"Is the journal indexed?" sounds like a yes-or-no question. It is not. Scopus, Web of Science, PubMed, MEDLINE and PubMed Central are run by different organisations, admit content through different routes and do different jobs. Treating them as interchangeable leads authors to misread a journal's standing and leads editors to make the wrong application to the wrong body.
The confusion is understandable. The same names appear side by side on journal websites, in promotion criteria and in funder guidance, and some of them overlap: MEDLINE sits inside PubMed, PubMed links to PubMed Central, and Web of Science supplies the data behind the Journal Impact Factor. But each service has its own owner, its own selection process and its own definition of what "in" means.
This explainer sets out what each service is, how journals get in, and what inclusion does and does not tell you. For the practical question of how to test a claim printed on a journal's own website, see our companion guide, What Does "Indexed" Really Mean on a Journal Website?.
Scopus: Elsevier's curated citation database
Scopus is an abstract and citation database owned by Elsevier. It covers journals, book series and conference proceedings across the sciences, social sciences and humanities, and it is the data source for CiteScore, Elsevier's journal citation metric.
Titles are selected by the Content Selection and Advisory Board (CSAB), which Elsevier describes as an independent board of international subject experts. A journal must first meet technical requirements, then it is assessed in five areas: journal policy, content, journal standing, publishing regularity and online availability.
Selection is not permanent. Scopus runs a continuous re-evaluation programme. Titles can be flagged because the research community raises concerns about publication standards, or because an Elsevier data model detects outlier behaviour in publication volumes, citations or authorship patterns. Flagged titles are reviewed by the CSAB against the same criteria used for new titles. When a journal is discontinued, Elsevier's policy is that content already indexed generally stays in the database as part of the scientific record, while new content stops being added. The reasons and consequences are covered in depth in Why Do Journals Lose Indexing?.
Web of Science Core Collection and the impact factor
Web of Science is Clarivate's citation database. Its Core Collection is the part most often meant when people say a journal is "in Web of Science", and for journals it comprises four indexes: the Science Citation Index Expanded (SCIE), the Social Sciences Citation Index (SSCI), the Arts & Humanities Citation Index (AHCI) and the Emerging Sources Citation Index (ESCI).
Clarivate selects journals through an in-house editorial team that it says has no affiliation to publishers or research institutions. Journals are assessed against 28 criteria: 24 quality criteria covering editorial rigour and publishing practice, and four impact criteria based largely on citation activity. Journals that meet the quality criteria enter ESCI; those that also meet the impact criteria are placed in SCIE, SSCI or AHCI according to subject. ESCI is therefore not an unvetted waiting room, but nor is it the same as SCIE. Clarivate also reserves the right to remove journals that no longer meet its standards, and says this can extend to content already indexed.
The Journal Impact Factor is a separate thing again. It is a metric published in Clarivate's Journal Citation Reports (JCR), calculated from Web of Science data. It is not an index and not a form of coverage. Before the 2023 JCR release only SCIE and SSCI journals received one; since then, every journal in the Core Collection, including AHCI and ESCI titles, has been eligible for a JIF, displayed to one decimal place. A journal that says it "has an impact factor" is therefore telling you it is in the Core Collection, but not which index. For what the number can and cannot tell you, see Is the Impact Factor Losing Its Power—or Are We Using It Wrong?.
PubMed, MEDLINE and PubMed Central
The three services run by the US National Library of Medicine (NLM) cause the most confusion, because they are nested.
PubMed is a free search interface and citation database for the biomedical and life sciences. NLM describes it as encompassing three components: MEDLINE, PubMed Central and the NCBI Bookshelf. PubMed holds citations and abstracts, not full text. Publishers cannot apply to "PubMed" as such; content arrives because a journal has been accepted into MEDLINE or PMC, or because articles are deposited through a funder route.
MEDLINE is NLM's selective bibliographic database and the largest component of PubMed. Its records are indexed with NLM's Medical Subject Headings (MeSH), the controlled vocabulary that makes precise biomedical searching possible. NLM says MEDLINE contains references from more than 5,200 journals. Inclusion is decided by NLM, which assesses scope and coverage, editorial policies, scientific rigour, production and impact. For almost four decades NLM was advised by the Literature Selection Technical Review Committee, a federal advisory committee established in 1987; NLM states that the committee was terminated in 2025, and its current application pages describe a review carried out by NLM. Applicants need, among other things, an ISSN, at least 12 months of publication and at least 40 peer-reviewed articles.
PubMed Central (PMC) is a free full-text archive. Journals join through agreements with NLM, and author manuscripts arrive through funder mandates such as the NIH public access policy. Being in PMC is not the same as being indexed for MEDLINE: the two have separate application and evaluation processes. NLM's own FAQ warns that finding an individual article in PubMed does not mean its journal is in MEDLINE or PMC.
DOAJ and Google Scholar
Two other names often appear in the same lists. The Directory of Open Access Journals (DOAJ) is a curated directory of peer-reviewed open access journals. It checks licensing, editorial transparency, peer review and other practices, but it is not a citation database and produces no impact metric. Google Scholar is a search engine. It discovers scholarly content automatically through crawlers that follow technical guidelines; there is no application, and its documentation describes technical and content-type requirements rather than an editorial judgement about journal quality. Appearing in Google Scholar shows that a site is crawlable, nothing more.
What inclusion does and does not mean
Inclusion in a selective database means a journal passed that organisation's review at a point in time and has not since been removed. It is a useful signal of basic editorial standards, and many institutions build it into hiring, promotion and funding rules.
It does not certify every article, and it is not a single universal status. A journal can be in Scopus and not in Web of Science, in ESCI and not in SCIE, in PMC and not in MEDLINE. Coverage also has dates: a database may cover only some years of a journal's run, and a discontinued title remains visible for its earlier volumes. None of these services are interchangeable with discovery tools, archiving services or citation metrics, even when the same company runs several of them.
How to check status at the source
The authoritative answer always comes from the database owner, searched by ISSN rather than title:
- Scopus: Elsevier's downloadable source title list, linked from its content policy page and reissued several times a year, records active titles, coverage years and discontinued titles; subscribers can also use the Scopus Sources browser.
- Web of Science: Clarivate's Master Journal List shows whether a journal is currently covered and in which Core Collection index.
- MEDLINE and PMC: the NLM Catalog record shows a journal's "Current Indexing Status" for MEDLINE and the years it was indexed; PMC participation is listed separately.
- DOAJ: the journal's entry on doaj.org.
Conclusion
The precise question is never "is it indexed?" but "indexed where, in which collection, and for which years?" Scopus and Web of Science are competing curated citation databases with their own selection boards. The impact factor is a Clarivate metric, not a form of indexing. PubMed is a search interface; MEDLINE is NLM's selective MeSH-indexed subset; PMC is a full-text archive. DOAJ is a directory, and Google Scholar is a crawler. Authors, editors and assessment committees that keep these distinctions straight, and check each one at the source, will make better decisions than those who treat "indexed" as a badge.
