Syntax Validation Tools
CSS Validator
Check whether a stylesheet can be parsed as CSS and locate syntax errors before copying rules into a project.
✓ Every tool runs in your browser. We do not upload your input or output.
Keyboard shortcuts
Ctrl/⌘ + Enter: process
Ctrl/⌘ + Shift + F: full screen
Esc: exit full screen
Ctrl/⌘ + F in editor: search
How to use
- Paste a CSS rule or complete stylesheet.
- Run validation and read the reported line and column if parsing fails.
- Correct the source at the highlighted location and run it again.
- Use the CSS Formatter afterward if you also want consistent layout.
Examples
Check a component rule
The parser accepts a well-formed rule; visual behavior still needs browser testing.
.card { display: flex; gap: 1rem; }Valid CSS syntax
Catch parsing mistakes early
A missing brace or malformed declaration can make the rest of a stylesheet harder to reason about. Paste the relevant CSS into the workspace and use the reported location to inspect the nearby rule. The validator shares its parser with the CSS Formatter, but presents a short validity result instead of rewriting the stylesheet. The editor is helpful for larger files because it shows line numbers and keeps input and output in separate scrolling panels.
Syntax validity is only one part of CSS quality. A rule can be well formed and still have no effect because of selector specificity, unsupported properties, or layout context. Test the rendered page in the browsers you support. This tool is useful before a review or when isolating a broken stylesheet; it processes source locally and does not upload it.
For long stylesheets, isolate the failing rule if the parser points near the end of a block. A missing closing brace earlier can make later declarations look invalid. The line and column are an investigation starting point, not a guarantee that the first typo is exactly there.
Frequently asked questions
Does this check whether a style looks right?
No. It checks parsing syntax, not rendered appearance.
Does it enforce a style guide?
No. It is a syntax check, not a CSS linter.
Can it find every unsupported browser feature?
No. Browser support and vendor behavior depend on the target environment.
Why is a property not flagged?
CSS can preserve unknown properties; a syntax check does not verify every property name or value.