What Does It Mean for a Journal to Be Indexed?

“Indexed journal” and “indexing journal” are two phrasings of the same underlying question researchers, editors, and research administrators keep running into: what does it actually mean for a journal to be indexed, and by whom? The honest answer is that “indexed” is not one thing — it is shorthand for “this journal met the published inclusion criteria of a specific database,” and those criteria differ meaningfully across Scopus, Web of Science, PubMed/MEDLINE, and DOAJ. This guide covers what indexing means, why it matters for discoverability and perceived legitimacy, each major database’s real published criteria, and how indexing status relates to — but is not the same thing as — a journal’s impact factor or other bibliometric rankings.

What it means for a journal to be “indexed”

A bibliographic database “indexes” a journal when it systematically catalogs that journal’s articles — title, authors, abstract, and (for some databases) controlled-vocabulary subject terms and full reference lists — on an ongoing, article-by-article basis, making them discoverable through the database’s search interface. Indexing is a database’s decision, made against that database’s own published evaluation criteria; it is not something a journal or publisher can simply claim or purchase. Two distinctions worth holding onto before comparing databases:

Indexing is not the same as being cited or ranked. A database can index a journal’s content without that journal receiving a citation-based score like a Journal Impact Factor — indexing is about inclusion and discoverability; bibliometric ranking is a separate, downstream calculation some (not all) indexing databases also produce. See the section below on how the two relate.
“Indexed in Google Scholar” is not a meaningful claim. Google Scholar has no published inclusion criteria, no application process, and no editorial review — it crawls and algorithmically parses scholarly-looking web content automatically. Almost any journal with a functioning website, including predatory ones, will appear in Google Scholar. Treat “indexed in Google Scholar” on a journal’s own marketing as informative about nothing; it is a common predatory journal red flag precisely because it sounds like a credential but isn’t one. For more on spotting that pattern, see CASRAI’s guide on how to identify predatory journals and publishers.

Why journal indexing matters

Three practical consequences follow from a journal actually clearing a real database’s inclusion bar:

Discoverability. Researchers overwhelmingly search within a small number of databases (PubMed for biomedicine, Scopus and Web of Science across disciplines) rather than the open web. A journal outside those databases is effectively invisible to most literature searches in its field, regardless of the quality of any individual article in it.
A legitimacy and prestige signal. Because each database enforces its own published editorial and technical bar (detailed below), inclusion functions as third-party validation that a journal meets a baseline of editorial process, publishing regularity, and technical standards — which is exactly why predatory publishers routinely misrepresent their indexing status, and why verifying a specific claim directly against the database (not the journal’s own website) matters.
Tenure, promotion, and funder relevance, in some contexts. Some institutional tenure/promotion committees and some funders use indexing status (particularly Web of Science Core Collection or Scopus inclusion) as one input among several when evaluating a researcher’s publication record or a journal’s standing — though practice varies widely by institution, discipline, and country, and indexing status alone is a weak proxy for research quality on its own. Where a citation-based metric matters more directly than raw inclusion, that is the Journal Impact Factor question covered separately below.

The major indexing databases and their real inclusion criteria

The four databases researchers ask about most often evaluate journals on genuinely different criteria, run by different organizations, for different purposes. Treating them interchangeably (“is this journal indexed?” without specifying where) is the single most common source of confusion.

Scopus (Elsevier)

Scopus journal selection is run by the Content Selection and Advisory Board (CSAB), an independent panel of subject-matter experts formed in 2009. Before a title even reaches CSAB review, it must clear technical prerequisites: peer-reviewed content with a publicly described peer-review process, a registered ISSN, and regular publication. CSAB then evaluates surviving candidates against five published categories:

Journal policy — a convincing editorial approach, the type of peer review used, and geographic diversity among both editors and authors.
Content — the quality and clarity of published research and abstracts, and how well content matches the journal’s stated aims and scope.
Journal standing — citation impact of the journal’s articles within Scopus itself, and the editor’s professional standing.
Regularity of publication — no delays or interruptions to the publication schedule.
Online availability — full content available online, an English-language homepage, and professional web presentation.

Elsevier itself reports that of the thousands of new titles suggested for Scopus each year, only about a third clear the technical prerequisites, and roughly half of those are ultimately accepted by CSAB — a real acceptance rate well under 20% of everything initially proposed. Source: Elsevier, Scopus content policy and selection; Scopus Content Selection and Advisory Board.

Web of Science Core Collection (Clarivate)

Clarivate’s in-house editors — deliberately unaffiliated with any publishing house, to remove conflicts of interest — evaluate journals against a published set of 28 criteria split into two tiers. The first tier, 24 quality criteria, screens for editorial rigor and best practice: external peer review of primary research articles, clear editorial board and affiliation information, content matching the journal’s stated scope, adherence to publication ethics, and basic production standards. A journal that meets all 24 quality criteria is admitted to the Emerging Sources Citation Index (ESCI).

The second tier, 4 impact criteria, is assessed on top of the quality criteria and is based primarily on citation activity — comparative citation performance, citation patterns of the editorial board, and the content’s significance to its field. Only journals meeting both tiers advance to one of the “flagship” citation indexes — Science Citation Index Expanded (SCIE), Social Sciences Citation Index (SSCI), or Arts & Humanities Citation Index (AHCI), depending on subject area — which together with ESCI make up the Web of Science Core Collection. Placement is not permanent in either direction: an ESCI journal that gains sustained citation impact can move up to a flagship index, and a flagship-index journal whose impact declines can move down to ESCI. This two-tier structure is also why “Web of Science indexed” is itself an ambiguous claim — ESCI inclusion and SCIE/SSCI/AHCI inclusion are different achievements, and only the latter carries a Clarivate-calculated Journal Impact Factor (see the section below). Source: Clarivate, journal evaluation process and selection criteria. For a side-by-side of Web of Science against Scopus and OpenAlex, see CASRAI’s comparison, Scopus vs Web of Science vs OpenAlex.

PubMed and MEDLINE (National Library of Medicine) — not the same thing

This is one of the more consistently confused indexing questions, because PubMed and MEDLINE are frequently used interchangeably even though they are not the same database. MEDLINE is the National Library of Medicine’s highly selective, curated biomedical citation database, in continuous operation since the 1960s and covering several thousand selected journals; MEDLINE content is the only content indexed with NLM’s controlled vocabulary, Medical Subject Headings (MeSH). PubMed is NLM’s free public search interface, and it is broader than MEDLINE alone: it includes MEDLINE citations, but also content deposited in PubMed Central (PMC) that comes from journals never evaluated for, or not accepted into, MEDLINE, plus NCBI Bookshelf content and other NLM material. A basic PubMed record can therefore exist for an article whose journal is not, and will never be, MEDLINE-indexed — so “this journal is in PubMed” and “this journal is MEDLINE-indexed” are genuinely different claims, and only the second implies NLM editorial review of the journal itself.

NLM’s own current process (as of a 2025 restructuring) evaluates journals directly against five published elements: scope and coverage, editorial policies and peer-review transparency, scientific and methodological rigor, production/administration quality, and overall impact on the field, with at least two external consultants (typically a subject-matter researcher and a medical librarian) reviewing recent issues of each applicant journal. A significant structural change is worth flagging for anyone researching this: the Literature Selection Technical Review Committee (LSTRC) — the federal advisory committee that had reviewed MEDLINE applicants and made inclusion recommendations to NLM since 1987 — was terminated in 2025. NLM has stated it is reviewing its journal-selection processes to improve transparency and operational efficiency while maintaining its scientific and editorial standards, with further detail to follow; anyone relying on this for a formal submission should check NLM’s current guidance directly rather than older secondary descriptions of the LSTRC-era process. Sources: NLM, Journal Selection for MEDLINE; NLM, About the LSTRC; NLM Technical Bulletin, journal selection process review.

DOAJ (Directory of Open Access Journals)

DOAJ evaluates a fundamentally different thing than the three databases above: it is not a citation or discovery database first, it is a curated quality whitelist of open access journals, and its criteria are correspondingly open-access-specific rather than citation- or impact-based. To be accepted, a journal must, among other published requirements:

Be genuinely open access — full text of all content freely available immediately, with no embargo, registration wall, or paywall (a paid print edition is allowed alongside a free online edition);
Have a registered ISSN matching the title listed at issn.org, a dedicated website with a stable URL, and individually addressable article pages;
Have a named editor and editorial board with affiliations publicly listed on the site;
Run all content through a described quality-control (peer review) process, disclosed on the website;
Publish at least five research articles per year, and (for newer titles) show at least one year of continuous open-access publishing or at least ten published open-access articles before applying;
Clearly state licensing terms — DOAJ recommends Creative Commons licensing — and copyright information;
Keep editorial self-publishing in check: no more than 25% of a journal’s published papers in either of its most recent two issues can have an author who is also an editor, editorial board member, or reviewer of that journal.

Sources: DOAJ, Guide to applying; DOAJ Blog, basic criteria in plain English. DOAJ retired its separate “DOAJ Seal” quality mark in March 2025 in favor of individual, more specific labels — see CASRAI’s dictionary entry on DOAJ metadata submission for the related technical side of DOAJ participation.

Indexing vs. impact factor: related, but not the same question

“Is this journal indexed?” and “what is this journal’s impact factor?” are related but distinct questions, and conflating them is a common source of confusion:

Indexing is a yes/no inclusion decision by a specific database, against that database’s own published criteria (above). A journal is either indexed in Scopus, or it isn’t; either MEDLINE-indexed, or it isn’t.
The Journal Impact Factor is a citation-based number, calculated annually by Clarivate for journals in specific parts of the Web of Science Core Collection (currently SCIE, SSCI, and AHCI — not ESCI). Being Web of Science–indexed at the ESCI level does not, by itself, give a journal a Journal Impact Factor; a journal has to additionally clear Clarivate’s 4 impact criteria to reach an index that carries one.
Scopus does not publish an “impact factor” at all — it produces its own separate citation metrics (such as CiteScore), calculated differently from Clarivate’s JIF. A journal can be well indexed in Scopus and have no Journal Impact Factor whatsoever, because JIF is specifically a Clarivate/Web of Science product.

For the mechanics of the Impact Factor itself — its formula, history, and what it can and can’t legitimately support — see CASRAI’s dedicated coverage rather than duplicating it here: the dictionary entry on the Journal Impact Factor (JIF), and the practical guides How to Look Up a Journal’s Impact Factor and Journal Impact Factor and Quartile Rankings.

How to check whether a specific journal is indexed

Because indexing status is a claim about a specific database, verify it directly against that database rather than trusting a journal’s own website:

Scopus: search the journal title in Scopus’s Source list (Sources search on scopus.com, or the publicly browsable Scopus Sources tool), which lists currently and formerly indexed titles.
Web of Science: use Clarivate’s Master Journal List (mjl.clarivate.com) to look up a title and see which specific index (ESCI, SCIE, SSCI, or AHCI) it sits in — not just whether it appears at all.
MEDLINE: search the NLM Catalog (not PubMed itself) and filter to “currently indexed for MEDLINE,” since a journal can otherwise appear in PubMed via PMC without being MEDLINE-indexed, as covered above.
DOAJ: search the journal directly on doaj.org — DOAJ only lists journals it has actively vetted and accepted.

A journal claiming indexing status that does not show up in the relevant database’s own lookup tool is a specific, checkable warning sign, not a technicality — see the predatory-journal guide linked above for how this fits into a broader publisher-vetting workflow.

Frequently asked questions

What does it mean when a journal is described as “indexed”?

It means a specific database (Scopus, Web of Science, MEDLINE, DOAJ, or another) has evaluated the journal against its own published criteria and accepted it for ongoing, systematic inclusion. “Indexed” without naming the database is an incomplete claim — always ask “indexed where?”

Is being in PubMed the same as being MEDLINE-indexed?

No. PubMed is broader than MEDLINE: it also includes PubMed Central deposits from journals that were never evaluated for, or were not accepted into, MEDLINE. Confirm MEDLINE status specifically via the NLM Catalog, not by finding the journal in a PubMed search.

Does an indexed journal automatically have a Journal Impact Factor?

No. A Journal Impact Factor is calculated by Clarivate only for journals in the flagship parts of the Web of Science Core Collection (SCIE, SSCI, AHCI) — not for journals indexed only in ESCI, and not for journals indexed in Scopus, MEDLINE, or DOAJ, none of which produce a Journal Impact Factor themselves.

Can a journal be genuinely Scopus- or Web of Science–indexed and still be a poor publishing choice?

Indexing in a reputable database is a real, verifiable baseline, but it is not a guarantee of quality for every individual article, and indexed journals have occasionally been removed for declining editorial standards (Web of Science and Scopus both periodically re-review and delist titles). Indexing status is one signal among several — not a complete substitute for evaluating a specific journal’s editorial practices directly.

Is “indexed in Google Scholar” a meaningful credential?

No. Google Scholar has no application process, published criteria, or editorial review — it algorithmically crawls scholarly-looking web content, and nearly any journal with a working website will appear in it, including predatory ones. Treat this claim on a journal’s marketing materials as uninformative.

What’s the difference between the Web of Science Core Collection and the Emerging Sources Citation Index?

ESCI is one part of the Web of Science Core Collection — the entry point for journals meeting Clarivate’s 24 quality criteria but not (yet, or no longer) its 4 additional impact criteria. SCIE, SSCI, and AHCI are the more selective “flagship” indexes within the same Core Collection, reserved for journals meeting both sets of criteria, and only journals in those flagship indexes receive a Journal Impact Factor.

How do I verify a journal’s indexing claim myself, rather than trusting its website?

Search the journal directly in the relevant database’s own public lookup tool: Scopus Sources, Clarivate’s Master Journal List, the NLM Catalog (filtered to MEDLINE-indexed), or doaj.org. Each is free to search and is the authoritative record — a discrepancy between a journal’s own claim and what the database’s lookup tool shows is a genuine red flag.