This paper presents a new Web-based annotation tool, the “CLARIN-EL Web-based Annotation Tool”. Based on an existing annotation infrastructure offered by the “Ellogon” language enginneering platform, this new tool transfers a large part of Ellogon’s features and functionalities to a Web environment, by exploiting the capabilities of cloud computing. This new annotation tool is able to support a wide range of annotation tasks, through user provided annotation schemas in XML. The new annotation tool has already been employed in several annotation tasks, including the anotation of arguments, which is presented as a use case. The CLARIN-EL annotation tool is compared to existing solutions along several dimensions and features. Finally, future work includes the improvement of integration with the CLARIN-EL infrastructure, and the inclusion of features not currently supported, such as the annotation of aligned documents.