The QCD axion is much of an an unavoidable consequence of the Peccei-Quinn mechanism to suppress CP violation in the strong interactions below the experimental limits. What is more, it turns out to be also an unavoidable dark matter candidate.
After briefly reviewing the theoretical motivation for the QCD axion, we will devise the panorama of the experimental searches that have been proposed to search for the QCD axion experimentally in a direct (in purely laboratory experiments) and indirect way and the current experimental efforts.