Image binarization is the procedure of parting of pixel values into dual collections, black as foreground and white as background. Thresholding has found to be a well-known technique used for binarization of document images. Thresholding is further divide into the global and local thresholding technique. In document with uniform contrast delivery of background and foreground, global thresholding is has found to be best technique. In degraded documents, where extensive background noise or difference in contrast and brightness exists i.e. there exists many pixels that cannot be effortlessly categorized as foreground or background. In such cases, local thresholding has significant over available techniques. The main objective of this paper is to evaluate the different image binarization techniques to find the gaps in existing techniques.