CSS Validator
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HTML, feeds, and XML tools that pair with checking CSS syntax before ship.
Ctrl+Enter (or ⌘+Enter) to validate.
Paste CSS and get syntax feedback with line and column (PostCSS parse on the server). Grammar only — not browser support, cascade guarantees, or whether a property is deprecated.
The CSS Validator helps you check stylesheet syntax before it reaches production. It parses CSS with a grammar-focused approach, making it useful for catching malformed rules, missing braces, invalid property declarations, and other structural issues that can break a stylesheet. Developers, front-end teams, and QA reviewers use it to spot syntax problems early, especially when working with hand-written CSS, generated styles, or code copied from multiple sources. This tool is designed for validation and error reporting, not browser compatibility testing, so it helps you confirm whether the CSS is syntactically valid rather than whether it will render the same in every browser.
This validator analyzes your CSS as a stylesheet syntax problem. It parses the input and checks whether the rules follow expected CSS grammar. If the parser encounters an issue, it can report the approximate line and column where the problem appears, which helps you locate and fix the error quickly.
CSS syntax errors often come from small formatting mistakes that are easy to miss during editing. A validator can help identify these issues before they affect a page or build pipeline.
CSS validation is useful anywhere stylesheets are authored, reviewed, or generated. It supports both manual workflows and automated quality checks.
Even a small syntax error can prevent part of a stylesheet from being parsed correctly. Validation helps teams catch those issues early, reducing time spent debugging layout problems and avoiding broken styles in production. It is especially useful when CSS is maintained by multiple contributors or assembled from different sources.
This tool is focused on CSS grammar parsing. It validates stylesheet syntax and returns parser-level feedback when the input cannot be read as valid CSS. Because it is syntax-oriented, it does not evaluate whether a property is supported in a specific browser, whether a value is deprecated, or whether the CSS produces the intended visual result.
| Validation scope | CSS syntax and rule structure |
| Error reporting | Line and column-based parsing feedback |
| Not included | Browser compatibility checks, rendering tests, or visual inspection |
| Best for | Finding malformed CSS before deployment |
It checks whether your stylesheet is syntactically valid CSS. That includes rule blocks, selectors, declarations, and at-rules. If the parser finds a problem, it can point to the line and column where the error likely occurs, which makes debugging faster than scanning the file manually.
No. This validator focuses on grammar and syntax, not browser support. A stylesheet can be syntactically valid and still behave differently across browsers due to implementation differences, unsupported features, or vendor-specific behavior. For compatibility testing, you would need a separate browser support workflow.
Yes, those are common syntax issues that a CSS parser can often detect. Missing semicolons, unclosed braces, and malformed declarations are among the most frequent causes of parse errors. The validator helps surface these problems so you can correct them before the stylesheet is used in production.
CSS can fail validation because of small syntax issues that are hard to spot visually, such as an extra character, a broken comment, or a value written in the wrong format. Copy-paste mistakes and incomplete edits are also common causes. The line and column output can help narrow down the exact location.
Yes. It is useful for generated CSS from build tools, templates, or automation workflows, as long as the output is plain CSS. Validating generated styles can help catch pipeline issues early, especially when multiple tools transform the stylesheet before it reaches the browser.
No. Valid syntax only means the stylesheet can be parsed correctly. It does not guarantee that the design will render as intended, because layout depends on HTML structure, browser behavior, media conditions, and the interaction of multiple rules. Validation is one quality check, not the full rendering test.
Common errors include missing punctuation, unclosed blocks, invalid property-value pairs, and malformed at-rules like @media. These issues often happen during quick edits, refactors, or merges. A validator is useful because it can identify structural problems before they become harder-to-debug layout issues.
Yes. Large stylesheets are more likely to contain small syntax mistakes that are difficult to find manually. Validation is especially helpful when files are long, modular, or maintained by multiple contributors. Parser feedback can reduce the time needed to isolate the first syntax error.
Not completely. A CSS validator checks syntax validity, while linting tools usually enforce style rules, naming conventions, and best practices. The two are complementary: validation helps ensure the CSS can be parsed, and linting helps improve consistency and maintainability.