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
Section titled “html5lib test suite results”| Category | Tests | Passed | Skipped | Failed |
|---|---|---|---|---|
| Tree construction | 1,778 | 1,778 | 0 | 0 |
| Tokenizer | 2,766 | 2,766 | 0 | 0 |
All 1,778 tree-construction tests pass. There are zero failures and zero skipped tests.
All 2,766 tokenizer tests pass.
The docs/HTML5_COVERAGE.md ledger in the repository is a frozen Phase 1 development baseline (snapshot 2026-05-01) that predates the completion of the tree builder; it does not reflect current results.
Insertion modes
Section titled “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
Section titled “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 |
Spec reference
Section titled “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
Corpus conformance
Section titled “Corpus conformance”On top of the html5lib suite above, pnpm conformance:suite measured this family over the
test_files/html corpus on 2026-10-06 at Lanexio™ Parser version 1.0.0:
| family | valid | invalid | raw | contract-subset | REAL-DEFECT |
|---|---|---|---|---|---|
| html | 12092 | 195 | 98.4% | 100.0% (12092/12092) | 0 |
The raw figure reflects 195 inputs the directory rule labels invalid that the parser accepts; the contract-subset over the 12,092 valid inputs is 100.0%.