This research proposal aims to investigate the local structure of high-entropy alloy (HEA) REBa2Cu3O7−δ (RE123) thin films, where RE represents rare earth elements such as Y, Sm, Eu, Dy, and Ho. RE123 compounds are some of the most studied high-temperature superconductors (HTS) with applications in high magnetic field environments like magnetic resonance imaging (MRI), energy storage, and fusion reactors. The introduction of the high-entropy alloying concept to these superconducting systems introduces configurational disorder by incorporating multiple RE elements at near-equal concentrations. HEA systems are known to enhance material stability under extreme conditions, making them promising for next-generation superconducting applications. In particular, recent studies have shown that HEA RE123 thin films exhibit stable superconducting properties even under high magnetic fields, but the effects of reduced dimensionality and high-entropy alloying on the local structure remain unexplored.This study proposes to examine the local lattice structure of these thin films through temperature-dependent extended x-ray absorption fine structure (EXAFS) measurements at the Cu K-edge. By analysing the Cu-O bond lengths and local distortions across a temperature range of 20 K to 300 K, the proposed research aims to correlate these structural changes with superconducting properties such as Tc and Jc. Four samples with varying RE compositions will be investigated, including a pure YBa2Cu3O7−δ system and HEA films with increasing RE substitution. The findings are expected to clarify how high-entropy alloying and reduced dimensionality impact the local environment of CuO₂ planes and contribute to the superconducting performance of RE123 thin films under extreme conditions. The study will provide insights into the design of advanced superconducting materials for technological applications in extreme environments.