Google Chat is a communication software developed by Google built for teams that provides direct messages and team chat rooms, along with a group messaging function that allows Google Drive content sharing.
Confirm each reviewer's direct access before sending a proof.
See whether your reviewer has direct access to a proof before you ask for feedback, right in the conversation where you asked.
Return revised proofs beside the originals for approval.
See a revised image proof beside the original, with the requested changes called out. Your reviewer can approve the new version in the same thread.