eCFR data originates with the files used to produce the print and PDF editions. During the publication process these are transformed into bulk XML files made available by the Government Publishing Office (GPO).
In order to create the point-in-time features of the eCFR we process these XML files into smaller units that we then track over time. Our APIs provide access to these various transformations and generated metadata as well as historical search.
No API keys are needed; all you need is an HTTP client or browser.