Web of Science

Web of Science is Clarivate’s citation-indexing and research-discovery platform, not a single index in its own right. A publication counts as covered by Web of Science only once it has been evaluated and accepted into at least one of the platform’s underlying citation indices — most often the Science Citation Index Expanded, Social Sciences Citation Index, or Arts & Humanities Citation Index within the Web of Science Core Collection, or one of the platform’s regional indices — each governed by its own independent Clarivate selection criteria; being published, or indexed elsewhere such as in Scopus, does not automatically make a title searchable on Web of Science.

ByCASRAI Editorial Board

· Last updated 17 Jul 2026

Worked examples

Is an instance

A chemistry journal accepted into the Science Citation Index Expanded (SCIE) becomes searchable within Web of Science, and its cited references are added to the Web of Science citation graph used to calculate the Journal Impact Factor.

Is an instance

A Latin American journal never evaluated for SCIE, but accepted into the SciELO Citation Index, is still searchable within Web of Science — SciELO Citation Index is one of the platform's regional indices, distinct from (and evaluated separately to) the six Core Collection indices.

Looks similar, but isn't

Not an instance

A journal indexed only in Scopus, with no separate Clarivate evaluation, does not automatically appear on Web of Science — Scopus (Elsevier) and Web of Science (Clarivate) are run by different companies with independent, unrelated selection committees.

Not an instance

Calling a title "SCIE-indexed" is not the same claim as calling it "Web of Science-indexed" generally — SCIE is one of six Core Collection indices within the broader Web of Science platform, which also includes separately-curated regional and specialty indices a title could be covered by instead.

What Web of Science is

Web of Science is a citation-indexing and research-discovery platform owned and operated by Clarivate — not a single index and not a journal list in its own right. Searching Web of Science means searching across a bundle of separately curated citation indices that Clarivate hosts on one platform, each with its own editorial-selection criteria and scope. In practice this means a claim that a journal is “in Web of Science” is only precise once it names which underlying index accepted it — most often the Science Citation Index Expanded (SCI/SCIE), but Web of Science also spans the Social Sciences Citation Index, the Arts & Humanities Citation Index, and the regional and specialty indices described below.

Platform structure: the Core Collection, plus regional and specialty indices

The Web of Science Core Collection is the platform’s central bundle of six citation indices:

Science Citation Index Expanded (SCIE) — sciences, with backfile coverage to 1900
Social Sciences Citation Index (SSCI) — social sciences, with backfile coverage to 1900
Arts & Humanities Citation Index (AHCI) — arts and humanities
Emerging Sources Citation Index (ESCI) — journals under evaluation that don’t yet meet full SCIE/SSCI/AHCI criteria
Conference Proceedings Citation Index (CPCI) — indexed conference literature
Book Citation Index (BCI) — scholarly books

Beyond the Core Collection, Clarivate has progressively added regional citation indices to the same platform, extending coverage into scholarship the Core Collection’s selection criteria have historically underrepresented: the Chinese Science Citation Database (added 2008, produced with the Chinese Academy of Sciences), the SciELO Citation Index (2013, covering Brazil and other Latin American countries, Spain, Portugal, the Caribbean, and South Africa), the Korea Citation Index (2014), the Russian Science Citation Index (2015), and the Arabic Citation Index (2020, launched with the Egyptian Knowledge Bank). The platform also carries specialty databases layered on top of these — including BIOSIS, Zoological Record, the Data Citation Index, and the Preprint Citation Index — and, for many subscribing institutions, MEDLINE search within the same interface. A given institution’s actual Web of Science access varies with which of these indices its license covers, so “covered by Web of Science” is not one fixed scope across every subscriber.

From “Web of Knowledge” to “Web of Science”

The platform’s current name is more recent than the underlying index. The online successor to the print Science Citation Index launched in 2002 as ISI Web of Knowledge, under the Institute for Scientific Information / Thomson Corporation. After Thomson Corporation and Reuters merged in 2008, the platform continued under “Thomson Reuters Web of Knowledge” branding. Thomson Reuters renamed the platform Web of Science in January 2014 — the name it has carried since, through the 2016 spin-out and sale of Thomson Reuters’ Intellectual Property & Science business (rebranded Clarivate Analytics, now Clarivate) that made Clarivate the platform’s current owner and operator. A citation, library guide, or older paper that refers to “Web of Knowledge” is describing the same underlying platform under its pre-2014 name, not a different product.

Web of Science vs. the indices within it

“Web of Science” and “Science Citation Index” are related but not interchangeable terms. The Science Citation Index / SCI Expanded is one citation index — the platform’s oldest and largest — that sits inside the Web of Science Core Collection; it is a component of the platform, not a synonym for it. A journal can accurately be described as “Web of Science-indexed” while covered only by a regional or specialty index, without ever having been evaluated for SCIE at all (see the worked examples in the sidebar).

Web of Science vs. Scopus and OpenAlex

Web of Science is one of several competing citation databases researchers, librarians, and research offices use for literature discovery and bibliometric analysis — most often compared against Elsevier’s Scopus and the open, non-proprietary OpenAlex. The three differ in ownership, journal-selection criteria, coverage, and the citation metrics each one calculates (Web of Science underlies the Journal Impact Factor via Journal Citation Reports; Scopus underlies CiteScore). For a detailed side-by-side comparison of coverage, cost, and metrics, see Scopus vs Web of Science vs OpenAlex: Comparing Bibliographic Databases.

Use in your systems

JATS XML <role> element

xml

<role vocab="credit"
      vocab-identifier="https://casrai.org/dictionary/"
      vocab-term="Web of Science"
      vocab-term-identifier="https://casrai.org/dictionary/term/web-of-science" />

Schema.org DefinedTerm (JSON-LD)

json

{
  "@context": "https://schema.org",
  "@type": "DefinedTerm",
  "@id": "https://casrai.org/dictionary/term/web-of-science",
  "name": "Web of Science",
  "identifier": "https://casrai.org/dictionary/term/web-of-science",
  "description": "Web of Science is Clarivate’s citation-indexing and research-discovery platform, not a single index in its own right. A publication counts as covered by Web of Science only once it has been evaluated and accepted into at least one of the platform’s underlying citation indices — most often the Science Citation Index Expanded, Social Sciences Citation Index, or Arts & Humanities Citation Index within the Web of Science Core Collection, or one of the platform’s regional indices — each governed by its own independent Clarivate selection criteria; being published, or indexed elsewhere such as in Scopus, does not automatically make a title searchable on Web of Science.",
  "inDefinedTermSet": "https://casrai.org/dictionary/domain/research-info-systems#set",
  "url": "https://casrai.org/dictionary/term/web-of-science",
  "sameAs": [
    "Web of Knowledge",
    "ISI Web of Knowledge",
    "Thomson Reuters Web of Knowledge",
    "WoS"
  ],
  "license": "https://creativecommons.org/licenses/by/4.0/",
  "publisher": {
    "@id": "https://casrai.org/#organization"
  },
  "dateModified": "2026-07-17T05:30:01",
  "inLanguage": "en"
}