I can't open your project to double check, but I can get the same results in your chat if I disable the CSS for .container

Both the header and the body contents have container but the body ALSO has mx-auto, which means it'll still have automatic horizontal margins to center itself, even without the container class, which is why it doesn't seem to be affected

The container class is generated by tailwind based on this configuration, so that's where I'd look for discrepancies. Check the one in v0 and the local one to see what styles are applied to container

https://v3.tailwindcss.com/docs/container

Thank you for the suggestion. What seems to work in my case was to apply the mx-auto class to the header.