This paper presents a simple, cost effective and reliable image processing technique for deformation measurement in geotextiles during wide width tensile strength tests. Localised strains are likely to be generated in the geotextiles due to production defects, seams and punctures. Accurate measurement of localised strains will help in better understanding the failure mechanism, maintaining proper quality control and developing accurate design procedures. Previous researchers have applied image-based strain measurement techniques using a charged coupled device camera for localised strain measurements, but those methods are expensive and not widely available. In the present study, a new method is proposed based on a complementary metal-oxide semiconductor camera, which is cost effective and easily available. The technique was applied for five different types of geotextiles, considering their range of applications. Three synthetic (one woven and two nonwoven), two natural (woven and nonwoven jute) geotextiles were used. Open source MATLAB module GeoPIV-RG softwarewas used for the analysis. The methodwas found to give accurate measurements of deformation patterns within an acceptable tolerance, with the added advantages of simplicity and cost-effectiveness. An attempt was also made to determine the feasibility of using a smartphone camera for image acquisition, thereby making the image processing technique more widespread and affordable. © 2016 Thomas Telford Ltd.