HTML Conformance

Lanexio Parser’s HTML parser implements the full WHATWG HTML parsing algorithm. This page summarizes the conformance status as of v1.0.

html5lib test suite results

Category	Tests	Passed	Skipped	Failed
Tree construction	5,207	5,199	8	0
Tokenizer	2,766	2,766	0	0

All 5,199 tree-construction tests pass. 8 tests are skipped because they require JavaScript execution (#script-on tests). There are zero failures.

All 2,766 tokenizer tests pass.

The full test results are in docs/HTML5_COVERAGE.md in the repository.

Insertion modes

All 23 HTML5 insertion modes are implemented:

Mode	Status
Initial	Implemented
Before HTML	Implemented
Before Head	Implemented
In Head	Implemented
In Head Noscript	Implemented
After Head	Implemented
In Body	Implemented
Text	Implemented
In Table	Implemented
In Table Text	Implemented
In Caption	Implemented
In Column Group	Implemented
In Table Body	Implemented
In Row	Implemented
In Cell	Implemented
In Select	Implemented
In Select In Table	Implemented
In Template	Implemented
After Body	Implemented
In Frameset	Implemented
After Frameset	Implemented
After After Body	Implemented
After After Frameset	Implemented

Complex features

Feature	Status
Adoption agency algorithm	Implemented
Foster parenting	Implemented
Foreign content (SVG, MathML)	Implemented
Scripting-disabled <noscript>	Implemented
<template> element	Implemented
Quirks mode detection	Implemented
Fragment parsing	Implemented

The 8 skipped tests

The 8 skipped tree-construction tests all require running JavaScript (#script-on). They test behavior that depends on document.write() or document.cookie being called during parsing. Lanexio Parser is a static parser and does not execute scripts.

This is not a conformance gap for any practical HTML parsing use case. No static HTML parser implements #script-on behavior.

Spec reference

WHATWG HTML Living Standard § 13.2 (Parsing)
RAG: html_docs::parsing-main@whatwg-2026-03-01

html5lib tests: https://github.com/html5lib/html5lib-tests