Silicon nanowires are of proven importance in such diverse fields as energy production and storage, flexible electronics, and biomedicine due to the unique characteristics that emerge from their 1D semiconducting nature and their mechanical properties. Here, the synthesis of biodegradable porous silicon barcode nanowires by metal-assisted electroless etching of single-crystal silicon with resistivities ranging from 0.0008 to 10 Omega cm is reported. The geometry of the barcode nanowires is defined by nanolithography and their multicolor reflectance and photoluminescence is characterized. Phase diagrams are developed for the different nanostructures obtained as a function of metal catalyst, H2O2 concentration, ethanol concentration, and silicon resistivity, and a mechanism that explains these observations is proposed. These nanowires are biodegradable, and their degradation time can be modulated by surface treatments.