Content management
Since 2011, the non-profit Hypothes Is Project has offered the free, open web annotation service [[Hypothes.is]]. The service features annotation via a Chrome extension, bookmarklet or proxy server, as well as integration into a [[Learning management system|LMS]] or [[Content management system|CMS]]. Both [[Web annotation|webpages]] and [[Portable Document Format#Annotation|PDFs]] can be annotated. Other web-based text annotation systems are collaborative software for distributed text editing and versioning, which also feature annotation and commenting interfaces.