Online Proofing platforms operationalize the visual review and approval workflow for creative assets — images, videos, PDFs, and marketing collateral — with click-to-comment annotation, side-by-side version comparison, and structured sign-off routing. The category exists distinct from broader Marketing Work Management because pure-play proofing tools serve a specific job at a different price point and granularity. Core capabilities include click-to-comment annotation across formats, version comparison with markup history, multi-stakeholder approval routing, audit-trail documentation, and creative-tool integrations. The market is led by pure-play proofing platforms (Filestage, Ziflow, PageProof, GoVisually, ReviewStudio) and Adobe-owned video proofing (Frame.io).