CSS Validator
Validate CSS syntax instantly in your browser. Get real-time feedback on errors and warnings with exact line and column numbers. Shows rule count, declarations, selectors, at-rules, and comment statistics.
How to Use CSS Validator
How to Use the CSS Validator:
Paste Your CSS: Type or paste your CSS into the input area. Validation happens in real-time as you type — no button press needed.
Read the Status Banner: A green "Valid CSS" banner means your CSS is syntactically correct. A red "Invalid CSS" banner shows the number of errors found.
Fix Issues: The Issues panel lists every error and warning sorted by line number. Each item shows the line, column, and a description of the problem.
Review Statistics: The Statistics panel shows line count, rule count, declarations, selectors, at-rules, and comment count for your stylesheet.
Use Examples: Click the example buttons (Button styles, Flexbox layout, Variables + @media, Animation, Invalid) to load sample CSS and see how the validator works.
Clear: Click the Clear button to reset the editor and start fresh.
Errors detected:
- Unclosed comment — a /* comment was opened but never closed with */
- Missing selector before { — an opening brace appears with no selector before it
- Unexpected } — a closing brace appears without a matching opening brace
- Unclosed { — an opening brace was never closed
Warnings detected:
- Missing colon — a declaration inside a rule block has no colon (e.g.
color redinstead ofcolor: red) - Duplicate property — the same CSS property appears more than once in the same rule block
Common CSS Mistakes:
- Forgetting to close a rule block with }
- Writing
color redinstead ofcolor: red - Leaving a /* comment open without closing it
- Accidentally duplicating a property like
marginin the same rule
Frequently Asked Questions
Most Viewed Tools
Screen Size Converter
Calculate screen width and height from diagonal size and aspect ratio. Convert between inches and centimeters for displays, TVs, and monitors with instant dimension calculations.
Use Tool →DPI Calculator
Calculate DPI (dots per inch), image dimensions, and print sizes. Convert between pixels and physical dimensions for printing and displays.
Use Tool →Paper Size Converter
Convert between international paper sizes (A4, Letter, Legal) with dimensions in mm, cm, and inches. Compare ISO A/B series and North American paper standards.
Use Tool →Fuel Consumption Converter
Convert between MPG (miles per gallon), L/100km (liters per 100 kilometers), and other fuel efficiency units. Compare car fuel economy across different measurement systems.
Use Tool →CSV Splitter
Split large CSV files into smaller files by number of rows. Process large datasets in manageable chunks instantly.
Use Tool →Product Schema Generator
Generate JSON-LD Product schema markup for SEO. Add product details like name, price, brand, rating, and availability to create structured data for rich search results.
Use Tool →Large Text File Viewer
View and search large text files up to 200MB in your browser. Features virtual scrolling, line numbers, search functionality, and file statistics. Perfect for log files, CSV, JSON, and code files.
Use Tool →API Key Generator
Generate secure, cryptographically random API keys for authentication and authorization. Create custom API keys with various formats including hex, base64, and prefixed keys.
Use Tool →Related Development Tools
JSON Formatter & Validator
FeaturedFormat, validate, and pretty-print JSON with our developer-friendly editor.
Use Tool →QR Code Generator
FeaturedCreate custom QR codes for URLs, text, and contact info
Use Tool →HTML Validator
Validate HTML markup and check for common issues. Detect missing attributes, accessibility problems, deprecated tags, and structure errors. Free and runs entirely in your browser.
Use Tool →CSV Null Value Handler
Handle null and empty values in CSV - Replace, remove, or keep missing data with flexible null handling strategies
Use Tool →CSV Data Type Converter
Convert data types in CSV - Transform CSV column values to numbers, booleans, dates with automatic type detection and cleaning
Use Tool →CSV to Excel Converter
Convert CSV to Excel - Transform comma-separated values to Excel spreadsheet with auto-width columns
Use Tool →TSV to CSV Converter
Convert TSV to CSV - Transform tab-separated values to comma-separated values with automatic quoting
Use Tool →Slug Generator
Generate URL-friendly slugs from any text. Create SEO-optimized slugs for blog posts, products, and web pages instantly.
Use Tool →Share Your Feedback
Help us improve this tool by sharing your experience