diff --git a/README.md b/README.md
index 33b4899c..efafc25f 100644
--- a/README.md
+++ b/README.md
@@ -607,6 +607,7 @@ This list results from Pull Requests, reviews, ideas, and work done by 1600+ peo
   * [letsencrypt.org](https://letsencrypt.org/) - Free SSL Certificate Authority with certs trusted by all major browsers
   * [meterian.io](https://www.meterian.io/) - Monitor Java, Javascript, .NET, Scala, Ruby, and NodeJS projects for security vulnerabilities in dependencies. Free for one private project, unlimited projects for open source.
   * [Mozilla Observatory](https://observatory.mozilla.org/) - Find and fix security vulnerabilities in your site.
+  * [Otterwatch](https://otterwatch.dev/) - Daily SSL/TLS certificate monitoring: expiry alerts (30/7/1 day), chain and OCSP revocation checks, and certificate transparency issuance history. Free forever for 5 domains, no credit card.
   * [Protectumus](https://protectumus.com) - Free website security check, site antivirus, and server firewall (WAF) for PHP. Email notifications for registered users in the free tier.
   * [Public Cloud Threat Intelligence](https://cloudintel.himanshuanand.com/) - High confidence Indicator of Compromise(IOC) targeting public cloud infrastructure, A portion is available on github (https://github.com/unknownhad/AWSAttacks). Full list is available via API
   * [pyup.io](https://pyup.io) - Monitor Python dependencies for security vulnerabilities and update them automatically. Free for one private project, unlimited projects for open source.