Alternatives

Products that do what Perimeter does

Check your site's TLS, headers, DNS and accessibility

1. 1
   bypassed.me▲2

   📎169 free DNS, email, TLS diagnostics in one place + more!

   Jul 2026 · bypassed.me

2. 2FC
   Free Certificate Monitoring via RSS▲120

   2024 · raphting.dev

3. 3NH
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   2022 · haveibeenexpired.com

4. 4
   KIT.domains▲28

   Domain infrastructure monitoring across all registrars

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5. 5
   CertPost▲3

   SL monitoring that checks the certificate your server serves

   Aug 2026 · certpost.ai

6. 6
   Certly▲7

   Know before your SSL, domain, or DNS breaks

   Jul 2026 · certly.dev

7. 7OT
   Osint tool that finds exposed files on domains▲58

   hey guys, wanted to show one of my side projects i just made public. the idea is basically another osint tool for pentesters and bug bounty hunters. it watches certificate transparency logs and checks newly-seen domains for exposed stuff like .env files, open .git dirs, config files, db dumps and so on, and puts whatever it finds into a searchable db. you just search a domain (or part of one) and see what's exposed. it's read-only and free. one thing i've been thinking about adding is a way to register for certain keywords and get notified when something new shows up for that search. would…

   Jul 2026 · search.cerast-intelligence.com

8. 8TC
   TLS cert expiration dashboard▲40

   2016 · github.com

9. 9
   SiteLock▲3

   Free website security scanner that grades any site A to F

   May 2026

10. 10
    SSL Certificate Checker▲11

    Check SSL certificates across public endpoints

    Jul 2026 · apify.com

11. 11
    CheckCyber▲4

    Scan any website for 24 security flaws in seconds

    Jul 2026 · checkcyber.fr

12. 12
    CertFleet▲1

    SSL + uptime monitoring without the observability bill

    23d ago

13. 13
    Domain Scan Tools▲5

    Detect domain security issues before they hurt your business

    May 2026 · domainscan.tools

14. 14
    Email Posture▲5

    Get alerted the moment your DMARC, SPF, or DKIM breaks

    Jul 2026 · emailposture.com

15. 15
    Cyboruz▲2

    Scan your website for security SSL & email issues in seconds

    Apr 2026 · cyboruz.com

16. 16
    GuardScan, Free Website Security Scanner▲2

    Scan any website for security issues in 10 seconds. Free.

    Feb 2026

17. 17
    Domain Watchdog▲3

    Catch every client domain problem before it costs you

    Jul 2026 · domainwatchdog.app

18. 18
    CertChecker▲1

    Never find out an SSL cert expires too late

    22d ago · certchecker.dev

19. 19
    trustyourinbox▲8

    DMARC Monitoring For Everyone Who Isn't A Security Team

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20. 20
    Auditly — Scan before you ship▲3

    Free security scan that tells you exactly how to fix it

    Jun 2026

21. 21
    Email Deliverability Toolkit▲9

    9 free tools to keep your email out of spam

    9d ago · truelist.io

22. 22CF
    CertRadar – Find every certificate ever issued for your domain▲21

    Jan 2026 · certradar.net

23. 23
    WebSentry▲1

    Instant A–F security grades for any website with monitoring

    May 2026 · websentry.dev

24. 24WF
    Watch/filter new domains from certificate transparency logs▲7

    This can be used to find phishing domains or domains matching any pattern you want if you select "custom filter." You can also connect over WebSocket at /ws and use any programming language you want. There may be duplicates because some domains are published in multiple logs. I get data from all of the logs currently included with Chrome, a list of which is available here: https://github.com/google/certificate-transparency-community....

    2024 · firehose.lol

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