CSS Validator

Scan your CSS for syntax errors and missing braces

Error Shield

Catch structural mistakes before they break your styles

A single missing brace can make the browser ignore every rule after it, and it is often hard to spot in a long stylesheet. This validator scans your CSS line by line, looks for the most common structural mistakes and reports each one with its line number, so you can jump straight to the problem.

Running a scan

Paste your code into the CSS to Validate box. Clear removes the text and any earlier report, and Sample Error inserts a short snippet that contains a deliberate problem so you can see how results look.
Click Start Deep Scan.
If nothing is found, a green panel confirms that no errors were detected. Otherwise a red Syntax Errors Detected panel lists each issue with a LINE badge and a message.
A footer reports Total Rules Analyzed, counted from the number of opening braces.

What it looks for

Unexpected closing brace: a closing curly bracket with no matching opening one before it.
Unclosed opening brace: a block that is opened but never closed. The report points at the line where the block began.
Possible missing semicolon: a line that looks like a property and value pair, with no semicolon and no brace on the same line.

When to reach for it

Finding why a page suddenly lost its styling after an edit.
Checking a stylesheet after resolving a merge conflict.
Reviewing CSS copied from a forum or tutorial before adding it to a project.
Teaching beginners how missing braces and semicolons affect a stylesheet.

Read the results with care

This is a lightweight structural check, not a full validator such as the W3C service. It does not know which property names or values are legal, so a typo like colour instead of color, or an invalid value, will pass. The green message therefore means that the braces balance and no obvious semicolon problem was seen, not that every rule is guaranteed to work.

The semicolon warning is a guess. CSS allows the last declaration in a block to omit its semicolon, and multi-line values may also trigger it, so treat that message as something to look at, not always as an error. Braces inside comments or strings are still counted, which can produce false alarms. Once you have fixed the reported lines, run the scan again, since one repaired brace can clear several messages at once. The scan takes place in your browser using JavaScript.

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Frequently Asked Questions

Does this replace the official W3C CSS validator?

No. It checks brace balance and likely missing semicolons only. It does not verify property names, values or browser support, so a misspelled property will not be reported here, unlike in a full validator.

Why was a semicolon flagged when my CSS is fine?

The last declaration in a block may legally omit its semicolon, and some multi-line values look incomplete line by line. The message says possible for that reason, so confirm each case yourself.

What does Total Rules Analyzed mean?

It is the number of opening curly braces found in your input. That includes at-rules and nested blocks, so it may be higher than the number of plain selectors in your stylesheet.

How are unclosed blocks reported?

Any opening brace that never receives a closing one is listed as an unclosed brace, with the line number where it was opened. Add the missing brace after the block and scan again.

Will braces in comments cause problems?

They can. The scanner does not skip comments or quoted strings, so a brace inside one is counted like any other. If you get an unexpected report, check for braces in those places.