Ziflow - Online Proofing software from Ziflow keeps teams connected and collaborating by providing a single source of truth for creative review and approval.
Abstract - A secure, version-controlled hub for your design files
GoVisually - GoVisually empowers creative teams to deliver better designs, by providing a simple way to review and approve designs quickly and easily
Kactus - Design version control without changing your tools
PageProof - Online proofing of anything and everything, made simple. Streamline feedback for easy collaboration, secure workflows, and faster approvals. PageProof. The smarter way to review.
Git Sketch Plugin - Version control for designers