One or more embodiments of a thumbnail caching system dynamically provide a thumbnail cache of digital content items (e.g., photos, videos, audio) to a user on a client device. In particular, the thumbnail caching system provides a thumbnail cache of a digital content collection to a client device such that the thumbnail cache does not exceed a threshold storage limit for the client device. In addition, the thumbnail caching system intelligently adjusts the thumbnails within the thumbnail cache to keep the size of the thumbnail cache within the threshold storage limit irrespective of the number of digital content items stored or added to the digital content collection. Further, the thumbnail caching system can dynamically adjust the size of the thumbnail cache in response to a user adding or removing external data to the client device.