w3c/css-validator

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W3C CSS Validation Service

Stars: 250
Forks: 123
Open beginner issues: 0
Indexed issues: 43

Dominant language: Java
License: No license data
Last GitHub push: Aug 1, 2026
Latest indexed: Sep 20, 2026
Contributing guide: Contributing guide
Code of conduct: Code of conduct
Beginner labels: No beginner labels indexed
PR merge metrics: No merged PRs in 30d

Beginner friendly Everything

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43 open issues indexed

Misleading parse error Open

Difficulty 3/5 1-2 days Newbie friendliness 65/100

w3c/css-validator#520 · 1 comment · Opened Sep 11, 2026
Not recognizing calc result as number, nor recognizing @property Open

Difficulty 4/5 3-5 days Newbie friendliness 55/100

w3c/css-validator#518 · Opened Aug 29, 2026
Usage of field-sizing: content; returns error Open

Difficulty 3/5 1-2 days Newbie friendliness 65/100

w3c/css-validator#514 · Opened Jul 4, 2026
CSS checker enhancement request; output full details of each error’s location, including errors inside @imports Open

enhancement

Difficulty 4/5 3-5 days Newbie friendliness 45/100

w3c/css-validator#491 · Opened Mar 12, 2026
CSS checker request for enhancement; scanning the contents of @imports should be an option Open

enhancement

Difficulty 3/5 1-2 days Newbie friendliness 45/100

w3c/css-validator#490 · Opened Mar 12, 2026
issue with test testsuite/bugs/4469.css Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

w3c/css-validator#487 · 2 comments · Opened Mar 8, 2026
The validator throws an error when nesting CSS. Open

enhancement

Difficulty 3/5 1-2 days Newbie friendliness 52/100

w3c/css-validator#481 · 1 comment · 3 reactions · Opened Feb 26, 2026
CSS `clip-path` w/o `path()` Open

Difficulty 3/5 1-2 days Newbie friendliness 35/100

w3c/css-validator#480 · Opened Feb 18, 2026
False error for SVG-related properties x, y, d, r, rx, ry, cx, cy Open

Difficulty 3/5 1-2 days Newbie friendliness 48/100

w3c/css-validator#477 · Opened Jan 20, 2026
Property does not exist error on container queries Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

w3c/css-validator#474 · Opened Dec 19, 2025
CSS path() gives error when used for clip-path Open

enhancement

Difficulty 3/5 1-2 days Newbie friendliness 35/100

w3c/css-validator#472 · 1 comment · Opened Dec 11, 2025
Property `clip-path:polygon()` with reference box causes warning Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

w3c/css-validator#471 · Opened Dec 11, 2025
Custom protocol reported as invalid Open

Difficulty 3/5 1-2 days Newbie friendliness 50/100

w3c/css-validator#466 · 1 comment · Opened Nov 18, 2025
validation by file upload fails on tomcat 11 (Unable to process parts as no multi-part configuration has been provided) Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

w3c/css-validator#455 · 5 comments · Opened Jul 6, 2025
Exception in `IndexGenerator::generatesIndex` when served as deployed war Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

w3c/css-validator#451 · Opened Jun 27, 2025
LICENSE.md vs COPYRIGHT.html Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/css-validator#447 · Opened Jun 8, 2025
Parse error Open

Difficulty 3/5 1-2 days Newbie friendliness 52/100

w3c/css-validator#445 · 3 comments · Opened May 23, 2025
Support: template element attributes Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

w3c/css-validator#433 · Opened Dec 27, 2024
Nested Style Rule Parse Error Open

Difficulty 3/5 1-2 days Newbie friendliness 55/100

w3c/css-validator#431 · 3 comments · 8 reactions · Opened Oct 19, 2024
Validator returns "Congratulations! No Error Found." for CSS with syntax errors in it Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

w3c/css-validator#429 · Opened Sep 28, 2024
Only validator - no dependencies Open

Difficulty 4/5 3-5 days Newbie friendliness 30/100

w3c/css-validator#428 · Opened Sep 18, 2024
Unrecognized at-rule @container Open

Difficulty 3/5 1-2 days Newbie friendliness 42/100

w3c/css-validator#422 · Opened Jun 10, 2024
Cast exception when validating @font-face rule with CSS level 2 profile Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

w3c/css-validator#416 · Opened Mar 20, 2024
Possible false validation error "Property d doesn't exist." Open

enhancement SVG

w3c/css-validator#403 · 1 comment · 1 assignee · Opened Jun 19, 2023
Incorrect css shows as correct Open

Difficulty 3/5 1-2 days Newbie friendliness 38/100

w3c/css-validator#398 · 1 comment · Opened Apr 8, 2023
image-set property is reported as an error... incorrectly Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

w3c/css-validator#388 · 2 comments · 1 reaction · Opened Nov 17, 2022
Flags `::part(...)` as an Error Open

Difficulty 3/5 1-2 days Newbie friendliness 35/100

w3c/css-validator#384 · Opened Oct 31, 2022
aspect-ratio not working Open

bug

w3c/css-validator#366 · 3 comments · 1 assignee · Opened Apr 29, 2022
No validation error for incorrect CSS Open

Difficulty 3/5 1-2 days Newbie friendliness 42/100

w3c/css-validator#358 · 5 comments · Opened Mar 2, 2022
Not possible to validate styles for error pages Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

w3c/css-validator#238 · 1 comment · Opened May 23, 2019
POST requests not properly handled Open

Difficulty 3/5 1-2 days Newbie friendliness 35/100

w3c/css-validator#227 · Opened Mar 28, 2019
Please ignore non-existing pseudo-class on pseudo-element vendor extension Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 35/100

w3c/css-validator#214 · 1 comment · Opened Dec 4, 2018
Fix output for IO Errors Open

w3c/css-validator#200 · 1 assignee · Opened Jun 25, 2018
Publish new version to Maven Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

w3c/css-validator#193 · 6 comments · Opened Apr 30, 2018
`check/referer` gives confusing results due to more default restrictive referer policies in browsers Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 35/100

w3c/css-validator#191 · 3 comments · Opened Apr 23, 2018
"Validated CSS" is not correct for some @rules Open

Difficulty 3/5 1-2 days Newbie friendliness 35/100

w3c/css-validator#182 · 2 comments · Opened Mar 16, 2018
Implementation of css-masking-1 Open

SVG

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/css-validator#151 · 2 comments · Opened Jan 19, 2018
Change badges' suggestion for HTML5+ Open

enhancement

Difficulty 2/5 1-3 hours Newbie friendliness 48/100

w3c/css-validator#143 · 2 reactions · Opened Jan 6, 2018
Figure out how to avoid adding skippedString that isn’t helpful Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 25/100

w3c/css-validator#139 · Opened Jan 2, 2018
Move HTML documentation under /docs/ Open

Difficulty 3/5 1-2 days Newbie friendliness 25/100

w3c/css-validator#33 · 1 comment · Opened Sep 6, 2015
Run autotests in Travis CI Open

Difficulty 3/5 1-2 days Newbie friendliness 25/100

w3c/css-validator#18 · 1 comment · Opened Sep 1, 2015
Tag a release Open

Difficulty 2/5 1-3 hours Newbie friendliness 45/100

w3c/css-validator#8 · 1 reaction · Opened Aug 11, 2015
Setup GitHub Pages site for the documentation Open

Difficulty 3/5 1-2 days Newbie friendliness 25/100

w3c/css-validator#3 · 4 reactions · Opened Aug 11, 2015

w3c/css-validator

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