Question about alt tags

Hello,

I am using buttons at navbar instead of links. I am wondering should i put alt tag for the navbar buttons or leave them blank?

Because they are at top of page and if i put alt tag to them, google will see alt tags of buttons instead of content.

So which one is more seo friendly?

If this is your navigation structure, then you should use the ALT text to describe them. They will not confuse alt text on your navigation links with the first text content of the page.