Total Diet Study (TDS) is a cost-efficient method recommended by WHO to estimate long-term exposure to chemicals in the diet. Based on national consumption data, commonly eaten foods are selected, prepared as consumed, pooled, and analyzed for contaminants. TDS provides average contamination levels but is not suitable for detecting short-term or isolated risks. Standardized methods, supported by projects like TDS-Exposure and EFSA guidelines, enhance data quality and global comparability. This harmonized TDS includes two main sampling phases: planning and fieldwork, followed by phases of chemical analysis, of the TDS samples and subsequent exposure assessment and risk characterization. In planning, core foods are chosen using national consumption data, categorized with the FoodEx2 system, and grouped into TDS samples. Sampling considers origin, market share, season, and cooking habits. Fieldwork covers food collection, preparation according to local cooking practices, and pooling of subsamples for analysis. Chemical analysis uses validated methods (e.g., ICP-MS, GC-MS, LC-MS/MS) and should use speciation for contaminants like arsenic and mercury. Exposure assessment combines contamination and consumption data using deterministic or probabilistic models and stratifies results by demographic groups. Risk characterization compares exposure estimates with health-based guidance values (HBGVs), using tools like tolerable intakes (TDI/TWI) and the Margin of Exposure (MOE), while accounting for variability and uncertainty through sensitivity analysis and Monte Carlo simulations. Results help identify major dietary sources of contaminants and support public health decisions.