The CLEF Conference addresses all aspects of Information Access in any modality and language. The CLEF conference includes presentation of research papers and a series of workshops presenting the results of lab-based comparative evaluation benchmarks. CLEF 2021 in Bucharest is the 12th year of the CLEF Conference series and the 22nd year of the CLEF initiative as a forum for information retrieval (IR) evaluation. The CLEF conference has a clear focus on experimental IR as carried out within evaluation forums (e.g., CLEF Labs, TREC, NTCIR, FIRE, MediaEval, RomIP, SemEval, and TAC) with special attention to the challenges of multimodality, multilinguality, and interactive search also considering specific classes of users as children, students, impaired users in different tasks (e.g., academic, professional, or everyday-life).

We invite paper submissions on significant new insights demonstrated on IR test collections, on analysis of IR test collections and evaluation measures, as well as on concrete proposals to push the boundaries of the Cranfield style evaluation paradigm.

All submissions to the CLEF main conference will be reviewed on the basis of relevance, originality, importance, and clarity. CLEF welcomes papers that describe rigorous hypothesis testing regardless of whether the results are positive or negative. CLEF also welcomes past runs/results/data analysis and new data collections. Methods are expected to be written so that they are reproducible by others, and the logic of the research design is clearly described in the paper. The conference proceedings will be published in the Springer Lecture Notes in Computer Science (LNCS).