cssutils
A CSS Cascading Style Sheets library for Python
Decision gist · record as of 2026-08-14
Yes, if you need to parse, validate, or programmatically modify CSS as structured data. Install friction is low, maintenance is active, and there are no known security vulnerabilities. The copyleft license (LGPL-3.0-or-later) requires attention if you plan proprietary distribution. Not suitable for rendering or for thread-concurrent use.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Requires Python >=3.10.
- cssutils is known to be thread unsafe.
- Low friction install with only two runtime dependencies (more_itertools, encutils).
License · maintenance · safety
LGPL-3.0-or-later (copyleft) — Licensed under LGPL-3.0-or-later (copyleft). Derivative works and modifications must be distributed under compatible terms; proprietary use requires careful license review.
last release 2026-04-27 (109 days) · last repo commit 2026-04-29 · 92 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 9,443,090 downloads/mo, #1,533 on PyPI
Alternatives
Verify before relying
import cssutils
css = 'a { color: red; }'
sheet = cssutils.parseString(css)
for rule in sheet:
if rule.type == rule.STYLE_RULE:
rule.style['color'] = 'blue'
print(sheet.cssText)- Whether the package handles modern CSS features beyond CSS 2.1 and CSS 3 (e.g., CSS Grid, Flexbox, custom properties edge cases).
- Performance characteristics when parsing large stylesheets or many rules in sequence.
- Specific validation strictness for CSS properties and whether it can be configured.
What it is and what it does
cssutils is a CSS parser and DOM builder for Python that reads CSS stylesheets into a structured object model you can inspect and modify programmatically. It implements the W3C DOM Level 2 Style specification and supports CSS 2.1 and parts of CSS 3, including namespaces, media queries, page rules, and custom properties. The package does not render CSS—it is purely for parsing, validation, and serialization.
You use it to load a CSS string or file, walk through rules and properties, modify values or priorities, add or remove rules, and serialize the result back to text. It depends on more_itertools and encutils for utility functions. The library is mature (first released in 2007) and actively maintained, though it is not thread-safe and requires Python 3.10 or later.
Use it for
- Programmatically modify CSS stylesheets in build pipelines or code generation tools.
- Validate CSS syntax and property values before deployment or in linting workflows.
- Extract and analyze CSS rules, selectors, and properties from stylesheets for auditing or transformation.
- Build CSS dynamically by constructing rules and properties in code and serializing them to text.
- Parse CSS from HTML documents or external sources and manipulate them as structured data.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes, if you need to parse, validate, or programmatically modify CSS as structured data.
Install friction is low, maintenance is active, and there are no known security vulnerabilities. The copyleft license (LGPL-3.0-or-later) requires attention if you plan proprietary distribution. Not suitable for rendering or for thread-concurrent use.
Install
cssutils on PyPI
Before you install
Low friction install with only two runtime dependencies (more_itertools, encutils). Active maintenance with a recent release; last commit 2026-04-29. Marked as Production/Stable.
Requires Python >=3.10. cssutils is known to be thread unsafe.
License in practice
Licensed under LGPL-3.0-or-later (copyleft). Derivative works and modifications must be distributed under compatible terms; proprietary use requires careful license review.
Quickstart
import cssutils
css = 'a { color: red; }'
sheet = cssutils.parseString(css)
for rule in sheet:
if rule.type == rule.STYLE_RULE:
rule.style['color'] = 'blue'
print(sheet.cssText)Verify before relying
- Whether the package handles modern CSS features beyond CSS 2.1 and CSS 3 (e.g., CSS Grid, Flexbox, custom properties edge cases).
- Performance characteristics when parsing large stylesheets or many rules in sequence.
- Specific validation strictness for CSS properties and whether it can be configured.
Package facts
| License | LGPL-3.0-or-later copyleft |
| Python support | Supports the current Python release >=3.10 |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | 2 packagesmore_itertoolsencutils |
| Maintenance | Actively maintained 109 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 9,443,090 / month, #1,533 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 5 - Production/StableIntended Audience :: DevelopersProgramming Language :: Python :: 3Programming Language :: Python :: 3 :: OnlyTopic :: InternetTopic :: Software Development :: Libraries :: Python ModulesTopic :: Text Processing :: Markup :: HTML |
Evidence: cssutils-2.15.0-py3-none-any.whl
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