As explained in Section 4.1 of Roland Schäfer (2015) Processing and querying large web corpora with the COW14 architecture, we have to take certain measures in order to stay within the bounds of German copyright laws. This means that we only release sentence shuffles, i.e., corpora which are just bags of sentences. In other words, there are no documents in released versions of COW corpora, just single sentences without contexts. The original URL plus some other meta data are recorded for each sentence, however.
Starting 2017, COW uses NoSketchEngine exclusively. Please find the interface at https://www.webcorpora.org/.