This behavior changed in January 2022. ArXiV now assigns DOIs, as well as arXiv IDs. The change was supposedly made to improve discoverability, and to "help arXiv meet the ‘FAIR Guiding Principles for scientific data management and stewardship’".
Starting in January 2022, arXiv began registering DOIs and submitting associated article metadata to DataCite on behalf of (and at no cost to) arXiv authors. The first articles to receive DOIs are those with 2201.NNNNN identifiers, with all new articles receiving DOIs going forward. Following the successful launch, we will begin minting “arXiv DOIs” for the approximately 2M articles in arXiv’s corpus published between 1991 and 2021. The article abstract (/abs) pages are also now updated to display the arXiv DOIs following the registrations.
Why add DOIs when there are arXiv identifiers? Are arXiv identifiers going away?
The arXiv identifier has existed for more than 30 years; we will continue supporting it and you may use it in your citations as an alternative to the arXiv DOI. We are issuing DOIs for several reasons:
The arXiv identifier has existed for more than 30 years; we will continue supporting it and you may use it in your citations as an alternative to the arXiv DOI. We are issuing DOIs for several reasons:
Making article metadata available in DataCite’s centralized location allows research outputs to be more discoverable and harvestable.Making article metadata available in DataCite’s centralized location allows research outputs to be more discoverable and harvestable. Some funding agencies require DOIs for the research they are supporting.
Some funding agencies require DOIs for the research they are supporting.
The DOI is constructed from the ID according to
An author can determine their article’s DOI by using the DOI prefix https://doi.org/10.48550/ followed by the arXiv ID (replacing the colon with a period). For example, the arXiv ID arXiv:2202.01037 will translate to the DOI link https://doi.org/10.48550/arXiv.2202.01037