Digital Humanities (DH) is a newer scientific discipline characterized by interdisciplinary collaboration and innovative use and / or study of digital technology within humanistic research. DH sees present period as an opportunity for the renewal of humanities, trying to point out new contributions and ways of creating knowledge, enabled by a networked digital environment. One of these ways is crowdsourcing, the concept of cooperation with the public in the Web 2.0 environment, taken from the business world and successfully adapted to the application of libraries and other heritage institutions projects. The aim of this paper is to present the theoretical framework of digital humanities and the role of libraries in DH and crowdsourcing, and to explore examples of crowdsourcing projects applied in the cultural-heritage sector, ie in libraries. The paper describes the classification of the crowdsourcing initiatives in digital humanities, ie in the heritage institutions, with the analysis of projects that included OCR correction, gamification, text transcription, TEI marking, social tagging, co-creation of content, and georeferencing. The very successful results of these projects indicate the justification of the trust in the users and the usefulness of their contribution in creating and improving the collections, contents and services of the heritage institutions, that is, they point to the importance of the real and potential benefits of crowdsourcing projects both for users and heritage institutions, with emphasis on libraries. Among other things, crowdsourcing projects have contributed to improved search and use of digital library collections, affecting significantly the reduction of the time and financial costs required for subsequent processing of data in digitized documents. Along with quality digital tools and interesting content, as an important factor in the success of crowdsourcing projects in this sector, special emphasis was placed on the motivation of super volunteers.