A DOI (Digital Object Identifier) is a persistent identifier that resolves to the current location of a resource, whereas a URL is a direct web address that points to one fixed location. The practical difference is durability: when a publisher reorganises a website, a URL can break (“link rot”), but a DOI continues to resolve because it redirects through the Handle System to wherever the content now lives. For scholarly citation, this is why DOIs are preferred over raw URLs.
How a URL works and why it rots
A URL (Uniform Resource Locator) describes where something sits on a particular server at a particular path, for example https://example.org/journal/2024/article-37.html. If the publisher migrates platforms, renames directories, or retires a section, that exact path may no longer exist and the link returns a 404 error. This decay is known as link rot; a related problem, content drift, occurs when a URL still resolves but the content behind it has changed. Both undermine the scholarly record because a citation should point readers to the exact source the author used.
How a DOI works: the Handle System
A DOI is an identifier of the form 10.xxxx/suffix assigned to a resource by a registration agency such as Crossref or DataCite. The DOI is not a location; it is a name. Resolution happens through the Handle System, a distributed identifier-resolution infrastructure. When you append a DOI to a resolver, for example https://doi.org/10.xxxx/suffix, the resolver looks up the current target URL registered for that DOI and redirects you. If the publisher moves the content and updates the DOI’s registered target, every existing citation keeps working without change. The identifier stays stable while the underlying location is free to move. The same mechanism underpins our wider work on research outputs and metadata.
DOI vs URL at a glance
| Property | DOI | URL |
|---|---|---|
| What it identifies | The object (a name) | A location (a path) |
| Persistence | High — survives site moves | Low — breaks if path changes |
| Resolution | Handle System redirect | Direct request to a server |
| Carries metadata | Yes (via registration agency) | No |
| Best for | Articles, datasets, formal records | Web pages, blogs, sites without a DOI |
How to cite with a DOI
Most current style guides ask you to present a DOI as a full, clickable link. The widely recommended display form is https://doi.org/10.xxxx/suffix rather than the bare string “doi:10.xxxx/suffix”. Place it at the end of the reference. You do not normally need to add an access date for a source with a DOI, because the identifier is stable; access dates are reserved for sources likely to change. To understand how the DOI fits into the structure of a complete reference, see our guide to what a citation is and its purpose, and the broader explainer on the DOI and Handle System resolution.
When to use a URL instead
Not everything has a DOI. Reports, web pages, blog posts, government documents and many grey-literature items are cited with a URL because no persistent identifier was ever assigned. In those cases, give the most stable URL available, add a retrieval date if the content may change, and consider linking to an archived snapshot in a web-archiving service to guard against future link rot. When a DOI is available, always prefer it. Reference managers and a sound bibliography workflow — covered in our piece on how to compile a bibliography — make it easy to capture the DOI automatically. For terminology, our research-standards dictionary defines persistent-identifier concepts precisely.
Good practice for durable links
Prefer the DOI when one exists; use the https://doi.org/ resolver form; keep raw URLs only for sources without identifiers; and archive volatile web sources. A reference manager (see our overview of reference management software) will usually pull the DOI from the source metadata, but you should always verify it resolves before you submit.
Frequently asked questions
Is a DOI a type of URL?
No. A DOI is an identifier — a name for an object. It becomes clickable when you prefix it with a resolver such as https://doi.org/, which turns the name into a link that redirects to the object’s current location.
Why does my old citation’s DOI still work after the journal changed websites?
Because the DOI resolves through the Handle System to whatever target URL the publisher has registered. When the site moved, the publisher updated that target, so the DOI keeps pointing at the right place even though the underlying URL changed.
Should I include both the DOI and the URL?
Generally no — if a DOI exists, cite the DOI and omit the raw URL, because the DOI is the more durable and authoritative link. Use a plain URL only when the source has no DOI.
Do DOIs guarantee a source will never disappear?
A DOI guarantees stable resolution as long as the registrant maintains it, but it cannot stop a publisher from withdrawing content. For volatile or unregistered sources, archiving a snapshot remains good practice.
