Open Access

There are many ways to define Open Access. OpenAlex uses a broad one: a work is OA if there’s a URL where you can read its full text without paying money or logging in. Of the roughly 322 million works in OpenAlex, about 121 million (37%) are Open Access by this definition.

For each work, OpenAlex decides whether it meets the definition using several techniques — checking whether its journal is in the Directory of Open Access Journals (DOAJ), looking for a free copy on the publisher’s page, and searching repositories for deposited versions. When a work is OA, OpenAlex gives you a link to its full text.

On the Work object, this information lives in the open_access object:

OA statuses

Beyond the yes/no of is_oa, OpenAlex assigns every work an OA status — the “colors” widely used in OA research and policy:

Two things follow from these definitions that often surprise people:

• Status depends on the journal, not just the article. The same freely readable article is gold (or diamond) in a fully-OA journal but hybrid or bronze in a toll-access one. How OpenAlex determines whether a journal is fully OA — including journals that “flipped” to OA partway through their run — is covered in Journal quality & OA status.
• The hybrid/bronze line is drawn by license. A free-to-read article in a toll-access journal is hybrid if it carries an open license and bronze if it doesn’t. What counts as an open license is defined below.

You can filter and group works by status — for example, group all works by oa_status — so the taxonomy is countable, not just descriptive.

OA locations

A work’s OA evidence lives in its locations — the individual places (journal pages, repositories) where copies of the work are hosted. Each location records whether that copy is OA (is_oa), plus its landing_page_url, pdf_url, license, version, and host source.

What counts as an OA location? OpenAlex is flexible: in general, if a page makes the full text of an article available for free — directly on the page, through a PDF link, or in an embedded reader — it counts. There are two deliberate exceptions, both about keeping links usable and machine-readable:

• Sites requiring registration. ResearchGate, a well-known academic social network, requires login before reading. OpenAlex already excludes it to stay on the right side of publishing agreements, but the registration wall would be a deal-breaker on its own.
• Sites gated by CAPTCHAs. These make it hard for automated systems to verify that full text is really there, and make the links less useful — you never know whether a request will return the article or a puzzle. SSRN hosts many articles OpenAlex would love to include, but it prompts for CAPTCHAs and accounts after a few downloads.

Publisher-hosted vs. repository-hosted. Locations broadly split into two kinds, visible via the location’s source.type. A publisher-hosted location is provided by the work’s original publisher through its canonical URL, as a published or accepted version. A repository location is a copy in an OA repository — most commonly an institutional repository run by a university library, or a subject repository like PubMed Central or arXiv. One edge case: preprint servers count as repositories, even when the preprint is the only, final version of the document — a work whose DOI points to Research Square or bioRxiv still has a repository-hosted location, not a publisher-hosted one.

The best OA location

When a work has more than one OA location, OpenAlex designates the most current, authoritative one as best_oa_location. Locations are ranked by a series of tiebreakers, in order:

1. Host kind: publisher-hosted beats repository-hosted.
2. Version: publishedVersion beats acceptedVersion, which beats submittedVersion.
3. Direct PDF link: a location with a pdf_url beats one without.
4. Match quality (repository locations): a repository record matched to the work by DOI beats one matched by title.
5. Repository rankings: some major repositories, like PubMed Central and arXiv, rank above others.

The oa_url on the work’s open_access object is the URL of this best location.

Licenses

There are many definitions of what constitutes an OA license — BOAI, SPARC, and others (see this literature review for a fuller list). OpenAlex’s job is not to decide which definition is “truly” open, but to collect the data users need to make their own decisions: each location carries the license OpenAlex found for that copy, or null if none was found.

For the purposes it does need a definition for — chiefly drawing the hybrid/bronze line — OpenAlex errs toward inclusiveness: the cutoff for “is this license open” is deliberately low, and even relatively restrictive licenses like CC-BY-NC-ND count. Downstream users who need a stricter standard (for example, funders that mandate CC-BY) can filter on the license values themselves.

Licenses OpenAlex counts as open include:

• Any Creative Commons license
• Public domain / CC0
• Publisher-specific open licenses such as ACS Editors’ Choice and the APS accepted-manuscript license
• Many less-common licenses, as long as they grant users sufficient rights to freely use and redistribute content

Licenses OpenAlex recognizes but does not count as open include the Elsevier user license, which doesn’t allow redistribution. Expect these lists to grow and change.

One pseudo-license to know about: implied-oa marks articles that the publisher labels as Open Access — typically under an APC-funded hybrid arrangement — but that carry no specific license statement OpenAlex can identify.

OA dates

OpenAlex’s underlying data also tracks when a copy of a work first became available at each location. This oa_date field is exposed through the Unpaywall API format (a legacy-compatible view of the same OpenAlex data — see its data-format reference) rather than on the OpenAlex work object itself. In brief:

• Gold/diamond: the article was free from day one, so oa_date is the publication date.
• Hybrid: the publication date, or the manuscript license’s effective date if a manuscript version was opened separately.
• Bronze: always null — bronze availability can come and go, is often discovered late, and is rarely relevant to OA mandates.
• Repository copies: the date OpenAlex first observed full text there, derived from OAI-PMH record timestamps. Because raw timestamps can both pre- and post-date the actual posting, OpenAlex freezes the timestamp at first discovery; reliable dates exist only for copies first observed on or after 2020-08-07, and earlier copies get null.

Article processing charges

The article processing charge (APC) is the fee some journals charge authors to make a work OA — relevant to gold and hybrid works. OpenAlex estimates APCs at both the work level (apc_list, apc_paid) and the source level. Where that data comes from, its limitations, and how to estimate an institution’s APC spend are covered in Journal quality & OA status.

Related pages

• Journal quality & OA status — how fully-OA journals are identified, flipped journals, and APC data
• Versions — submitted, accepted, and published versions and how they interact with OA
• Sources — how works connect to journals and repositories through locations
• Works API reference — the open_access and location objects
• Why is this publication labeled as ‘closed’ when it is clearly Open Access?