Porphyra umbilicalis occurs in the North Atlantic. In the east, it is found in Iceland and has been recorded from Norway to Portugal. In the west it is found from Labrador in Canada to Virginia, USA.
The name P. umbilicalis has been used for other species that look similar and are found in other parts of the world. However, we know from molecular studies that these are different species.
Porphyra umbilicalis is found throughout the seashore but usually grows in the upper part of the shore where it sometimes forms a distinct zone.
It is found on a wide range of hard surfaces, including bedrock, boulders, concrete, wood and on the shells of sea creatures such as limpets, mussels and barnacles.
It can also be attached to other seaweeds.