Quick checks. Real answers.
Six free, read-only checks you can run on any website in seconds. Each one shows what is wrong, why it matters and how to fix it. For the complete picture, run the 40-point Safety Check.
SSL / TLS Checker
Check any website's SSL certificate, expiry, TLS 1.0/1.1, TLS 1.3, cipher strength, HSTS and mixed content. Free and instant.
Open the tool → Browser protectionSecurity Headers Checker
Check a website's security headers: Content-Security-Policy, HSTS, X-Frame-Options, nosniff, Referrer-Policy, Permissions-Policy, CORS and cookie flags.
Open the tool → Email securityDMARC, SPF & DKIM Checker
Check whether anyone can send email pretending to be your domain: SPF, DKIM, DMARC policy, MTA-STS and your mail servers' blacklist status.
Open the tool → ReputationIP & Domain Blacklist Checker
Check if your IP address, domain or mail servers are on Spamhaus, SpamCop, Barracuda, SORBS, SURBL, URIBL and other blacklists, plus Google Safe Browsing.
Open the tool → SoftwarePHP & Server Version Checker
Check which PHP, web server, CMS and JavaScript library versions a site announces, whether they are out of support, and which known vulnerabilities apply.
Open the tool → AI agentsAI Crawler & Bot Rules Checker
See whether your robots.txt sets rules for 20 AI crawlers such as GPTBot, ClaudeBot, PerplexityBot and Google-Extended, and whether anything enforces them.
Open the tool → Everything at onceFull Safety Check
All of these and more: 40 checks, a grade, and exactly which gaps SENTRA closes.
Run the Safety Check →See SENTRA on your own traffic.
Book a walkthrough, or start with a free Safety Check of your site.