I have been using Chrome's official MCP devtools server since Nov 2025.

https://github.com/ChromeDevTools/chrome-devtools-mcp

Before that I used Chrome web drivers but MCP is faster and more capable.

I also instruct LLMs to test my pages on Firefox using its official MCP to make sure they work in Firefox too:

https://github.com/mozilla/firefox-devtools-mcp

Now I will add Safari to the compatibility tests. cool