Updated project metadata. Studies have revealed dozens of functional peptides in putative ‘noncoding’ regions and raised the question of how many proteins are encoded by noncanonical open reading frames (ORFs). We comprehensively annotated genome-wide translated ORFs across five eukaryotic by analyzing ribosome profiling reads. We revealed pervasive translation in annotated untranslated regions of mRNAs or off-frame regions (i.e., uORFs, dORFs, and iORFs). We developed a logistic regression model based on ORF features to calculate the peptide functional probability in humans. Systematic ectopic expression experiments showed that peptides encoded by ncORFs follow the basic principles governing conventional protein subcellular localization and carry out diverse biological functions.