XML to TOML Converter

Example: XML input and real TOML output

The output below was generated by the same conversion code the converter uses, run on this sample when the page was built.

<catalog>
  <book id="bk101">
    <title>Designing Data-Intensive Applications</title>
    <author>Martin Kleppmann</author>
    <year>2017</year>
  </book>
  <book id="bk102">
    <title>The Pragmatic Programmer</title>
    <author>Andrew Hunt</author>
    <year>1999</year>
  </book>
</catalog>

[[catalog.book]]
title = "Designing Data-Intensive Applications"
author = "Martin Kleppmann"
year = 2017
"@_id" = "bk101"

[[catalog.book]]
title = "The Pragmatic Programmer"
author = "Andrew Hunt"
year = 1999
"@_id" = "bk102"

TOML output is 24% smaller than the XML input. The same data is 214 characters as minified JSON and 341 as pretty-printed JSON. Sizes are character counts, not tokens: token counts depend on the model's tokenizer (see the tokenizer comparison).

XML to TOML: what changes

• Reading XML: Attributes are kept with an @_ prefix (id="bk101" becomes "@_id"), repeated child elements become arrays, and numeric text becomes numbers. A single child element becomes an object, not a one-item array, so the shape depends on how many elements appear.
• Writing TOML: TOML requires a top-level table: a root-level array is wrapped as [[data]]. Arrays of objects become [[name]] array-of-tables blocks, and null values are silently dropped because TOML has no null.

Why Convert XML to TOML?

Use TOML for application configuration, especially in Python (pyproject.toml) or Rust (Cargo.toml) projects. It has explicit types and no ambiguity.