships using a specialized syntax that is not XML. DTDs cannot constrain data types — you cannot say that an age element must contain an integer between 0 and 150. XML Schema Definition — XSD — solves this. Written in XML syntax itself, XSD supports data types, complex type inheritance, regular expression patterns for string values, and fine-grained occurrence constraints. If you are working with SOAP services, the WSDL file references an XSD schema. If you are working with legacy systems, you might encounter DTDs. For new projects, always prefer XSD or the more modern RELAX NG schema language.

Know when to use SAX versus DOM parsing. DOM — Document Object Model — parsing loads the entire XML document into memory as a tree structure. You can navigate up, down, and sideways through the tree, modify nodes, and serialize back to text. This is convenient but memory-hungry: a 100 MB XML file can consume 500 MB or more of RAM as a DOM tree because of the overhead of node objects, attribute maps, and namespace tables. SAX — Simple API for XML — is an event-driven parser that reads the document sequentially and fires callbacks for each opening tag, closing tag, and text node. It uses almost no memory because it does not build a tree. Use DOM for documents under 10 MB that you need to query and modify. Use SAX or its modern successor StAX — Streaming API for XML — for large documents that you only need to read once.

Be careful with whitespace in XML. Unlike JSON, whitespace between XML tags can be significant. An element declared as mixed content — containing both text and child elements — preserves every space and newline between tags. A formatter that adds indentation to mixed-content elements changes the document's meaning. Most formatters handle this correctly for pure data XML where text content appears only in leaf elements. But if you are working with XHTML, DocBook, or any format where mixed content is common, verify that the formatter has a mixed-content mode or at minimum does not alter the whitespace inside text-containing elements. A wrong space in an XHTML document can change how a browser renders text.

Consider the XML versus JSON tradeoff for new projects. XML has features that JSON lacks: namespaces for avoiding name collisions across vocabularies, attributes for metadata that is distinct from element content, schema validation with XSD, and transformation with XSLT. JSON is simpler, smaller, and maps directly to data structures in most programming languages. For web APIs consumed by JavaScript frontends, JSON wins on every practical metric — smaller payloads, faster parsing, simpler code. For document-oriented formats where you need mixed content, metadata attributes, and formal schema validation — think publishing, healthcare, government standards — XML is still the better choice. The decision is not about which is better in the abstract. It is about which one fits your specific requirements, tooling, and ecosystem.

Related Tools

JSON Formatter

Format JSON as an alternative data interchange format

HTML Encoder

Encode special characters in XML content

HTML Minifier

Minify HTML/XHTML documents similarly

XML sits at the intersection of data interchange and document markup, and these related tools cover adjacent needs. When your project uses both XML and JSON — common in systems that bridge SOAP and REST APIs — the JSON formatter handles the other half of your data. The HTML encoder helps when you need to embed special characters inside XML text content or attributes without breaking the parser. And the HTML minifier handles the closely related task of compressing HTML and XHTML documents, which share much of their syntax with XML. Together, these tools cover the full spectrum of markup and data formatting tasks.

Frequently Asked Questions

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