Frequently asked questions

What is the CFR?

The Code of Federal Regulations is the official rulebook of the US federal government. When Congress passes a law, agencies write the detailed rules that put it into practice — what a food label must say, how much of a pollutant a plant may emit, how a pension must be reported. Those rules, collected and organised into 50 subject-matter titles, are the CFR. It is the day-to-day law that businesses and agencies actually operate under.

What is the eCFR, and how is it different?

The eCFR is the government's continuously updated online edition of the CFR — new rule changes appear within days. The printed CFR is republished only once a year, so the eCFR is what anyone who needs current rules actually reads. This site measures the eCFR.

Is this site an official government source?

No. eCFR Atlas is an independent, open-source project with no government affiliation. Every page links back to the official text on the eCFR, and every number here is this project's own measurement. For legal purposes, only the annual printed CFR and the Federal Register are authoritative — details on the about page.

How current is the data?

The current build reflects the eCFR as of September 30, 2026. The site re-measures the eCFR every weekday, and every page footer carries the exact date its data reflects. A change the government published yesterday is typically measured here within a business day.

Why measure regulation in words?

Words are a blunt instrument — but an honest one. Counting pages depends on formatting; counting “rules” depends on what you call a rule; words can be measured the same way for every agency and compared over time. A word count will not tell you whether a rule is wise, but it tells you where the bulk of the rulebook sits, which is where research starts.

Why do agencies show two different numbers?

Because some rules have more than one agency in charge. An agency's total regulation counts every rule it manages in full — shared or not — which is the right way to state its responsibility. Its share of all regulation splits jointly managed rules evenly between their agencies, which is the right way to compare or add agencies without counting any rule twice. When an agency shares nothing, the two numbers are identical. The glossary has the full definitions.

Why do some values say “Not measured”?

When something could not be measured — a fetch failed, a document would not parse — this site says so instead of guessing. A dash with a reason can be investigated; a silently wrong number cannot. The data quality page lists every unmeasured value in the current build, with its reason.

How exactly are words counted?

By parsing the eCFR's official XML and counting the words of regulation text, with headings, authority notes, source citations and tables of contents excluded. Nothing is estimated from file sizes or extrapolated. The precise rules — written to be disagreed with — are on the methodology page.

Can I use this data?

Yes. The project is open source, and everything on the site is available as JSON from the public API under the same measurement rules — anonymous access works immediately, and a free key raises the rate limit.