We developed a nanopore tool to measure how enzymes move along nucleic acid chains. In this technique, which evolved from our effort in developing nanopore sequencing, the ion current through an engineered protein nanopore is used to measure the motion of the DNA or RNA. With its unprecedented spatiotemporal resolution this new single-molecule tool resolves sub-millisecond and sub-nucleotide-long enzyme steps while providing the exact nucleotide sequence context within the enzyme. In addition, the tool has high throughput and is relatively simple to set up. We find surprisingly strong sequence-dependence in the kinetics of many types of helicases such as in Hel308, PcrA, RecQ, or the SARS-CoV-2 helicase nsp13. Furthermore, we have recorded data with DNA- and RNA-polymerases and reverse transcriptases. With each enzyme we discover behavior that had not been observable with any other single-molecule technique.