YAML to XML Converter

How This YAML to XML Converter Works

This tool first parses your YAML into a structural tree — resolving anchors, aliases, and merge keys along the way — then walks that tree to generate matching XML elements, entirely in your browser with no server round-trip. The interesting part isn't converting one flat mapping (that's a one-to-one field mapping); it's handling arrays, mixed content, attributes, and YAML's reuse features correctly, which is where many simple converters fall short.

What is YAML?

YAML ("YAML Ain't Markup Language") is a human-readable data serialization format built around indentation instead of brackets. Two-space indentation defines mappings (key: value) and sequences (- item) without the curly braces of JSON or the angle brackets of XML — which is exactly why it became the default format for Kubernetes manifests, Docker Compose, GitHub Actions, Ansible playbooks, and countless application config files.

What is XML?

XML (Extensible Markup Language) is a markup-based, self-describing data format built from nested elements wrapped in opening and closing tags, optionally carrying attributes. Unlike YAML, XML has a mature ecosystem of schemas (XSD, DTD), namespaces, XPath, and XSLT — which is why it remains the standard for SOAP web services, enterprise integrations, legacy systems, Office document formats, and many B2B data exchange protocols that predate JSON and YAML.

YAML vs. XML at a Glance

Why Convert YAML to XML?

Config authors write YAML because it's fast to hand-edit — but plenty of downstream systems still speak only XML: SOAP endpoints, older enterprise service buses, XSLT-based transformation pipelines, XML-based CI systems, and B2B partners with XSD-validated contracts. Rather than hand-translating a YAML config into markup, this converter generates it automatically and consistently, and re-validates the result as well-formed XML every time.

YAML Syntax & XML Structure Primer

YAML Building Blocks

Everything in YAML is one of three things: a mapping (unordered key-value pairs), a sequence (an ordered list), or a scalar (a single string, number, boolean, or null). This converter supports the full practical range: nested mappings and sequences to any depth, flow-style {a: 1} / [1, 2] shorthand, single- and double-quoted strings with escapes, literal (|) and folded (>) block scalars with chomping indicators, comments, anchors (&name), aliases (*name), and merge keys (<<).

name: ToolAdda
version: 2.1
active: true
tags: [fast, private, free]
address:
  city: London
  zip: "EC1A 1BB"

XML Building Blocks

XML is built from elements (<tag>...</tag>), which can carry attributes (<tag attr="value">) and nest other elements or text. A well-formed document has exactly one root element, an optional XML declaration at the top, and every tag must be properly closed or self-closing.

<?xml version="1.0" encoding="UTF-8"?>
<root>
  <name>ToolAdda</name>
  <version>2.1</version>
  <active>true</active>
  <tags>
    <item>fast</item>
    <item>private</item>
    <item>free</item>
  </tags>
  <address>
    <city>London</city>
    <zip>EC1A 1BB</zip>
  </address>
</root>

How Nested Objects, Arrays & Attributes Convert

Every conversion follows a small, predictable set of rules — so the generated XML never surprises you once you know them.

Nested Objects

A YAML mapping becomes an XML element containing one child element per key, in the same order. This applies recursively, so a mapping nested six levels deep produces six levels of nested XML elements.

Arrays & the "Array Item Name" Option

A YAML sequence becomes a wrapper element (named after its key) containing one child element per item. The item element's name is configurable: a fixed name like item for every array in the document, or Auto mode, which derives a singular name from the array's own key — tags becomes tag, products becomes product. Arrays of arrays and arrays of objects both nest correctly, and an empty array becomes a single self-closing wrapper so its presence is never lost.

# YAML
tags: [red, green]

# XML (fixed "item")           # XML (Auto mode)
<tags>                          <tags>
  <item>red</item>                <tag>red</tag>
  <item>green</item>              <tag>green</tag>
</tags>                         </tags>

Attributes: the @ Convention

YAML has no native concept of "attribute" — so this converter uses a widely recognized convention (shared with popular XML/JSON bridging libraries): any mapping key prefixed with @ becomes an XML attribute on that element instead of a nested child. The prefix itself is configurable in the options panel.

# YAML
product:
  "@id": "42"
  "@currency": USD
  name: Widget

# XML
<product id="42" currency="USD">
  <name>Widget</name>
</product>

Mixed Content: the #text Convention

To reproduce XML's "mixed content" pattern — an element with both attributes and its own text, like <price currency="USD">29.99</price> — set a mapping key literally named #text (also configurable) alongside your @-prefixed attribute keys.

# YAML
price:
  "@currency": USD
  "#text": "29.99"

# XML
<price currency="USD">29.99</price>

Namespaces

Because XML namespace declarations are just attributes under the hood, adding a key like "@xmlns:ns": "https://example.com/ns" to any mapping produces a correct namespace declaration on that element — no special-cased namespace syntax needed in the YAML itself.

Scalars, Null Values & Type Hints

Strings, numbers, and booleans become element text as-is. A YAML null (null, ~, or an empty value) becomes a self-closing element by default, so a missing value is never confused with the empty string "". Enable Add type-hint attributes to additionally tag numeric and boolean elements with a type="number" / type="boolean" attribute, and null elements with xsi:nil="true".

Anchors, Aliases & Merge Keys

YAML's reuse features let you define a block once and reference it elsewhere — useful for shared defaults across environments. This converter resolves all of them before generating XML, so the output always contains fully expanded data with no &/* syntax left behind.

• Anchor (&name) — marks a node so it can be referenced again later.
• Alias (*name) — reuses the anchored node's value at that point.
• Merge key (<<: *name) — copies another mapping's keys into the current one; explicit keys already present always win over merged ones.

# YAML
defaults: &defaults
  adapter: postgres
  host: localhost
production:
  <<: *defaults
  database: prod_db

# XML
<production>
  <adapter>postgres</adapter>
  <host>localhost</host>
  <database>prod_db</database>
</production>

If an anchor references itself — directly or through a chain of aliases — the converter detects the circular reference and reports it as an error with the line number, instead of freezing your browser tab in an infinite loop.

Real-World Examples: Kubernetes & Docker Compose

Both of these formats are just deeply nested YAML mappings and sequences — no special handling required, they convert with the same rules as everything else on this page.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 3
  template:
    spec:
      containers:
        - name: nginx
          image: nginx:1.25
          ports:
            - containerPort: 80

<!-- becomes -->
<root>
  <apiVersion>apps/v1</apiVersion>
  <kind>Deployment</kind>
  <metadata><name>nginx-deployment</name></metadata>
  <spec>
    <replicas>3</replicas>
    <template><spec><containers><item>
      <name>nginx</name>
      <image>nginx:1.25</image>
      <ports><item><containerPort>80</containerPort></item></ports>
    </item></containers></spec></template>
  </spec>
</root>

services:
  web:
    image: nginx:latest
    ports:
      - "80:80"
    environment:
      - NODE_ENV=production

<!-- becomes -->
<root>
  <services><web>
    <image>nginx:latest</image>
    <ports><item>80:80</item></ports>
    <environment><item>NODE_ENV=production</item></environment>
  </web></services>
</root>

name: Build and Test
on: [push]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - run: npm install
      - run: npm test

<!-- becomes -->
<root>
  <name>Build and Test</name>
  <on><item>push</item></on>
  <jobs><build>
    <runs-on>ubuntu-latest</runs-on>
    <steps>
      <item><run>npm install</run></item>
      <item><run>npm test</run></item>
    </steps>
  </build></jobs>
</root>

Format Comparisons

YAML vs. JSON

XML vs. JSON

YAML vs. TOML vs. INI

ToolAdda vs. Other Online Converters

Common Conversion Issues & Troubleshooting

Common Mistakes

• Mixing tabs and spaces — YAML forbids tabs for indentation; this converter flags them with a warning so you can swap them for spaces.
• Duplicate keys in the same mapping — the last value silently wins in most YAML parsers; this tool warns you with the exact line number instead of letting it pass unnoticed.
• Unterminated quotes — a stray " or ' with no matching close is reported as a parse error with a line number rather than silently producing garbled output.
• Invalid XML element names — YAML keys can contain spaces, symbols, or start with a digit; none of those are legal XML names. With Auto-fix Invalid Names on, they're rewritten automatically and every rename is listed.
• Forgetting the array item name — every array in the document shares one item name by default; switch to Auto mode if you want each array's items named after its own singularized key instead.

Multi-Document YAML

YAML allows multiple documents in one file, separated by ---. XML documents can only ever have a single root element, so this converter takes the first document and shows a warning if additional documents were found — split multi-document files before conversion if you need every document as XML.

Large YAML Files & Performance

Conversion runs synchronously in your browser. For very large inputs (roughly 350KB and above), live conversion pauses automatically and waits for you to click Convert, so typing in the editor stays smooth instead of blocking on every keystroke.

Best Practices & Privacy

Best Practices

1. Decide your attribute convention (@ prefix) up front if the target system expects specific XML attributes rather than nested elements.
2. Use Auto array-item-name mode when converting data with many differently-named arrays, so the XML reads naturally without manual renaming.
3. Keep Sanitize Names on unless you're certain every YAML key is already a valid XML name — check the rename notice after converting.
4. Turn on type-hint attributes if the consuming system needs to distinguish numbers and booleans from plain text without a schema.
5. For very large configs, split multi-document YAML files before pasting them in, since XML supports only one root document at a time.

Privacy & Security

Parsing and XML generation happen entirely inside your browser's JavaScript engine. No YAML or generated XML is ever transmitted to ToolAdda's servers or any third party, which makes this safe to use even with internal configuration files, infrastructure-as-code, or credentials-adjacent data structures (though secrets should still never be pasted into any online tool, including this one).

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