The age limit to use Oslo City Bike is 18 years, unless you have a permit from your guardians, then you're able to ride from the day you turn 15 years.
The city bikes are not customized for children's seats, unfortunately.

Anyone who uses the service is obliged to follow our terms of use. It involves a lot of responsibility when you rent a bike, from the time you unlock a bike until you deliver it, you'll be responsible for it.

If you lose or destroy a city bike, you will be liable for the damages, and must replace it according to our terms of use, or according to the Norwegian Damages Act § 1 - 1 and § 1 - 2 if you are a minor.