Top cybersecurity Substacks provide in-depth analysis, industry trends, and technical insights from expert practitioners. Top, highly recommended, and frequently cited newsletters include Venture in Security (Ross Haleliuk), tl;dr sec (Clint Gibler), Aphinia (Misha Sobolev), Resilient Cyber, and The Cloud Security Guy, covering topics from CISO insights to AI and app security.

Why These Substack Newsletters?

• Actionable Advice: Many, like Resilient Cyber and Securely Built, offer practical tips for implementing security.
• In-depth Analysis: Unlike daily news alerts, these provide detailed, expert viewpoints on why a development matters.
• Focused Niches: Readers can choose specialized content, such as cloud (Cloud Security Guy) or, market analysis (Venture in Security). 

Source: Google AI Overview. 2/16/26

tl;dr sec is a popular, free weekly cybersecurity newsletter curated by Clint Gibler that summarizes the best application security (AppSec), cloud security, and actionable research. Designed for busy security professionals, it focuses on high-value, practical tools, and techniques rather than news-cycle hype, reaching over 90,000 readers. 
Key features of the newsletter include:

• Content Focus: Covers topics such as software supply chain security, AI-powered bug hunting, cloud-native detection engineering, and API security.
• Structure: Summarizes conference talks, technical blog posts, and new open-source tools to help professionals improve their workflows.
• Goal: The newsletter aims to act as a “too long; didn’t read” (TL;DR) for the security industry, highlighting essential information in a 7-minute read.
• Target Audience: Security engineers, application security specialists, and CISOs. 

The newsletter is published every Thursday and is widely regarded as a high-density, technical resource.