If you were born in the UK prior to 1 January 1983 then you are born British. After this date you would have to have been born to a British national or a person with settled status, meaning, Indefinite Leave to Remain or Permanent Residence.
REGISTRATION ROUTE 1:
The child is born in the UK and resides in the UK for the first 10 years of their life. In this circumstance they can usually make an application for British citizenship provided they are of ‘Good Character’ (this only applies to ten-year-old children and over) and have not been absent from the UK for too many days.
REGISTRATION ROUTE 2:
A child born in the UK that is not automatically British, if the parents are not British or settled at the time of the birth. They can however apply to become British by way of registration if one or both parents later obtain settled status or British nationality.
With this route the child will again need to show that they have good character and have been resident in the UK without exceeding the permitted absences. Again, good character needs only be shown for children who are ten years old or older.