CSS Validator

What does this CSS validator check?

Paste CSS and get a line-by-line report of structural and syntax problems — the class of mistake that breaks parsing, not the class that produces the wrong color. Specifically, it checks for:

• Unbalanced braces ({ / }) — a rule block opened but never closed, or a stray closing brace with no matching opener.
• Unbalanced parentheses inside values, such as a calc(100% - 10px missing its closing ).
• Unterminated string literals — an opening ' or " with no matching close before the line ends or the file ends. CSS strings can't span multiple lines unless the line break is backslash-escaped.
• Unterminated /* comment */ blocks — a comment opener with no closing */.
• Empty rule blocks (selector {}) — flagged as a warning, since they're technically valid CSS but almost always leftover or dead code.
• A property with no value (color: ;) or a value with no property (: red;).

Each finding lists the line number, whether it's an error or a warning, and a plain-language message. If none of the above are found, you get a single "Valid CSS — no structural issues found" result.

What it does NOT check

This is a lightweight structural scanner, not a full CSS parser. It does not validate CSS's actual value grammar — it won't catch color: notacolor;, an invalid unit, a misspelled property name, or an unsupported value for a given property, because that requires knowing the complete, ever-growing CSS3 specification for every property. For that level of validation, use your browser's DevTools (the Styles panel greys out and flags properties/values it doesn't recognize) or a dedicated linter like Stylelint.

Who is it for?

• Developers hunting down a missing } or ) that's silently breaking the rest of a stylesheet.
• Anyone pasting CSS from an unfamiliar source (a snippet, an AI generation, a copy-paste from docs) who wants a quick sanity check before using it.
• Code reviewers scanning for empty, likely-accidental rule blocks.

How to use it

1. Paste your CSS into the input box — results update live as you type.
2. Read the Line/Type/Message table: errors are structural breaks worth fixing immediately; warnings (like empty rule blocks) are worth a look but won't break rendering.
3. Copy or download the results as CSV if you need to share them.

FAQ

Will it catch a typo like bakground-color? No — unknown property names are a semantic check, not a structural one. The browser will simply ignore a property it doesn't recognize; this tool only tells you when the CSS itself can't be parsed correctly.

Why does it flag an empty rule block as a warning instead of an error? selector {} is valid CSS — browsers parse it fine — but it does nothing, so it's almost always a mistake (a forgotten declaration, or dead code left behind after edits).

Does it support nested CSS or @media blocks? Yes — brace/paren/string/comment tracking works at any nesting depth, so @media, @supports, and nested selector blocks are all checked the same way.

Privacy

Validation happens entirely in your browser. Your CSS is never uploaded or sent anywhere.