HTML, with a feline vocabulary
CaTML stands for Cat Altered Text Markup Language. It is a lightweight JavaScript compiler and runtime that replaces familiar HTML names with a deliberately cat-themed vocabulary, then translates that vocabulary back into standard semantic HTML.
The joke is part of the design, but the underlying idea is concrete: a small domain-specific language can offer a different authoring surface while still producing output that a normal browser understands. The implementation is described as dependency-free.
A readable translation layer
The vocabulary covers document structure, headings, paragraphs, links, images, buttons, forms and other common elements. A box becomes a div, a purr becomes a paragraph and meow-numbered tags map to heading levels. The project also translates attributes for link destinations, image sources, classes, IDs and interaction handlers.
This keeps the output connected to ordinary web concepts. CaTML is not a replacement browser engine: it is a themed authoring and compilation layer over existing HTML and JavaScript behavior.
Three ways to use it
- Embed CaTML in a script element with the documented text/catml type and load the runtime.
- Write a standalone page using the project's document-level feline tags.
- Use the JavaScript API to compile markup into an HTML string or render it into a DOM element.
An interactive place to experiment
The included playground presents a live preview alongside compiled HTML, making the translation visible as you edit. Built-in examples include a welcome page, an interactive counter, an adoption form and a portfolio, while a vocabulary dialog helps users discover the supported names.
The playground can be opened from the repository's index page in a browser. A Node.js test suite provides a separate way to check the compiler behavior without relying only on visual inspection.
A small language-design experiment
CaTML is a useful curiosity for people interested in parsers, markup transformations and playful developer tools. Its scope is intentionally approachable: explore the examples, compare input with generated HTML and follow the compiler source to see how the mappings work. The repository uses the MIT license. The featured illustration is conceptual artwork rather than a screenshot of the playground.
Explore the repository
Read the source code and project documentation for the latest implementation details and setup instructions. This description is based on the public repository reviewed on October 29, 2026.