This page documents our efforts to track political advertising and produce an ad transparency report for the 2019 European Parliament Election.We attempted to download a copy of the political ads on a daily basis using the Facebook Ad Library API and the Google Ad Library, starting on March 29 and May 11 respectively, when the two companies released their political ads archive. We provide this data collection log, so that external researchers, journalists, analysts, and readers may examine our methods and assess the data presented in our reports.Facebook Ad Library APIScroll down Facebook provides an Application Programmable Interface ("API") to authorized users who may search for ads in their archive. However, due to the inconsistent state of the Facebook Ad Library API, our methods to scan and discover ads must be adapted on a daily and sometimes hourly basis — to deal with design limitations, data issues, and numerous software bugs in the Facebook Ad Library API.Despite our best efforts to help Facebook debug their system, the majority of the issues were not resolved. The API delivered incomplete data on most days from its release through May 16, when Facebook fixed a critical bug. The API was broken again from May 18 through May 26, the last day of the elections.We regret we do not have reliable or predictable instructions on how to retrieve political ads from Facebook. Visit the methods page for our default crawler settings and a list of suggested workarounds for known bugs, or scroll down to see our log.In general, we encountered three categories of issues with the Facebook Ad Library API. First, software programming errors that cripple a user's ability to complete even a single search including the following bugs: