Validation & Testing Tools Page
Validate data formats, test regular expressions, and verify various input types.
BIMI Record Checker & Logo Validator
Verify BIMI (Brand Indicators for Message Identification) DNS records for any domain and validate the SVG logo file against the strict SVG Tiny Portable/Secure (SVG Tiny PS) profile required for email client display. Checks DNS record syntax at default._bimi.{domain}, fetches the logo URL, validates SVG profile compliance (no scripts, no animations, square aspect ratio, file size), and checks the Verified Mark Certificate (VMC) or Common Mark Certificate (CMC) required by Gmail and Apple Mail.
Broken Link Checker
Find broken links, 404 errors, and redirects on your website. Check single pages or crawl sites (up to 100 pages, crawl depth 10, 500 links checked) with detailed reports.
Canonical URL Checker
Check if a website has proper canonical URL tags and identify potential SEO issues
Contrast Checker
Check the contrast ratio between two colors to ensure accessibility (WCAG AA/AAA) compliance.
CORS Header Checker
Check CORS (Cross-Origin Resource Sharing) headers configuration for any website or API endpoint
Credit Card Validator & Test Number Generator
Validate credit card numbers with the Luhn algorithm, check a whole batch at once, and generate synthetic Luhn-valid test cards for 14 brands — all in your browser, with no data sent anywhere.
CSS Validator
Validate CSS stylesheets for syntax errors, deprecated properties, and performance issues. Get vendor-prefix suggestions and best-practice warnings. Perfect for front-end developers and designers.
DKIM Record Checker
Look up and validate DKIM (DomainKeys Identified Mail) records for any domain and selector. Auto-discovers common selectors used by Google Workspace, Microsoft 365, SendGrid, Mailgun and others. Validates public key length (1024 vs 2048-bit), signing algorithm (RSA-SHA256), and record syntax for email authentication compliance.
DMARC Generator & Checker
Build a valid DMARC (Domain-based Message Authentication, Reporting & Conformance) DNS record interactively, or check an existing DMARC policy for any domain. The generator walks you through every tag — policy (p=), pct, aggregate reports (rua), forensic reports (ruf), alignment modes (adkim, aspf), and reporting interval — with inline explanations. The checker parses any published DMARC record and flags syntax issues, missing required tags, and report-address (rua/ruf) problems such as a missing mailto: prefix. If the domain has no record, it uses the organizational domain's record, as receivers do.
DNS Lookup Tool
Resolve domain names to IP addresses and fetch DNS records (A, AAAA, MX, TXT, CNAME, etc.). Perfect for network diagnostics, domain analysis, and troubleshooting DNS issues.
Email Header Analyzer & Tracer
Paste full email headers and see the message's delivery path, SPF/DKIM/DMARC verdicts as recorded by the receiving server, a risk score, and per-hop server details. Surfaces phishing red flags including authentication failures, brand-impersonating display names (e.g. "PayPal Support" sent from an unrelated domain), and elevated risk scores — useful even when SPF/DKIM/DMARC technically pass.
Email Validator
Quickly check if an email address is valid. Validates email format and syntax in your browser and gives detailed feedback on common issues, including likely domain typos.
HTML Validator
Check HTML against the official W3C Nu validator and see every error in context: line and column, the exact offending markup with the failing range highlighted, and a jump-to-line source view. Paste, upload, or load a URL.
HTTP Header Checker
Inspect the HTTP response headers of a given URL to debug caching, security, and SEO issues. Analyze response headers for performance optimization and security best practices.
IP Address Lookup
Look up information about IP addresses including geolocation, organization, hostname, and network details. Supports both IPv4 and IPv6 addresses.
IP Blacklist Check
Check if an IP address is listed on about 50 DNS-based blacklist (DNSBL) services. Verify email server reputation and check spam, proxy, and malware databases for IPv4 addresses.
JSON Validator
Validate JSON input for proper structure and syntax. Format, minify, and analyze JSON data. Perfect for debugging API payloads or configuration files.
JWT Decoder
Paste a JWT (JSON Web Token) and decode its header and payload. Useful for developers to inspect JWT contents without verification.
JWT Encoder
Create and encode JSON Web Tokens (JWT) with custom header, payload, and secret key. Perfect for developers testing JWT implementation.
MX Lookup Tool
Look up MX (Mail Exchange) records for any domain. See mail server hostnames sorted by priority, resolved IP addresses, whether each hostname resolves, and detected email provider — for diagnosing email delivery and verifying inbound mail routing.
NS Lookup Tool
Query nameserver (NS) records for any domain. Discover authoritative DNS servers, verify DNS delegation, and troubleshoot DNS configuration issues with detailed NS record lookups.
Password Strength Checker
Analyze password strength in real-time based on length, guessable patterns, an entropy estimate, and common vulnerabilities. Get detailed feedback to improve password security.
Regex Tester
Test regular expressions with sample text. Find matches, test patterns, and debug regex with real-time match highlighting and capture-group details.
Robots.txt Tester
Test and validate robots.txt files for crawling permissions. Check if specific URLs are allowed or disallowed for search engine bots and web crawlers. Essential for SEO optimization.
SMTP Test Tool
Test any SMTP server's connection, authentication, TLS/SSL setting, and delivery. Diagnose connection refused, authentication failures, TLS errors, and relay errors before they reach production — without firing up Telnet or a test mail client.
SPF Checker & Validator
Validate and analyze SPF (Sender Policy Framework) records for any domain. Check SPF syntax, detect configuration issues, count DNS lookups through nested includes, identify deprecated mechanisms, and ensure email authentication compliance with comprehensive validation reports.
SSL Certificate Checker
Check SSL certificate details, expiration dates, and security status for any domain. Verify chain trust, hostname match, issuer information, and the negotiated TLS version.
User Input Sanitizer Tester
Test user input strings against XSS, SQL injection, and other vulnerabilities. Compare sanitization methods on your input. Essential for web application security testing.
User-Agent Parser
Parse and analyze User-Agent strings to extract detailed information about browsers, operating systems, devices, and engines. Perfect for web analytics and debugging.
XSS Payload Tester
Browse 65 documented XSS vectors — event handlers, SVG, DOM clobbering, mXSS, CSTI, polyglots and filter-evasion encodings — then run any of them in four sandboxed iframes to see exactly which injection contexts execute, which are blocked by CSP, and which just throw.
YAML Validator
Validate YAML syntax with line/column error pinpointing. Catches indentation errors, tabs in indentation, duplicate keys, and invalid escape sequences. Shows the parsed structure for inspection.