Methods and systems are described for identifying and marking content items that have or have not been shared to social media or content hosting services. The methods and systems use a marking engine to access a content item in a content library and identify the content hosts or social media sites to which the content item was previously transmitted. A marking engine may create a user interface, generate a thumbnail of each content item, and generate a graphical indicator for each identified content host. A marking engine may generate for display thumbnail representations of each content item with graphical indicators of each of the identified content hosts. A marking engine may sort thumbnails by metadata associated with the corresponding content items, such as creation time and date, location, share status, and other classifications and filters, to indicate which content items are ready to be shared to a content host.