This is the repository of the data quality control (QC) software for the ALICE O2 system. QuickStart Requirements Setup Execution Basic workflow Readout chain Modules development Context QC architecture DPL Data Sampling Bypassing the Data Sampling Code Organization User-defined modules Module creation Test run Modification of a Task Addition of a Check Commit Code DPL workflow customization Plugging Data Sampling and QC into an existing DPL workflow Advanced topics Data Inspector Use MySQL as QC backend Local CCDB setup Local QCG (QC GUI) setup Information Service Configuration files details Frequently Asked Questions