Syntax Checker & Code Validator
About CSS Syntax Checker
The CSS Syntax & Stylesheet Validator scans raw CSS, SCSS, and CSS Modules for unclosed curly braces, missing semicolons, malformed selector syntax, invalid `@rules`, and broken CSS custom properties (`var(--name)`).
How to Use CSS Syntax Checker
Step 1
Paste CSS or SCSS code into the input pane.
Step 2
Review the live syntax validation indicator.
Step 3
Inspect highlighted line numbers for syntax anomalies or unclosed blocks.
Step 4
Click "Copy Report".
Practical Use Cases for CSS Syntax Checker
Catching Silent CSS Syntax Errors Before Production
Find missing closing braces (`}`) and malformed media queries that cause browsers to silently discard entire CSS stylesheets.
Validating CSS Variable & `@keyframes` Syntax
Check syntax correctness for complex CSS animations, grid templates, and CSS custom property fallback declarations.
Input & Output Examples
Detecting Unclosed Curly Brace in CSS Rule
`.card { display: flex; color: #fff; .button { padding: 10px; }`Status: ❌ CSS Syntax Error | Message: `Unclosed block at line 1, column 1; missing matching '}'`
Key Features & Performance
- ✓Audits modern CSS: CSS Grid, Flexbox, Nesting (CSS Native Nesting), `@container` queries, `@layer`, and CSS variables.
- ✓Pinpoints exact Line and Column coordinates for invalid selector and declaration syntax.
- ✓100% Client-Side memory execution via PostCSS AST parser.
- ✓1-Click Copy CSS error diagnostic report.
Key Terminology & Definitions
CSS Declaration Block
The set of CSS property-value pairs enclosed within curly braces (`{ ... }`) attached to a selector.
Native CSS Nesting
The CSS standard allowing style rules to be nested directly inside parent selectors without requiring SASS or Less preprocessors.