Online Validators
Validate data formats and check security instantly. Verify JSON syntax, HTML structure, email addresses, URLs, and password strength. Essential tools for developers, testers, and anyone working with data validation. All processing happens in your browser for complete privacy.
JSON Validator
Validate JSON syntax and find errors with detailed line numbers. Format and prettify JSON data.
HTML Validator
Check HTML for syntax errors, unclosed tags, and structural issues. Improve code quality.
Email Validator
Validate email address format. Check for common typos and invalid patterns.
URL Validator
Validate URL format and structure. Check protocols, domains, and path syntax.
Password Strength Checker
Analyze password security. Get recommendations for creating stronger passwords.
Why Use Online Validators?
Validation is the process of checking whether data conforms to expected formats and rules. Invalid data causes application crashes, security vulnerabilities, and poor user experiences. Catching errors early — before they reach production — saves time, money, and headaches.
Online validators provide instant feedback without installing development environments or running build processes. Paste your JSON, HTML, email, or URL and get immediate results. Our tools process everything locally in your browser, so sensitive data never leaves your device.
Types of Validation We Offer
- Syntax Validation: Check if JSON, HTML, or other formats follow structural rules
- Format Validation: Verify email addresses and URLs match expected patterns
- Security Validation: Analyze password strength and identify vulnerabilities
- Semantic Validation: Check if HTML uses proper nesting and tag structures
Benefits of Client-Side Validation
Unlike server-based validators that upload your data, our tools run entirely in your browser:
- Privacy: Your code and data never leave your device
- Speed: No upload/download delay — validation happens instantly
- Security: Passwords and sensitive data stay on your computer
- Offline: Works without internet after initial page load
Common Use Cases
Development & Debugging
Developers constantly debug JSON APIs, validate configuration files, and check HTML output. A single missing comma in JSON breaks entire applications. Validators pinpoint the exact line and character where errors occur, saving hours of debugging.
- • Debug API responses with syntax errors
- • Validate configuration files before deployment
- • Check HTML email templates
- • Verify webhook payloads
Quality Assurance
QA teams validate form inputs, test email collection, and verify URL generation. Validators help create test cases for edge cases — malformed emails, URLs with special characters, or intentionally broken JSON.
- • Test form validation logic
- • Verify email format requirements
- • Create edge case test data
- • Validate API response formats
Security & Compliance
Security teams enforce password policies, validate input sanitization, and check URL safety. Password strength checkers help users create secure credentials. URL validators identify potentially malicious links.
- • Enforce password complexity requirements
- • Check password against common patterns
- • Validate user-submitted URLs
- • Verify email format before account creation
Data Processing
Data analysts validate JSON exports from databases, check data feeds, and verify configuration imports. Catching format errors before processing prevents corrupted datasets and failed pipeline jobs.
- • Validate data exports before import
- • Check JSON/CSV conversion accuracy
- • Verify API data format compliance
- • Debug ETL pipeline inputs
Understanding Validation
JSON Validation
JSON (JavaScript Object Notation) has strict syntax rules. Keys must be quoted strings, values must be valid types, and commas must separate elements properly. A single typo — a missing comma, an extra bracket, or an unquoted key — makes the entire JSON invalid.
Our validator identifies the exact position of syntax errors, explains what's wrong, and can auto-format valid JSON for readability.
Try JSON Validator →Email Validation
Valid email addresses follow the pattern: local-part@domain. The local part can contain letters, numbers, and certain special characters. The domain must be a valid hostname with a proper top-level domain (TLD).
Our validator checks RFC 5322 compliance, detects common typos (like .con instead of .com), and identifies obviously fake patterns.
Try Email Validator →Password Strength Analysis
Password strength depends on length, character variety, and unpredictability. Our checker analyzes passwords against common patterns, dictionary words, keyboard sequences, and repeated characters. We estimate how long it would take to crack.
Important: Your password never leaves your browser. All analysis happens locally, so you can safely check real passwords without risk.
Try Password Strength Checker →Frequently Asked Questions
Is it safe to check my password here?
Yes. The password strength checker runs entirely in your browser. Your password is never sent to any server, never logged, and never stored. When you close the page, the password is gone from memory. This is safer than most online password checkers.
What makes JSON invalid?
Common JSON errors include: unquoted keys, trailing commas after the last element, single quotes instead of double quotes, unescaped special characters in strings, and using JavaScript values like undefined or NaN.
Does the email validator check if the email exists?
No. Our validator checks format compliance — whether the email address follows proper syntax rules. To verify if an email actually exists and can receive mail, you would need a service that attempts delivery or queries mail servers (which we don't do for privacy reasons).
How accurate is the password crack time estimate?
Crack time estimates assume offline brute-force attacks with modern hardware. Actual security depends on many factors: whether the password was in a data breach, the hashing algorithm used, and online rate limiting. Our estimates are conservative — real attacks may be slower due to these protections.
Can I validate URLs with query parameters?
Yes. Our URL validator handles full URLs including protocols (http, https, ftp), domains, paths, query strings, and fragments. It validates each component according to RFC 3986 standards.
Start Validating
Choose a validator and check your data instantly. Free, fast, and completely private.