A pure Python HTML5 parser that just works.
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JustHTML
A pure Python HTML5 parser that just works. No C extensions to compile. No system dependencies to install. No complex API to learn.
📖 Read the full documentation here
Why use JustHTML?
1. Just... Correct ✅
It implements the official WHATWG HTML5 specification exactly. If a browser can parse it, JustHTML can parse it. It handles all the complex error-handling rules that browsers use.
- Verified Compliance: Passes all 8,500+ tests in the official html5lib-tests suite (used by browser vendors).
- 100% Coverage: Every line and branch of code is covered by integration tests.
- Fuzz Tested: Has parsed 3 million randomized broken HTML documents to ensure it never crashes or hangs (see benchmarks/fuzz.py).
- Living Standard: It tracks the living standard, not a snapshot from 2012.
2. Just... Python 🐍
JustHTML has zero dependencies. It's pure Python.
- Just Install: No C extensions to compile, no system libraries (like libxml2) required. Works on PyPy, WASM (Pyodide) (yes, it's in the test matrix), and anywhere Python runs.
- No dependency upgrade hassle: Some libraries depend on a large set of libraries, all which require upgrades to avoid security issues.
- Debuggable: It's just Python code. You can step through it with a debugger to understand exactly how your HTML is being parsed.
- Returns plain python objects: Other parsers return lxml or etree trees which means you have another API to learn. JustHTML returns a set of nested objects you can iterate over. Simple.
3. Just... Query 🔍
Find elements with CSS selectors. Just one method to learn - query() - and it uses CSS syntax you already know.
doc.query("div.container > p.intro") # Familiar CSS syntax
doc.query("#main, .sidebar") # Selector groups
doc.query("li:nth-child(2n+1)") # Pseudo-classes
4. Just... Fast Enough ⚡
If you need to parse terabytes of data, use a C or Rust parser (like html5ever). They are 10x-20x faster.
But for most use cases, JustHTML is fast enough. It parses the Wikipedia homepage in ~0.1s. It is the fastest pure-Python HTML5 parser available, outperforming html5lib and BeautifulSoup.
Comparison to other parsers
| Parser | HTML5 Compliance | Pure Python? | Speed | Query API | Notes |
|---|---|---|---|---|---|
| JustHTML | ✅ 100% | ✅ Yes | ⚡ Fast | ✅ CSS selectors | It just works. Correct, easy to install, and fast enough. |
html5lib |
🟡 88% | ✅ Yes | 🐢 Slow | ❌ None | The reference implementation. Very correct but quite slow. |
html5_parser |
🟡 84% | ❌ No | 🚀 Very Fast | 🟡 XPath (lxml) | C-based (Gumbo). Fast and mostly correct. |
selectolax |
🟡 68% | ❌ No | 🚀 Very Fast | ✅ CSS selectors | C-based (Lexbor). Very fast but less compliant. |
BeautifulSoup |
🔴 4% | ✅ Yes | 🐢 Slow | 🟡 Custom API | Wrapper around html.parser. Not spec compliant. |
html.parser |
🔴 4% | ✅ Yes | ⚡ Fast | ❌ None | Standard library. Chokes on malformed HTML. |
lxml |
🔴 1% | ❌ No | 🚀 Very Fast | 🟡 XPath | C-based (libxml2). Fast but not HTML5 compliant. |
Compliance scores from running the html5lib-tests suite (1,743 tree-construction tests). See benchmarks/correctness.py.
Installation
Requires Python 3.10 or later.
pip install justhtml
Quick Example
from justhtml import JustHTML
doc = JustHTML("<html><body><p class='intro'>Hello!</p></body></html>")
# Query with CSS selectors
for p in doc.query("p.intro"):
print(p.name) # "p"
print(p.attrs) # {"class": "intro"}
print(p.to_html()) # <p class="intro">Hello!</p>
See the Quickstart Guide for more examples including tree traversal, streaming, and strict mode.
Command Line
# Pretty-print an HTML file
python -m justhtml index.html
# Parse from stdin
curl -s https://example.com | python -m justhtml -
Contributing
See CONTRIBUTING.md for development setup and guidelines.
Acknowledgments
JustHTML started as a Python port of html5ever, the HTML5 parser from Mozilla's Servo browser engine. While the codebase has since evolved significantly, html5ever's clean architecture and spec-compliant approach were invaluable as a starting point. Thank you to the Servo team for their excellent work.
License
MIT. Free to use both for commercial and non-commercial use.
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