For more than a decade, libraries have started to "collect the web". National libraries in particular select, collect and store publications and websites from their national domain, seeing this as a task similar to traditional legal deposit. The collection policies and collecting methods vary, so that it is difficult to compare the quantity and quality of the respective web archives. In order to harmonize the evaluation of web archives, ISO TC 46 SC 8 has produced a Technical Report that standardizes the terminology and statistics and offers tested indicators for assessing the quality of web archiving. The paper describes the aimsand contents of the ISO Report.