Examples
Worked examples
- Is an instance
A biology journal that passes Clarivate's editorial and impact review is added to the Science Citation Index Expanded, and its articles' cited references become part of the Web of Science citation graph.
- Is an instance
A university library cites a journal's SCIE-indexed status, alongside its Journal Impact Factor from the same Web of Science Core Collection data, in a subscription renewal review.
Counter-examples
Looks similar, but isn't
- Not an instance
A journal listed only in Scopus, with no separate Web of Science evaluation, is not automatically SCIE-indexed — the two databases have independent selection processes.
- Not an instance
A conference paper indexed only in the Conference Proceedings Citation Index is not the same as being indexed in SCIE, even though both sit within the same Web of Science Core Collection.
Editorial commentary
The Science Citation Index (SCI) is a multidisciplinary citation index — a database that records not just what a scientific paper says, but every reference it cites, so a researcher can trace forward and backward through the literature by citation link rather than by keyword alone. Its expanded, currently maintained edition, the Science Citation Index Expanded (SCIE), is one of the citation indexes that make up Clarivate’s Web of Science Core Collection. “SCI” and “Web of Science” are related but not interchangeable: SCI/SCIE is one specific index within the Web of Science Core Collection, not the platform itself (see Distinguishing SCI from Web of Science and Scopus, below).
History: Eugene Garfield, ISI, and the origin of citation indexing
Citation indexing was proposed by information scientist Eugene Garfield in 1955 as a way to link scholarly literature by the citations authors themselves draw between papers, rather than by subject classification alone. Garfield founded the Institute for Scientific Information (ISI) in Philadelphia in 1960, and ISI published the first Science Citation Index in 1964 — widely regarded as the world’s first citation index.
ISI extended the same citation-indexing model into other domains: the Social Sciences Citation Index (SSCI) launched in 1973 and the Arts & Humanities Citation Index (AHCI) in 1978. ISI also introduced the Journal Citation Reports (JCR) in 1976, which popularized the Journal Impact Factor (JIF) as a journal-level metric derived from the underlying citation data (see CASRAI’s Journal Impact Factor (JIF) entry for how that metric is calculated and why it is widely misapplied to individual researchers).
Corporate history: ISI to Thomson Reuters to Clarivate
The Science Citation Index has changed corporate ownership several times since Garfield founded ISI, and older references to “ISI” or “Thomson Reuters” as the current owner are out of date:
- 1992 — The Thomson Corporation acquired ISI.
- 2008 — Thomson merged with Reuters to form Thomson Reuters, and the index was marketed for a period as “Thomson Reuters Web of Science.”
- 2016 — Thomson Reuters’ scientific and academic research division, including ISI and the Web of Science business, was spun out and sold, and rebranded as Clarivate (initially Clarivate Analytics).
As of 2026, the Science Citation Index Expanded is maintained by Clarivate as part of the Web of Science Core Collection, and ISI continues to operate as Clarivate’s research arm, carrying forward journal-evaluation and citation-indexing work descended directly from Garfield’s original methodology. Any current statement about who “owns” SCI/SCIE should cite Clarivate, not ISI or Thomson Reuters as standalone owners.
What SCIE covers today
Per Clarivate’s own current description of the product, the Science Citation Index Expanded indexes several thousand actively publishing journals across roughly 178 science subject categories, with backfile coverage extending to 1900 and tens of millions of indexed records. Coverage figures change as journals are added, delisted, or discontinued, so a researcher checking current numbers should consult Clarivate’s Master Journal List directly rather than treat any fixed figure as permanent.
Journal inclusion in SCIE is not automatic. Clarivate applies an editorial evaluation covering publishing standards (peer review, editorial rigor, ethical publishing practices, timeliness) and impact criteria (citation influence within a field) before a journal is accepted, and journals can be delisted for quality or integrity concerns after inclusion. This selectivity is precisely why SCIE indexing functions as a prestige signal in the first place — see the next section.
Distinguishing SCI/SCIE from the Web of Science platform, and from Scopus
Three distinct things are routinely conflated in casual usage:
- Science Citation Index Expanded (SCIE) is one citation index, scoped to the sciences, covering roughly 178 categories.
- Web of Science Core Collection is the umbrella product that bundles SCIE together with several sibling indexes — the Social Sciences Citation Index (SSCI), the Arts & Humanities Citation Index (AHCI), the Emerging Sources Citation Index (ESCI, for journals under evaluation that have not yet met full SCIE/SSCI/AHCI criteria), the Conference Proceedings Citation Index, and the Book Citation Index.
- Web of Science (unqualified) is Clarivate’s broader discovery platform, which layers the Core Collection together with regional and specialty databases and search/analysis tools.
Scopus, maintained by Elsevier, is a separate, competing abstract-and-citation database with its own journal-selection process and its own journal-level metric (CiteScore, the Scopus counterpart to the Journal Impact Factor — see CASRAI’s CiteScore entry). SCIE and Scopus overlap substantially in coverage but are not identical, and a journal can be indexed in one without being indexed in the other. For a structured feature-by-feature comparison, see CASRAI’s Scopus vs Web of Science vs OpenAlex comparison.
Why SCI/SCIE indexing matters to researchers and research administrators
Being indexed in the Science Citation Index Expanded (or the analogous SSCI/AHCI, depending on discipline) is widely treated as a de facto quality signal because of the editorial selectivity described above. In practice, this shows up in research administration in several concrete ways:
- Journal prestige signaling. Many institutions, national research-evaluation exercises, and some funders use SCIE/Web of Science indexing status as a filter for which publications “count” in tenure, promotion, or grant-reporting contexts — sometimes formally, sometimes informally.
- Citation tracking and bibliometrics. SCIE’s cited-reference data underlies citation counts, the Journal Impact Factor, and h-index-style researcher metrics computed on the Web of Science platform.
- Author disambiguation and CRIS integration. Web of Science records can be linked to ORCID iDs and ingested into current research information systems (CRIS), letting institutions track faculty output against a controlled, editorially-vetted source rather than an uncurated web search.
Research administrators should be cautious about treating SCIE indexing, or any single citation database’s coverage, as a complete or sufficient measure of research quality. The Declaration on Research Assessment (DORA) and the Leiden Manifesto both caution against using journal-level indicators — including index membership and the Journal Impact Factor it enables — as a proxy for the quality of an individual article or researcher.
Frequently asked questions
Is Science Citation Index the same thing as Web of Science?
No. SCI/SCIE is one citation index within Clarivate’s Web of Science Core Collection, which also includes the Social Sciences Citation Index, Arts & Humanities Citation Index, Emerging Sources Citation Index, Conference Proceedings Citation Index, and Book Citation Index. “Web of Science” more broadly refers to Clarivate’s overall discovery platform.
Who owns the Science Citation Index today?
Clarivate. The index originated with Eugene Garfield’s Institute for Scientific Information (ISI) in 1964, was acquired by the Thomson Corporation in 1992, became part of Thomson Reuters after its 2008 merger with Reuters, and was spun out and rebranded as Clarivate in 2016.
What is the difference between SCI and SCIE?
“SCI” (Science Citation Index) is the original print/early-electronic index; “SCIE” (Science Citation Index Expanded) is its current, larger electronic edition and the version actually maintained and updated today. In current usage the two terms are frequently used interchangeably to refer to the modern index, but SCIE is the technically accurate name for what is indexed and searched now.
Is Science Citation Index the same as Scopus?
No. SCIE is Clarivate’s index; Scopus is Elsevier’s separate, competing abstract-and-citation database. They use different journal-selection criteria and different journal-level metrics (Journal Impact Factor for Web of Science vs. CiteScore for Scopus), and their journal coverage overlaps but is not identical.
Does SCIE indexing guarantee a journal is high quality?
It signals that the journal passed Clarivate’s editorial and impact evaluation at the time of acceptance, which is a meaningful quality filter, but organizations such as DORA and the Leiden Manifesto caution against treating index membership, or any single journal-level indicator, as a substitute for evaluating the actual content of a specific article or researcher’s work.
References
- Clarivate, “Science Citation Index Expanded (SCIE)” product page.
- Clarivate, “The History of ISI and the work of Eugene Garfield.”
- Clarivate, “Web of Science Core Collection” product page.
- DORA, San Francisco Declaration on Research Assessment.
Machine-readable encodings
Use in your systems
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