How best to measure molecular diffusion in a mixture is a topic that has been studied widely and is an essential element of various scientific disciplines. In the oil and gas industry, accurate acid diffusion measurement is vital to the design of acid treatments. In fact, predictions of acid penetration distance in hydraulic fractures and wormhole length during matrix acidization are not possible without accurate diffusion coefficient data or correlations. The present study explains and critically compares the various methods used to measure the acid diffusion coefficient, including the rotating disk apparatuses, core flooding, nuclear magnetic resonance, annular reactors, parallel plates, and diffusion cells. This study also summarizes the impacts of acid type, chemical additives, minerals, temperature, and pressure on diffusion measurement. Tabulated summaries of the diffusion coefficient values associated with various acid types are also provided. Popular correlations for predicting the acid diffusion coefficient are also thoroughly discussed. Finally, recommendations are provided regarding best practices for obtaining accurate acid diffusion measurement data.