Visas are granted for a maximum of 90 days at a time. Only in exceptional cases are applicants granted a visa for a visit of more than 90 days’ duration, but never for longer than a year.
If you need to stay longer than your visa is valid, you can apply to extend your visa or apply for a visitor's permit. If you are visa exemption and wish to stay longer than 90 days, you must apply for a visitor's permit.
Please visit the "Apply to extend your visit to Sweden" page on the Swedish Migration Agency website.