GitHub - EmilStenstrom/justhtml: A pure Python HTML5 parser that just works. No C extensions to compile. No system dependencies to install. No complex API to learn.

JustHTML

A pure Python HTML5 parser that just works. No C extensions to compile. No system dependencies to install. No complex API to learn.

📖 Full documentation | 🛝 Try it in the Playground

Why use JustHTML?

Just... Correct ✅ — Spec-perfect HTML5 parsing with browser-grade error recovery — passes the official 9k+ html5lib-tests suite, with 100% line+branch coverage. (Correctness)

JustHTML("<p><b>Hi<i>there</b>!", fragment=True).to_html(pretty=False)
# => <p><b>Hi<i>there</i></b><i>!</i></p>

# Note: fragment=True parses snippets (no <html>/<body> needed)

Just... Python 🐍 — Pure Python, zero dependencies — no C extensions or system libraries, easy to debug, and works anywhere Python runs, including PyPy and Pyodide. (Run in the browser)
```
python -m pip show justhtml | grep -E '^Requires:'
# Requires: [intentionally left blank]
```

Just... Secure 🔒 — Safe-by-default sanitization at construction time — built-in Bleach-style allowlist sanitization on JustHTML(...) (disable with sanitize=False). Can sanitize inline CSS rules. (Sanitization & Security)

JustHTML(
    "<p>Hello<script>alert(1)</script> "
    "<a href=\"javascript:alert(1)\">bad</a> "
    "<a href=\"https://example.com/?a=1&b=2\">ok</a></p>",
    fragment=True,
).to_html()
# => <p>Hello <a>bad</a> <a href="https://example.com/?a=1&amp;b=2">ok</a></p>

Just... Query 🔍 — CSS selectors out of the box — one method (query()), familiar syntax (combinators, groups, pseudo-classes), and plain Python nodes as results. (CSS Selectors)
```
JustHTML(
    "<div><p class=\"x\">Hi</p><p>Bye</p></div>",
    fragment=True,
).query("div p.x")[0].to_html(pretty=False)
# => <p class="x">Hi</p>
```

Just... Transform 🏗️ — Built-in DOM transforms for: drop/unwrap nodes, rewrite attributes, linkify text, and compose safe pipelines. (Transforms)

from justhtml import JustHTML, Linkify, SetAttrs, Unwrap

doc = JustHTML(
    "<p>Hello <span class=\"x\">world</span> example.com</p>",
    transforms=[
        Unwrap("span.x"),
        Linkify(),
        SetAttrs("a", rel="nofollow"),
    ],
    fragment=True,
    safe=False,
)
print(doc.to_html(pretty=False))
# => <p>Hello world <a href="http://example.com" rel="nofollow">example.com</a></p>

Just... Fast Enough ⚡ — Fast for the common case (fastest pure-Python HTML5 parser available); for terabytes, use a C/Rust parser like html5ever. (Benchmarks)
```
/usr/bin/time -f '%e s' bash -lc \
  "curl -Ls https://en.wikipedia.org/wiki/HTML | python -m justhtml - > /dev/null"
# 0.41 s
```

Comparison

Tool	HTML5 parsing [1][2]	Speed	Query API	Sanitizes output	Notes
JustHTML Pure Python	✅ 100%	⚡ Fast	✅ CSS selectors	✅ Built-in (`safe=True`)	Correct, easy to install, and fast enough.
Chromium browser engine	✅ 99%	🚀 Very Fast	—	—	—
WebKit browser engine	✅ 98%	🚀 Very Fast	—	—	—
Firefox browser engine	✅ 97%	🚀 Very Fast	—	—	—
`html5lib` Pure Python	🟡 88%	🐢 Slow	🟡 XPath (lxml)	🔴 Deprecated	Unmaintained. Reference implementation; Correct but quite slow.
`html5_parser` Python wrapper of C-based Gumbo	🟡 84%	🚀 Very Fast	🟡 XPath (lxml)	❌ Needs sanitization	Fast and mostly correct.
`selectolax` Python wrapper of C-based Lexbor	🟡 68%	🚀 Very Fast	✅ CSS selectors	❌ Needs sanitization	Very fast but less compliant.
`html.parser` Python stdlib	🔴 4%	⚡ Fast	❌ None	❌ Needs sanitization	Standard library. Chokes on malformed HTML.
`BeautifulSoup` Pure Python	🔴 4% (default)	🐢 Slow	🟡 Custom API	❌ Needs sanitization	Wraps `html.parser` (default). Can use lxml or html5lib.
`lxml` Python wrapper of C-based libxml2	🔴 1%	🚀 Very Fast	🟡 XPath	❌ Needs sanitization	Fast but not HTML5 compliant. Don't use the old lxml.html.clean module!

[1]: Parser compliance scores are from a strict run of the html5lib-tests tree-construction fixtures (1,743 non-script tests). See docs/correctness.md for details.

[2]: Browser numbers are from justhtml-html5lib-tests-bench on the upstream html5lib-tests/tree-construction corpus (excluding 12 scripting-enabled cases).

Installation

Next: Quickstart Guide, CSS Selectors, Sanitization & Security, or try the Playground.

Requires Python 3.10 or later.

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

If you installed JustHTML (for example with pip install justhtml or pip install -e .), you can use the justhtml command. If you don't have it available, use the equivalent python -m justhtml ... form instead.

# Pretty-print an HTML file
justhtml index.html

# Parse from stdin
curl -s https://example.com | justhtml -

# Select nodes and output text
justhtml index.html --selector "main p" --format text

# Select nodes and output Markdown (subset of GFM)
justhtml index.html --selector "article" --format markdown

# Select nodes and output HTML
justhtml index.html --selector "a" --format html

# Example: extract Markdown from GitHub README HTML
curl -s https://github.com/EmilStenstrom/justhtml/ | justhtml - --selector '.markdown-body' --format markdown | head -n 15

Output:

# JustHTML

[](#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](/EmilStenstrom/justhtml/blob/main/docs/index.md)**

## Why use JustHTML?

- **Just... Correct ✅** — Spec-perfect HTML5 parsing with browser-grade error recovery — passes the official 9k+ [html5lib-tests](https://github.com/html5lib/html5lib-tests) suite, with 100% line+branch coverage. ([Correctness](/EmilStenstrom/justhtml/blob/main/docs/correctness.md))
- **Just... Python 🐍** — Pure Python, zero dependencies — no C extensions or system libraries, easy to debug, and works anywhere Python runs (including PyPy and Pyodide). ([Quickstart](/EmilStenstrom/justhtml/blob/main/docs/quickstart.md))
- **Just... Secure 🔒** — Safe-by-default sanitization at construction time — built-in Bleach-style allowlist sanitization on `JustHTML(...)` (disable with `safe=False`), plus URL/CSS rules. ([Sanitization & Security](/EmilStenstrom/justhtml/blob/main/docs/sanitization.md))

Security

For security policy and vulnerability reporting, please see SECURITY.md.

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.

Correctness and conformance work is heavily guided by the html5lib ecosystem and especially the official html5lib-tests fixtures used across implementations.

The sanitization API and threat-model expectations are informed by established Python sanitizers like Bleach and nh3.

The CSS selector query API is inspired by the ergonomics of lxml.cssselect.

License

MIT. Free to use both for commercial and non-commercial use.