WikiTrust is a reputation system for Wikipedia authors and content. WikiTrust computes three main quantities: edit quality, author reputation, and content reputation. The edit quality measures how well each edit, that is, each change introduced in a revision, is preserved in subsequent revisions. Authors who perform good quality edits gain reputation, and text which is revised by several high-reputation authors gains reputation. Since vandalism on the Wikipedia is usually performed by anonymous or new users (not least because long-time vandals end up banned), and is usually reverted in a reasonably short span of time, edit quality, author reputation, and content reputation are obvious candidates as features to identify vandalism on the Wikipedia. Indeed, using the full set of features computed by WikiTrust, we have been able to construct classifiers that identify vandalism with a recall of 83.5%, a precision of 48.5%, and a false positive rate of 8%, for an area under the ROC curve of 93.4%. If we limit ourselves to the set of features available at the time an edit is made (when the edit quality is still unknown), the classifier achieves a recall of 77.1%, a precision of 36.9%, and a false positive rate of 12.2%, for an area under the ROC curve of 90.4%. Using these classifiers, we have implemented a simple Web API that provides the vandalism estimate for every revision of the English Wikipedia. The API can be used both to identify vandalism that needs to be reverted, and to select highquality, non-vandalized recent revisions of any given Wikipedia article. These recent high-quality revisions can be included in static snapshots of the Wikipedia, or they can be used whenever tolerance to vandalism is low (as in a school setting, or whenever the material is widely disseminated).