MethMarker facilitates the design of DNA methylation assays for COBRA, bisulfite SNuPE, bisulfite pyrosequencing, MethyLight and MSP. It also implements a systematic workflow for design, optimization and (computational) validation of DNA methylation biomarkers. This workflow starts from a preselected differentially methylated region (DMR) and results in an optimized DNA methylation assay that is ready to be tested in a large-scale clinical trial.