Co-access allows multiple Crossref members to register content and create DOIs for the same book content; both whole titles or individual chapters. This means that there can be multiple DOIs registered for the same book content. Prefixes must be pre-registered for Co-access in order to participate. Co-access does not require a primary depositor. For Co-access registered members, we’ll match DOI deposits with near identical metadata (for example, matching ISBNs and titles) and enter them into a Co-access relationship where matches are found between participating members. This means that Co-access enables better linking between different Crossref DOIs and gives book publishers and aggregators of book content greater flexibility to host content within a timeframe and in a location which suits them best.