Syntax & Logic Checkers

Validate Code & Data Instantly

Don't let a missing comma break your build. Validate JSON, check XML structure, and lint Code files directly in your browser.

Secure Validation (No Uploads)

Exact Error Line Detection

Standard Compliance

Validation Tools

20 Linters Available

Alt Tag Checker

Check HTML images for missing alt attributes to improve accessibility and SEO compliance. Essential for WCAG compliance and screen reader support.

Broken Link Checker

Check webpages for broken or unreachable links with detailed error reporting. Essential for website maintenance, SEO preservation, and user experience.

Color Contrast Checker

Calculate the exact contrast ratio between two colors and instantly check WCAG 2.1 AA and AAA compliance for normal text, large text, and UI components.

Data Quality Checker

Analyze CSV and JSON data quality with comprehensive statistics, duplicate detection, and data profiling for data cleaning workflows.

Data Validation Rule Builder

Build comprehensive data validation queries for migration testing. Generate checksums, row counts, and integrity checks between source and target databases.

IP Address Intelligence Dashboard

Discover comprehensive information about your IP address, geolocation, ISP details, and VPN detection for network troubleshooting and security.

JSON Formatter & Validator Pro

Format and validate JSON code with syntax highlighting, error detection, and beautification. Essential for API development and data structure validation.

Keyword Density Checker

Analyze keyword frequency and density in text content for SEO optimization. Calculate percentages, identify frequent words, and maintain natural keyword distribution.

PageSpeed Insights Checker

Analyze website performance using Google PageSpeed Insights API with Core Web Vitals, optimization recommendations, and mobile/desktop comparison.

Password Breach Checker

Check if your password appeared in known data breaches using secure Have I Been Pwned database. Protect against credential stuffing with privacy-focused partial hash checking.

Password Strength Checker

Test password security with real-time vulnerability analysis and improvement suggestions. Privacy-focused tool with local processing and actionable recommendations.

PDF Permission Checker

Check what permissions a PDF allows: printing, copying, editing, annotations, and more. Instant client-side analysis with no file uploads.

PHP Version Compatibility Checker

Analyze PHP code compatibility across versions 7.0-8.3. Detect deprecated functions, breaking changes, and get migration recommendations instantly.

Plagiarism Checker

Check text for plagiarism using API integration with detailed scoring and source matching for content originality verification.

Python Data Validation Schema Generator

Generate Pydantic models and dataclasses from JSON/CSV data automatically. Create type-safe Python schemas with validation rules, optional fields, and nested structures for data engineering.

Screen Reader Compatibility Checker

Test your website's accessibility for screen readers. Free online tool to check ARIA labels, semantic HTML, keyboard navigation, and screen reader compatibility.

SHACL Validator

Validate RDF data against SHACL shapes online. Free SHACL validator with Turtle, JSON-LD, and RDF/XML support for semantic web development.

Sitemap Validator

Validate XML sitemap files with structure checking, URL validity verification, and compliance guidance for proper search engine indexing.

SQL Beautifier & Validator

Format messy SQL code into clean, readable queries with consistent indentation. Support for multiple SQL dialects and professional database development.

Title and Meta Length Checker

Check meta titles and descriptions for search engine character limits with real-time validation and mobile/desktop preview modes.

Why Validate Online?

Ensure your data integrity and code quality before deployment.

Data Integrity

Working with JSON APIs or XML feeds? One syntax error can crash your application. Our validators parse your data structure to find missing brackets, unclosed tags, or invalid types instantly.

Configuration Safety

DevOps engineers use our tools to check YAML, TOML, or ENV files. Because we run locally (client-side), you can safely paste configs containing sensitive API keys without fear of leaks.

Web Standards

Ensure your markup meets W3C standards. Validating HTML and CSS helps prevent browser rendering issues and improves your website's SEO performance by ensuring clean code.

Validation FAQ

What is the difference between Validating and Formatting?

Formatting (Beautifying) makes code readable. Validating (Linting) checks if the code is actually correct and follows the rules of the language.

Is it safe to validate files with passwords/keys?

On Selqio, yes. Because we use Client-Side processing, your data never leaves your computer. We recommend this over server-based validators for sensitive data.

Do you fix the errors automatically?

Our tools will highlight the exact line and reason for the error. Some tools (like JSON Validator) have a "Fix" button for common syntax mistakes.

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