Trainline

Trainline lets travellers search, compare and buy train and bus tickets from more than 200 operators across the UK and Europe, covering routes such as London to Paris, Paris to Amsterdam and Barcelona to Madrid, national rail networks including South Western Railway, Caledonian Sleeper, Thameslink and Southeastern, and operators such as Eurostar, Trenitalia, Deutsche Bahn, SNCF, Renfe and OBB, alongside a Eurail Pass, a national rail map and travel guides covering topics such as the difference between Standard and First Class and how to travel Spain by train.

Its ads.txt file lists 52 ad systems, with 15 sold directly and 46 through resellers.