Systems and methods perform asynchronous error checking on a structured document. In accordance with the systems/methods, a first thread, such as a main application thread of a document editor, parses the document to identify one or more new elements included therein and create copies of the one or more new elements. A second thread, such as a background thread, applies error checking to the copies of the one or more new elements to generate error results corresponding to the one or more new elements. The first thread the uses the error results to indicate errors in association with the one or more new elements.