TL;DR Crossref discourages our members from using DOI-like strings or fake DOIs.  Details Recently we have seen quite a bit of debate around the use of so-called “fake-DOIs.” We have also been quoted as saying that we discourage the use of “fake DOIs” or “DOI-like strings”. This post outlines some of the cases in which we’ve seen fake DOIs used and why we recommend against doing so. Using DOI-like strings as internal identifiers Some of our members use DOI-like strings as internal identifiers for their manuscript tracking systems.