The performance of the ATLAS Inner Detector tracking trigger in high pileup collisions at 13 TeV at the Large Hadron Collider (Run 2) and plans for Run 3

The performance of the Inner Detector tracking trigger of the ATLAS experiment at the LHC is evaluated for the data-taking period of Run 2 (2015-2018). The Inner Detector tracking was used for the muon, electron, tau and b-jet triggers, and its high performance is essential for the ATLAS physics programme, including many precision measurements of the Standard Model and searches for new physics. The detailed efficiencies and resolutions of the trigger for a wide range of physics signatures are presented for the Run 2 data. In preparation for LHC Run 3, which started in the summer of 2022, the application of Inner Detector tracking in the trigger has been significantly expanded, in particular, full-detector tracking is now utilized for hadronic signatures such as jets and missing transverse energy triggers for the first time. To meet computing resource limitations various improvements, including machine-learning-based track seeding, have been developed.