Federal Register Data Dictionary¶

This document describes the fields available on the Federal Register API endpoint (/api/federal_register/). For filtering, ordering, and pagination, see the Federal Register API Reference.

Overview¶

Federal Register documents are every rule, proposed rule, notice and presidential document published in the Federal Register from January 1994 to the present — about 1.01 million documents.

One row is one published document. Most fields are the Federal Register's own, served as it publishes them; Tango adds the uuid.

Authentication: Federal Register endpoints require authentication (API key or OAuth2).

Plans: every field, including full_text, is available on every plan, including Free.

Note: Federal Register documents are a flat resource with no expandable relations. The full field set is available via the shape query parameter. See Response Shaping.

Update Frequency¶

The Federal Register is read daily, and a document appears in the API the day it is picked up after publication.

The Federal Register often fills in a document's details over the few days after it is published, and those updates flow through as changes to the same row. A document published this week is more likely to change than one published last month.

Identity¶

A document is identified by its document_number and publication_date together. The document number alone is not unique: the Federal Register reused numbers across genuinely different documents, as late as 2015.

The primary key and detail-lookup value is uuid. It is derived from the document number and publication date rather than assigned sequentially, so it is stable across rebuilds of the dataset and safe to store alongside your own records.

Corrections¶

A correction is published as its own document, with its own number and row. The two directions of the link are:

• correction_of — on the correction, identifies the document it corrects.
• corrections — on the original, an array of Federal Register API URLs for the documents that correct it.

The rows are never merged, so a search for the subject of a rule can return both the rule and its corrections.

Structured fields¶

These fields are the Federal Register's own structures, returned as JSON exactly as published. On a few dozen documents they are null rather than an empty array or object.

agencies¶

An array of the agencies that issued the document, one object per agency:

A small share of agency entries (under 2%) carry only raw_name: the Federal Register printed a name it did not match to an agency record. ?fr_agency= cannot reach a document through such an entry.

These are Federal Register agency records, not Tango organizations; there is no link between the two.

{"raw_name": "Employee Benefits Security Administration", "name": "Employee Benefits Security Administration", "slug": "employee-benefits-security-administration", "id": 131, "parent_id": 271, "url": "https://www.federalregister.gov/agencies/employee-benefits-security-administration", "json_url": "https://www.federalregister.gov/api/v1/agencies/131"}

cfr_references¶

An array of the Code of Federal Regulations parts the document amends or affects:

?cfr_title= and ?cfr_part= match both spellings of part, so the filters are unaffected by the mixed type.

{"title": 14, "part": "39", "chapter": null, "citation_url": null}

dockets¶

An array of Regulations.gov dockets associated with the document:

String arrays¶

regulation_id_number_info¶

An object keyed by RIN, one entry per RIN in regulation_id_numbers. Each value is an object with title, priority_category, issue (the Unified Agenda edition, e.g. 202504), html_url and xml_url — or null when the Federal Register holds no agenda entry for that RIN.

{"2120-AA64": {"title": "Airworthiness Directives", "issue": "202504", "html_url": "https://www.federalregister.gov/regulations/2120-AA64/airworthiness-directives", "xml_url": "http://www.reginfo.gov/public/do/eAgendaViewRule?pubId=202504&RIN=2120-AA64&operation=OPERATION_EXPORT_XML"}}

regulations_dot_gov_info¶

A single object describing the document's Regulations.gov record — not keyed by RIN, despite the similar name. It is {} when Regulations.gov has no record for the document.

Keys, each present only when Regulations.gov supplies it: document_id, docket_id, agency_id, title, comments_url, comments_count, supporting_documents, supporting_documents_count, regulation_id_number, regulatory_plan (an object with title and html_url), and checked_regulationsdotgov_at.

Fields¶

Default shapes¶

• List returns: uuid, document_number, publication_date, type, subtype, title, abstract, action, agencies, cfr_references, citation, significant, comments_close_on, effective_on, html_url, pdf_url.
• Detail returns the list fields plus dates, signing_date, start_page, end_page, volume, docket_ids, dockets, regulation_id_numbers, topics, correction_of, corrections, executive_order_number, presidential_document_number, proclamation_number, comment_url, regulations_dot_gov_url, raw_text_url, body_html_url.

page_length, toc_doc, toc_subject, disposition_notes, executive_order_notes, not_received_for_publication, public_inspection_pdf_url, regulation_id_number_info and regulations_dot_gov_info are in neither default; name them in ?shape= to get them. full_text can be named on the detail endpoint only.

Usage Notes¶

• Read publication_date alongside document_number. Before 2016 a document number can belong to more than one document.
• Agencies are the Federal Register's, not Tango's. Match them with ?fr_agency= and the Federal Register slug; they do not join to Tango organizations, entities or awards.
• significant is three-valued. true, false, and null for the large majority of documents that were never designated either way.
• Alerts follow the record. federal_register is an alertable query type; a document appearing or changing fires, but a comment period closing does not. See Webhooks.

Data Sources¶

• Federal Register — every field except uuid, as published on federalregister.gov, from January 1994 forward.
• Tango — uuid.