We present the R²D² redundancy detector. R²D² identifies redundant code fragments on large software systems. For each pair of code fragments, R²D² uses a combination of techniques ranging from syntax-based analysis to semantics-based analysis, that detect positive and negative evidences regarding the redundancy of the analyzed code fragments. These evidences are combined according to a well-defined model and fragments sufficiently redundant are reported to the user. R²D² explores several techniques and heuristics to operate within reasonable time and space bounds and is designed to be extensible.