Making mortgage repayments weekly or fortnightly rather than monthly can save you interest.
By switching to weekly or fortnightly repayments, you end up making more repayments each year. There are 26 fortnights in a year, which is equivalent to 13 monthly repayments.
Additionally, since interest is often calculated daily, making more frequent repayments reducing the principal more regularly, potentially saving you a small amount of interest each month.