Does the extra one pays on their mortgage go directly towards principle?

I know that, more-so towards the beginning of a mortgage, a large amount of one's payments just go towards interest. So say, for example, my mortgage is $1,000 a month. If I pay $1,100 dollars a month does that extra $100 go completely towards principle or does it also mostly go towards interest?

Read more: Does the extra one pays on their mortgage go directly towards principle?