CLEF-2026 CheckThat! Lab -- 2nd Call for Participation

(apologies for cross-posting)

Dear colleague,

We invite you to participate in the 2026 edition of the CheckThat! Lab at CLEF 2026. This year, we feature three tasks ---two follow-up and one new--- that correspond to important components within and around the full fact-checking pipeline in multiple languages:

Task 1 Source Retrieval for Scientific Web Claims: Given a social media post that contains a scientific claim and an implicit reference to a scientific paper (mentions it without a URL), retrieve the mentioned paper from a pool of candidate papers. Available in English, German, and French.

Task 2 Fact-Checking Numerical Claims: Given claims, potential evidences, and possible reasoning paths, rank the reasoning paths and provide an output of verdict. Available in Arabic, English, and Spanish.

Task 3 Generating Full Fact-Checking Articles: Given a claim, its veracity, and a set of evidence documents consulted for fact-checking the claim, generate a full fact-checking article.

Register and participate: https://clef-labs-registration.dipintra.it/
Further information: https://checkthat.gitlab.io/
Datasets: https://gitlab.com/checkthat_lab/clef2026-checkthat-lab (training materials released)
Discord Server: https://discord.gg/PEMh4a2YHV

Important Dates
---------------------
- November 2025: Lab registration opened
- December 2025: sample materials released
- December - February 2026: training materials released
- 23 April 2026: Lab registration closes
- 24 April 2026: Beginning of the evaluation cycle (test sets release)
- 7 May 2026 (23:59 AOE): End of the evaluation cycle (run submission)
- 28 May 2026: Deadline for the submission of working notes [CEUR-WS]
- 29 May - 27 June 2026: Review process of participant papers
- 30 June 2026: Notification of Acceptance for working notes [CEUR-WS]
- 6 July 2026: Camera Ready Copy of working note papers [CEUR-WS]
- 10 July 2026: Regular Conference Registration Ends
- 31 August 2026: Late Conference Registration Ends
- 21-24 September 2026: CLEF 2026 Conference in Jena, Germany

Best regards,
The CLEF-2026 CheckThat! Lab Shared Task Organizers




Dr. Dimitar Dimitrov

Head of team Information Extraction & Linking

KTS / Information Extraction & Linking


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+49 (0) 221 47694 512

dimitar.dimitrov@gesis.org<mailto:dimitar.dimitrov@gesis.org>



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