XML Formatter: format and validate XML online

XML (eXtensible Markup Language) is a markup format for structured data. XML is used in RSS feeds, Sitemaps, configuration files, SOAP APIs, and many enterprise systems. Formatting makes XML readable, while validation checks its syntax.

To format XML, use XML Formatter on reChecker.

What is XML

XML is a text format for representing data as a tree of elements. Unlike HTML, XML strictly follows a hierarchy and requires all tags to be closed.

Structure of an XML document:

CodeXML

<?xml version="1.0" encoding="UTF-8"?>
<root>
  <element attribute="value">
    <child>Text content</child>
  </element>
</root>

Components:

Declaration — <?xml version="1.0" encoding="UTF-8"?> (optional, but recommended)
Root element — a single top-level element (required)
Elements — tags with opening and closing parts
Attributes — ключ="значение" pairs inside the opening tag
Text — content between tags

Why format XML

Minified XML is a single line with no indentation:

CodeXML

<?xml version="1.0"?><rss version="2.0"><channel><title>My Blog</title><link>https://example.com</link><item><title>Post 1</title></item></channel></rss>

The same XML after formatting:

CodeXML

<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0">
  <channel>
    <title>My Blog</title>
    <link>https://example.com</link>
    <item>
      <title>Post 1</title>
    </item>
  </channel>
</rss>

Formatting is useful for:

Debugging — the structure is visible, making errors easier to find
Editing — it is easier to add or remove an element
Code review — readable XML is easier to review
Documentation — XML examples in documentation should be readable

Uses of XML

RSS / Atom

Content syndication formats. News aggregators, Telegram bots, and other services read RSS to get updates from blogs and websites.

CodeXML

<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0">
  <channel>
    <title>reChecker Blog</title>
    <link>https://rechecker.ru/blog</link>
    <description>Статьи об SEO и веб-инструментах</description>
    <item>
      <title>SQL Formatter: форматирование запросов</title>
      <link>https://rechecker.ru/blog/sql-formatter-guide</link>
      <pubDate>Fri, 14 Mar 2026 10:00:00 +0300</pubDate>
    </item>
  </channel>
</rss>

Sitemap.xml

Google and Yandex use sitemap.xml to discover website pages. It is an XML file containing a list of URLs and metadata.

CodeXML

<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <url>
    <loc>https://rechecker.ru/</loc>
    <changefreq>daily</changefreq>
    <priority>1.0</priority>
  </url>
  <url>
    <loc>https://rechecker.ru/services/sql-formatter</loc>
    <changefreq>weekly</changefreq>
    <priority>0.8</priority>
  </url>
</urlset>

To validate and check a Sitemap: Sitemap checker.

Configuration files

XML is used in Maven configurations (pom.xml), Android (AndroidManifest.xml), Spring, JUnit, Log4j, and many other Java/Enterprise systems.

CodeXML

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
  <database>
    <host>localhost</host>
    <port>5432</port>
    <name>myapp</name>
    <pool>
      <min>5</min>
      <max>20</max>
    </pool>
  </database>
  <cache>
    <ttl>3600</ttl>
    <enabled>true</enabled>
  </cache>
</configuration>

SOAP API

SOAP (Simple Object Access Protocol) is an XML-based protocol for web services. It predates REST but is widely used in banking and ERP systems.

CodeXML

<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Body>
    <GetUserRequest>
      <UserId>42</UserId>
    </GetUserRequest>
  </soap:Body>
</soap:Envelope>

Rules for valid XML

1. One root element

An XML document must have exactly one root element:

CodeXML

<!-- Неверно — два корневых элемента -->
<users>...</users>
<orders>...</orders>

<!-- Верно -->
<data>
  <users>...</users>
  <orders>...</orders>
</data>

2. All tags must be closed

Unlike HTML, XML does not have “unclosed” tags:

CodeXML

<!-- Неверно -->
<br>
<img src="logo.png">

<!-- Верно -->
<br/>
<img src="logo.png"/>

3. Attributes must be quoted

Attribute values must be enclosed in single or double quotes:

CodeXML

<!-- Неверно -->
<item id=42 active=true>

<!-- Верно -->
<item id="42" active="true">

4. Escaping special characters

The characters <, >, &, ", ' in text and attributes must be escaped:

Character	Replacement
`<`	`<`
`>`	`>`
`&`	`&`
`"`	`"`
`'`	`'`

CodeXML

<!-- Неверно -->
<title>Книга: "Война & Мир" </title>

<!-- Верно -->
<title>Книга: &quot;Война &amp; Мир&quot;</title>

5. Tag name case matters

XML is case-sensitive: <User> and <user> are different tags.

CodeXML

<!-- Ошибка: открыт как User, закрыт как user -->
<User>Ivan</user>

<!-- Верно -->
<User>Ivan</User>

6. Namespaces

XML supports namespaces to avoid name conflicts when combining documents:

CodeXML

<root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <url>...</url>
</root>

Common XML errors

Error	Cause	Fix
`XML or text declaration not at start`	Spaces or a BOM before `<?xml`	Remove spaces at the beginning of the file
`Entity 'amp' not defined`	Unescaped `&`	Replace `&` with `&`
`Mismatched tag`	Tag opened as `<Item>` and closed as `</item>`	Check the case
`Attribute without quotes`	`<tag id=5>`	Add quotes: `id="5"`
`Multiple root elements`	Multiple top-level elements	Wrap them in a single root element

XML vs. JSON

Property	XML	JSON
Readability	More verbose, but structured	More compact
Attributes	Embedded in the tag	Only through nested objects
Comments	Supported	Not supported
Size	Larger due to tags	Smaller
Data types	Everything is a string	Numbers, booleans, null
Uses	RSS, Sitemap, SOAP, configs	REST APIs, web

XML tools

Online

XML Formatter on reChecker — formatting, minification, and validation. Everything runs in the browser; data is not sent to a server.

VS Code

The XML extension (Red Hat) adds highlighting, validation, and formatting. Shift+Alt+F — format the file.

Command line

CodeShell

# xmllint (Linux/macOS)
xmllint --format input.xml > output.xml

# xmllint с валидацией
xmllint --valid input.xml

# Python
python3 -c "import sys,xml.dom.minidom; print(xml.dom.minidom.parse(sys.argv[1]).toprettyxml())" input.xml

Node.js

CodeJavaScript

import { XMLParser, XMLBuilder } from 'fast-xml-parser';

const parser = new XMLParser({ ignoreAttributes: false });
const json = parser.parse(xmlString);

const builder = new XMLBuilder({ format: true });
const formatted = builder.build(json);

Conclusion

XML remains a relevant format for RSS, Sitemaps, SOAP, and configuration files. Formatting makes XML readable, while validation helps detect syntax errors before the file is applied. Use XML Formatter to work with XML quickly in your browser.

To format XML, use XML Formatter on reChecker.

What is XML

XML is a text format for representing data as a tree of elements. Unlike HTML, XML strictly follows a hierarchy and requires all tags to be closed.

Structure of an XML document:

CodeXML

<?xml version="1.0" encoding="UTF-8"?>
<root>
  <element attribute="value">
    <child>Text content</child>
  </element>
</root>

Components:

Declaration — <?xml version="1.0" encoding="UTF-8"?> (optional, but recommended)
Root element — a single top-level element (required)
Elements — tags with opening and closing parts
Attributes — ключ="значение" pairs inside the opening tag
Text — content between tags

Why format XML

Minified XML is a single line with no indentation:

CodeXML

<?xml version="1.0"?><rss version="2.0"><channel><title>My Blog</title><link>https://example.com</link><item><title>Post 1</title></item></channel></rss>

The same XML after formatting:

CodeXML

<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0">
  <channel>
    <title>My Blog</title>
    <link>https://example.com</link>
    <item>
      <title>Post 1</title>
    </item>
  </channel>
</rss>

Formatting is useful for:

Debugging — the structure is visible, making errors easier to find
Editing — it is easier to add or remove an element
Code review — readable XML is easier to review
Documentation — XML examples in documentation should be readable

Uses of XML

RSS / Atom

Content syndication formats. News aggregators, Telegram bots, and other services read RSS to get updates from blogs and websites.

CodeXML

<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0">
  <channel>
    <title>reChecker Blog</title>
    <link>https://rechecker.ru/blog</link>
    <description>Статьи об SEO и веб-инструментах</description>
    <item>
      <title>SQL Formatter: форматирование запросов</title>
      <link>https://rechecker.ru/blog/sql-formatter-guide</link>
      <pubDate>Fri, 14 Mar 2026 10:00:00 +0300</pubDate>
    </item>
  </channel>
</rss>

Sitemap.xml

Google and Yandex use sitemap.xml to discover website pages. It is an XML file containing a list of URLs and metadata.

CodeXML

<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <url>
    <loc>https://rechecker.ru/</loc>
    <changefreq>daily</changefreq>
    <priority>1.0</priority>
  </url>
  <url>
    <loc>https://rechecker.ru/services/sql-formatter</loc>
    <changefreq>weekly</changefreq>
    <priority>0.8</priority>
  </url>
</urlset>

To validate and check a Sitemap: Sitemap checker.

Configuration files

XML is used in Maven configurations (pom.xml), Android (AndroidManifest.xml), Spring, JUnit, Log4j, and many other Java/Enterprise systems.

CodeXML

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
  <database>
    <host>localhost</host>
    <port>5432</port>
    <name>myapp</name>
    <pool>
      <min>5</min>
      <max>20</max>
    </pool>
  </database>
  <cache>
    <ttl>3600</ttl>
    <enabled>true</enabled>
  </cache>
</configuration>

SOAP API

SOAP (Simple Object Access Protocol) is an XML-based protocol for web services. It predates REST but is widely used in banking and ERP systems.

CodeXML

<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Body>
    <GetUserRequest>
      <UserId>42</UserId>
    </GetUserRequest>
  </soap:Body>
</soap:Envelope>

Rules for valid XML

1. One root element

An XML document must have exactly one root element:

CodeXML

<!-- Неверно — два корневых элемента -->
<users>...</users>
<orders>...</orders>

<!-- Верно -->
<data>
  <users>...</users>
  <orders>...</orders>
</data>

2. All tags must be closed

Unlike HTML, XML does not have “unclosed” tags:

CodeXML

<!-- Неверно -->
<br>
<img src="logo.png">

<!-- Верно -->
<br/>
<img src="logo.png"/>

3. Attributes must be quoted

Attribute values must be enclosed in single or double quotes:

CodeXML

<!-- Неверно -->
<item id=42 active=true>

<!-- Верно -->
<item id="42" active="true">

4. Escaping special characters

The characters <, >, &, ", ' in text and attributes must be escaped:

Character	Replacement
`<`	`<`
`>`	`>`
`&`	`&`
`"`	`"`
`'`	`'`

CodeXML

<!-- Неверно -->
<title>Книга: "Война & Мир" </title>

<!-- Верно -->
<title>Книга: &quot;Война &amp; Мир&quot;</title>

5. Tag name case matters

XML is case-sensitive: <User> and <user> are different tags.

CodeXML

<!-- Ошибка: открыт как User, закрыт как user -->
<User>Ivan</user>

<!-- Верно -->
<User>Ivan</User>

6. Namespaces

XML supports namespaces to avoid name conflicts when combining documents:

CodeXML

<root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <url>...</url>
</root>

Common XML errors

Error	Cause	Fix
`XML or text declaration not at start`	Spaces or a BOM before `<?xml`	Remove spaces at the beginning of the file
`Entity 'amp' not defined`	Unescaped `&`	Replace `&` with `&`
`Mismatched tag`	Tag opened as `<Item>` and closed as `</item>`	Check the case
`Attribute without quotes`	`<tag id=5>`	Add quotes: `id="5"`
`Multiple root elements`	Multiple top-level elements	Wrap them in a single root element

XML vs. JSON

Property	XML	JSON
Readability	More verbose, but structured	More compact
Attributes	Embedded in the tag	Only through nested objects
Comments	Supported	Not supported
Size	Larger due to tags	Smaller
Data types	Everything is a string	Numbers, booleans, null
Uses	RSS, Sitemap, SOAP, configs	REST APIs, web

XML tools

Online

XML Formatter on reChecker — formatting, minification, and validation. Everything runs in the browser; data is not sent to a server.

VS Code

The XML extension (Red Hat) adds highlighting, validation, and formatting. Shift+Alt+F — format the file.

Command line

CodeShell

# xmllint (Linux/macOS)
xmllint --format input.xml > output.xml

# xmllint с валидацией
xmllint --valid input.xml

# Python
python3 -c "import sys,xml.dom.minidom; print(xml.dom.minidom.parse(sys.argv[1]).toprettyxml())" input.xml

Node.js

CodeJavaScript

import { XMLParser, XMLBuilder } from 'fast-xml-parser';

const parser = new XMLParser({ ignoreAttributes: false });
const json = parser.parse(xmlString);

const builder = new XMLBuilder({ format: true });
const formatted = builder.build(json);

What is XML

Why format XML

Uses of XML

RSS / Atom

Sitemap.xml

Configuration files

SOAP API

Rules for valid XML

1. One root element

2. All tags must be closed

3. Attributes must be quoted

4. Escaping special characters

5. Tag name case matters

6. Namespaces

Common XML errors

XML vs. JSON

XML tools

Online

VS Code

Command line

Node.js

Conclusion

Terms by topic

Sitemap: what it is and why you need one

Code minification: what it is and why it matters

Meta tags: what they are and why they matter

Structured data: what it is and how to add it

SQL Formatter: Format queries online—why and how

CSV and JSON: conversion, formats, and working with data

Escape and Unescape: escaping HTML, JSON, JavaScript, and URLs

Check your website

Feedback

What is XML

Why format XML

Uses of XML

RSS / Atom

Sitemap.xml

Configuration files

SOAP API

Rules for valid XML

1. One root element

2. All tags must be closed

3. Attributes must be quoted

4. Escaping special characters

5. Tag name case matters

6. Namespaces

Common XML errors

XML vs. JSON

XML tools

Online

VS Code

Command line

Node.js

Conclusion

Terms by topic

Sitemap: what it is and why you need one

Code minification: what it is and why it matters

Meta tags: what they are and why they matter

Structured data: what it is and how to add it

SQL Formatter: Format queries online—why and how

CSV and JSON: conversion, formats, and working with data

Escape and Unescape: escaping HTML, JSON, JavaScript, and URLs

Check your website