The Short Answer

SCI, SCIE, and ESCI are all part of the Web of Science Core Collection, maintained by Clarivate. They are not competing databases — they're different tiers within the same system. Here's the practical distinction:

  • SCI (Science Citation Index) — the original, older index. Clarivate merged it into SCIE in January 2020, so "SCI" is largely a legacy term today. Many researchers and institutions still say "SCI journal" out of habit, but there is no longer a separate, actively maintained SCI database distinct from SCIE.
  • SCIE (Science Citation Index Expanded) — the current, active index covering natural and applied sciences. As of 2026 it covers roughly 9,500 journals across around 178 subject categories. When people today say "SCI-indexed," they almost always mean SCIE.
  • ESCI (Emerging Sources Citation Index) — a separate, quality-controlled entry tier launched in 2015 for journals that meet Web of Science's editorial standards but haven't yet built the citation history required for SCIE. As of 2026, ESCI covers approximately 8,000 journals.

What Changed When SCI and SCIE Merged

In January 2020, Clarivate officially merged the Science Citation Index (SCI) into the Science Citation Index Expanded (SCIE). Before the merger, SCI was a smaller, print-era index and SCIE was its larger, expanded online counterpart. After the merger, there is effectively one science index — SCIE — and the "SCI" label persists mainly in academic conversation, CVs, and some older institutional policies that haven't updated their terminology.

This matters practically: if a university, funding body, or promotion committee still asks for "SCI publications," it's worth clarifying with them whether they mean SCIE specifically, since that's the index that actually exists today.

Where ESCI Fits — and Why It's Not "Lesser" in the Way Many Assume

ESCI is sometimes described informally as a "waiting room" for SCIE, and there's some truth to that — journals can be promoted from ESCI into SCIE once they build sufficient citation impact. But ESCI is not simply an unranked or low-quality tier. ESCI journals:

  • Undergo the same core editorial evaluation as other Web of Science indexes (peer review standards, publishing ethics, timeliness)
  • Are fully indexed and searchable within Web of Science, with citations tracked
  • Have received an official Journal Impact Factor since the JCR 2022 edition (released June 2023) — a common misconception is that ESCI journals have no Impact Factor, which was true before 2022 but is now outdated

What ESCI journals have not yet demonstrated is the sustained, broad citation impact Clarivate requires for promotion into SCIE. Institutions vary in how they weigh ESCI versus SCIE for evaluation purposes — some treat them equivalently, others give SCIE more weight — so it's worth checking your specific institution's policy rather than assuming.

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Quick Comparison: SCI vs SCIE vs ESCI

SCI — legacy term; merged into SCIE by Clarivate in January 2020; no longer a separate active index.

SCIE — the current, active science index; ~9,500 journals; established citation impact required.

ESCI — entry-tier index since 2015; ~8,000 journals; has carried an official Impact Factor since JCR 2022.

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SCI SCIE ESCI journal index comparison and publication support

A Note on Web of Science vs Scopus

Different Systems, Different Rules

SCI, SCIE, and ESCI all belong to Clarivate's Web of Science Core Collection — a separate system from Scopus, which is maintained by Elsevier. A journal may be indexed in Scopus, Web of Science, both, or neither. Being covered by one does not guarantee coverage by the other, and the two use different evaluation criteria.

Always Verify Directly Before Submission

Because indexing status can change — journals are added, promoted between tiers, or occasionally delisted — always confirm a journal's current status directly through the official Clarivate Master Journal List (for SCIE/ESCI) or the Scopus Sources database (for Scopus), rather than relying on older articles, third-party lists, or a journal's own website claims. For the full Scopus-specific walkthrough, see our Scopus verification guide.

Researchers in Türkiye should also see our guide on YÖK's 2026 national Scopus evaluation requirement. Ready to find journals that fit your research? Get journal selection support.

Frequently Asked Questions About SCI, SCIE, and ESCI

Effectively, yes, as of today. Clarivate merged the Science Citation Index (SCI) into the Science Citation Index Expanded (SCIE) in January 2020. "SCI" is now largely a legacy term used in academic conversation; the index that actually exists and is actively maintained is SCIE.

Yes, since the JCR 2022 edition, released in June 2023. Before that, ESCI journals did not receive a Journal Impact Factor even though their citations were tracked. This is a common point of outdated information — many articles online still describe ESCI as having no Impact Factor.

Yes. Clarivate can promote a journal from ESCI to SCIE once it demonstrates sufficient citation impact over time. Promotion is not automatic or guaranteed, and Clarivate does not always backfill earlier issues into SCIE when a journal is promoted — so a specific paper published before the promotion may remain indexed under ESCI even after the journal moves to SCIE.

Not always. Some universities and funding bodies count ESCI and SCIE publications equally; others weigh SCIE more heavily in evaluation, promotion, or grant criteria. Because policies vary by institution and country, it's worth checking your specific institution's current requirements rather than assuming.

No. SCIE is part of Clarivate's Web of Science Core Collection; Scopus is a separate database maintained by Elsevier. A journal can be indexed in one, both, or neither, and coverage should be verified independently for each database before submission.

Search the exact journal title in Clarivate's official Master Journal List, which shows current Web of Science coverage and which index a journal belongs to. Because status can change, verify again close to your actual submission date rather than relying on an older check.