How to set it up
Open the website you want to use like an app. In Safari, choose File -> Add to Dock, give it a clear name, and confirm. The new web app appears in your Dock and opens like a normal Mac app.
In Chrome or Edge, open the browser menu and look for Save and share, Create shortcut, or Install app. If there is an option to open it as a separate window, turn that on.
Where it helps most
This is useful for sites you open constantly: ChatGPT, Notion, Google Calendar, Linear, Trello, WhatsApp Web, banking dashboards, or internal work tools. They get their own window and Dock icon instead of disappearing between twenty browser tabs.
It is especially good for work tools that feel like apps but do not have a strong native Mac version. You can launch them directly, switch to them with Cmd-Tab, and keep your main browser cleaner for research.
What to watch
Do not put every website in your Dock. That only moves the clutter from your browser to your Dock. Good candidates are tools you use daily, want to keep separate, and usually keep open for more than a few minutes.
If a web app behaves oddly, check whether pop-ups, saved sign-ins, or browser extensions are missing. Some sites still work better in a normal browser tab. In that case, a pinned tab is the better choice.