HTML Cause hydration failed because the initial UI does not match what was rendered on the server?

Simply adding: <html lang='pt-br'>

to my component in _app.tsx

const Layout = (props: ILayoutProps) => {
return (
  <html lang='pt-br'>
        <div className={`${inter.className} layout`}>
          <div className='w-full h-full flex flex-col justify-between'>
              <Left>
                {children}
              </Left>
              <Footer />
          </div>
        </div>
        </html>
  )
}

I get the error:

Unhandled Runtime Error
Error: Hydration failed because the initial UI does not match what was rendered on the server.

Warning: Expected server HTML to contain a matching <html> in <div>.

See more info here: https://nextjs.org/docs/messages/react-hydration-error

Why is that? Why is even different from server? Do I need to compile anything? But simply removing it, make the page work again. This is the main thing used in _app.tsx component.