We report a universal detergent-free method, named Sample Preparation by Easy Extraction and Digestion (SPEED), which consists of three mandatory steps, acidification, neutralization and digestion. SPEED is a universal method for peptide generation from various sources and is easily applicable even for lysis-resistant sample types. The protocol is highly reproducible, virtually loss-less and enables very rapid sample processing. SPEED is superior to detergent/chaotropic agent-based methods for quantitative proteomics and enhances proteome coverage for challenging samples.