Abstract: The present invention provides a holder for a planar data storage medium, comprising a first opening through which the planar data storage medium is insertable into a storage area of the holder in an insertion direction within the plane of the planar data storage medium. Further, a retaining mechanism is provided which is resiliently biased to resist removal of the planar data storage medium from the storage area in a direction opposite to the insertion direction. However, the holder is configured to enable a pressure to be applied to the planar data storage medium to overcome the bias of the retaining mechanism, thereby allowing the planar data storage medium to be removed via the first opening in the holder. This approach enables the holder of the present invention to have a simpler construction and a significantly thinner profile than typical prior art holders.