Free Online Checkers - Validate URLs, SEO, Links, and Code
Run a quick check and get a clear pass or fail with the fix. These checkers are free and require no account.
37 tools in this section
Check Color Contrast for WCAG Accessibility Online
Test foreground and background color contrast against WCAG AA and AAA standards. Free online accessibility color contrast checker.
Test Regular Expressions Online
Test and debug regex patterns with real-time matching and group highlighting. Free online regex tester with explanation.
Compare Text & Find Differences Online
Compare two blocks of text and see additions, deletions, and changes highlighted. Free online diff checker.
Check Website SEO Online
Analyze your page for SEO issues including meta tags, headings, and content quality. Free online SEO checker.
Check & Explain Cron Expressions Online
Validate cron expressions and see when they'll run next. Free online cron expression checker with human-readable explanations.
Check Open Graph Tags & Preview Social Cards Online
Preview how your page appears when shared on Facebook, Twitter, and LinkedIn. Free online OG tag checker.
Check Text Similarity Online
Compare two texts and calculate the similarity percentage. Free online text similarity checker with diff highlighting.
Analyze Word Frequency Online
Count and rank the most frequently used words in any text. Free online word frequency analyzer.
Search Unicode Characters Online
Search and copy special Unicode characters, symbols, and emoji. Free online Unicode character finder.
Search HTML Entities Reference Online
Search and copy HTML entities with character previews. Free online HTML entity reference guide.
Check Browser Feature Support Online
Check CSS and HTML feature compatibility across browsers. Free online browser support checker.
DNS Lookup & Record Check Online
Query DNS records (A, MX, TXT, CNAME, NS, AAAA) for any domain. Free online DNS lookup tool.
Check SSL Certificate Details Online
Inspect SSL/TLS certificate details including issuer, expiration, and protocol. Free online SSL certificate checker.
Test Website Speed & Performance Online
Measure page load time, TTFB, and resource counts. Free online website speed test with optimization tips.
Find Broken Links on Web Pages Online
Extract and analyze all links from HTML source to find broken or problematic links. Free online broken link checker.
Check Redirect Chains Online
Trace and visualize HTTP redirect chains between URLs. Free online redirect chain checker.
Check HTTP Security Headers Online
Analyze HTTP response headers for security best practices. Free online security headers checker with scoring.
Check WCAG Color Contrast Ratio Online
Test text and background color contrast against WCAG 2.1 AA and AAA standards. Free online accessibility contrast checker.
Find Font Pairings Online
Discover beautiful font combinations for your designs. Free online font pairing tool with Google Fonts support.
Build & Test HTTP Requests Online
Build custom HTTP requests with headers, body, and authentication. Free online API request builder.
Look Up IP Address Information Online
Find geolocation, ISP, and network details for any IP address. Free online IP address lookup tool.
Count Words & Characters Online
Count words, characters, sentences, and paragraphs in any text. Free online word counter with reading time.
Check Grammar and Spelling Online
Check your text for grammar, spelling, and punctuation errors. Free online grammar checker powered by LanguageTool.
Check Readability Score Online - Flesch-Kincaid
Analyze the readability of your text with Flesch-Kincaid, Gunning Fog, and other scoring methods. Free online readability checker.
Check if a URL is Safe Online
Check any URL for malware, phishing, and safety issues. Free online URL safety checker.
Color Blindness Simulator Online - Test Accessibility
Simulate how your design looks to people with color blindness. Free online color vision deficiency simulator.
Check What My IP Address Is Online
See your public IP plus city, country, timezone, and ISP. Free IP lookup useful for VPN checks and network troubleshooting.
Check Button and Link Color Contrast Online
Test whether button text and link colors meet WCAG contrast rules. Free online color contrast checker for UI components.
Check MX Records for a Domain
Check the MX records for any domain and verify email delivery configuration. Free MX record lookup with mail server priorities, no signup.
Check SPF and DKIM TXT Records
Look up SPF and DKIM TXT records for any domain to verify email authentication. Free TXT record checker with full record values, no signup.
Check SSL Certificate Expiry Date
Check when an SSL certificate expires and see the days remaining for any domain. Free SSL expiry checker with issuer and validity details.
Check a Web Page for Broken Links and 404s
Scan a web page for broken links and 404 errors across internal and external links. Free broken link checker for SEO, no signup.
Check a URL Redirect Chain and 301 Hops
Trace the full redirect chain for any URL and check 301, 302, 307, and 308 hops. Free redirect checker that detects loops and extra hops.
Check Security Headers - CSP, HSTS and More
Audit a site's HTTP security headers including CSP, HSTS, and X-Frame-Options. Free security headers checker with a header score, no signup.
Is This Link Safe? Check a URL Before Clicking
Check if a link is safe before clicking it. Scan a URL for malware, phishing, bad certificates, and suspicious redirects online for free, no signup.
Scan a URL for Malware and Phishing
Scan any URL for malware, phishing, and scam patterns online for free. Inspect certificates, redirects, and security headers before you open the link.
Proofread an Essay Online Free
Proofread an essay online for free with grammar, spelling, and style checks. No signup, no extension, and no word limit. Apply fixes with one click.
Full Tool Pages
About These Tools
Every tool in this section is free and runs entirely in your browser on ToolBox. There are no uploads, no accounts, and no usage limits, so your files and data stay on your own device. Browse the full tool directory for everything else.