Photometry with the transit method has arguably been the most successful exoplanet discovery method to date. A short overview about the rise of that method to its present status is given. The method's strength is the rich set of parameters that can be obtained from transiting planets, in particular in combination with radial velocity observations; the basic principles of these parameters are given, with explicit formulations for the transit detection probability and the times of transit epochs in comparison to radial velocity epochs. The transit method has however also drawbacks, which are the low probability of properly aligned planet systems and the presence of astrophysical phenomena that may mimic transits and give rise to false detection positives. In the second part, we outline the main factors that determine the design of transit surveys, such as the size of the survey sample, the temporal coverage, the photometric precision, the sample brightness and the methods to extract transit events from observed light curves. Lastly, an overview over past, current, and future transit surveys is given. For these surveys we indicate their basic instrument configuration and their planet catch, including the ranges of planet sizes and stellar magnitudes that were encountered. Current and future transit detection experiments concentrate primarily on bright or special targets, and we expect that the transit method remains a principal driver of exoplanet science, through new discoveries to be made and through the development of new generations of instruments.

To be published in: Handbook of Exoplanets, 2nd Edition, Hans Deeg and Juan Antonio Belmonte (Eds. in Chief), Springer International Publishing AG, part of Springer Nature. This is a substantial update over the chapter published in the first edition of the Handbook in 2018