The research has shown successful application of ionic liquids (ILs) as drilling fluid additives for modifying the mud rheology. Ionic liquids are tuneable solvents comprising of hundreds of combination of various cations and anions. The cationic portion mainly comprises of a side alkyl chain which plays an important role in altering the drilling fluid properties. This review mainly focusses on finding the impact of alkyl chain length on yield point, plastic viscosity and filtration properties of water based mud at room temperature. The paper also incorporates the X-ray diffraction (XRD) analysis carried out on various ionic liquids by different research groups which confirms how the intercalation between ionic liquid and Na-Bt (Sodium Bentonite) changes the structure of clay and thus alters the rheology of the mud. It can be concluded that ionic liquids act as rheology modifiers by intercalating between the clay layers and thus changing the d-spacing of the clay. Moreover, the hydrophobicity, polarity and solubility of alkyl chain play an important role in altering the wettability and dispersion behavior of clay which modify the filtration as well as rheological properties of the mud. © 2021, The Author(s).