Popular options for preprints.

Free: Can preprints be submitted for free. Comments: Support for online comments. Private: Support for private preprints. Peer-Reviewed: Whether the preprints are peer-reviewed on the server. DOI: Each item is assigned a unique digital object identifier. Version-Control: Is the preprint stored using a version-control system with the complete history of modifications? Other content: Can upload figures, videos, datasets, code.