The Complete Guide to Free Checker and Validator Tools
TL;DR: Checker and validator tools test whether something is correct, secure, working, or optimized. From SSL certificates to password strength, broken links to...
SSL, Passwords, Links, Email, JSON, Readability, and More
TL;DR: Checker and validator tools test whether something is correct, secure, working, or optimized. From SSL certificates to password strength, broken links to JSON syntax, email deliverability to color accessibility, free validators catch problems before they reach users, clients, or search engines. This guide maps every checker tool by what it validates.
I keep a bookmark folder called "Check Everything." Before I send, publish, launch, or share anything, I run it through the relevant checker. This habit catches problems that would otherwise reach clients, damage rankings, or create security vulnerabilities.
Here's every checker and validator available, organized by what it tests.
Security Checkers
- SSL Checker: Validate HTTPS certificates
- Password Strength Test: Evaluate password security
- Password Leak Checker: Check passwords against breach databases
- Credit Card Validator: Verify card number formatting
Guide: Password security, Privacy audit.
Website and Network Checkers
- Website Status Checker: Confirm site availability
- HTTP Status Code Checker: Verify response codes
- Broken Link Checker: Find dead links
- Redirect Checker: Trace redirect chains
- GZIP Compression Test: Verify server compression
- Open Port Checker: Test port accessibility
Guides: Network tools, Website debugging.
Email Checkers
- Email Validator: Verify email address format and deliverability
- Online SMTP Test: Test email server connectivity
Guide: Email deliverability.
Data Validators
- JSON Validator: Check JSON syntax
- Palindrome Checker: Verify string properties
Guide: JSON tools.
Content Checkers
- Grammar Checker: Spelling, grammar, and style
- Readability Scorer: Reading level analysis
- Text Similarity Checker: Content originality comparison
- Language Detector: Identify text language
Guide: Writing tools.
Design Checkers
- Color Accessibility Checker: WCAG contrast compliance
Guide: Accessibility guide.
SEO Checkers
- Meta Tag Preview: Search result appearance
- Open Graph Preview: Social sharing display
- Keyword Density Analyzer: Keyword frequency analysis
- Word Density Counter: Word frequency analysis
Guide: SEO audit.
Domain and URL Checkers
- Domain WHOIS: Registration details
- DNS Lookup: DNS record verification
- MX Lookup: Mail server records
- URL Unshortener: Reveal shortened URL destinations
Guides: URL tools, Network tools.
Quick Reference: Which Checker Do I Need?
| I need to verify... | Checker |
|---|---|
| Website is online | Website Status Checker |
| SSL certificate valid | SSL Checker |
| No broken links | Broken Link Checker |
| Server compresses responses | GZIP Test |
| Email address works | Email Validator |
| Email server delivers | SMTP Test |
| Password is secure | Password Strength Test |
| Password not breached | Password Leak Checker |
| JSON syntax correct | JSON Validator |
| Writing is error-free | Grammar Checker |
| Text is readable | Readability Scorer |
| Colors are accessible | Color Accessibility Checker |
| Search listing looks right | Meta Tag Preview |
| Social share looks right | Open Graph Preview |
| Domain is registered | Domain WHOIS |
| DNS records correct | DNS Lookup |
| Redirect works properly | Redirect Checker |
The Pre-Publish Validation Chain
Before publishing or sharing anything:
- Grammar Checker → writing quality
- Readability Scorer → audience fit
- Meta Tag Preview → search appearance
- Open Graph Preview → social appearance
- Broken Link Checker → link health
- Color Accessibility → design compliance
Six checks. Five minutes. Catches 95% of common problems.
Advanced workflows: Automation guide, Power user guide.
FAQ
How often should I run checkers on my website? SSL and status: monthly. Broken links: monthly. GZIP: after server changes. Meta tags and OG: after content updates. Passwords: monthly.
Which checker is most important? SSL Checker for security, Broken Link Checker for user experience, and Grammar Checker for credibility. All three prevent the most common professional embarrassments.
Can I automate these checks? Browser-based checks are manual. For automated monitoring, paid uptime services complement manual validation. The pre-publish chain is fast enough to run manually each time.
Do checkers fix problems or just find them? They find problems. The corresponding generator or processing tools fix them. Checkers diagnose; other tools treat.