I run a totally different stack, but by my count there at least 8 technologies that I use in most every web app (HTML, CSS, Javascript, a backend language, a fr

I run a totally different stack, but by my count there at least 8 technologies that I use in most every web app (HTML, CSS, Javascript, a backend language, a front and/or backend framework, a relational database, NGINX, Linux). And that does not include domain specific technologies, or general skills like image editing, design, application architecture, etc. needed to create a functional app. Edit: 9 since you specified ssl too (thank you Let's Encrypt), and 10 for real-time support, and 11-20 for all the devops stuff that I should know more about.