# Ecfr (ecfr.io)

Lets users search and read current and dated editions of US federal regulations, with a JSON interface for programmatic and AI agent access.

- Atlas card: https://inite.ai/en/atlas/ecfr.io
- Site: https://ecfr.io
- For: Developers and AI agents who need free, programmatic read-only access to US federal regulations
- Use not measured/100 · alive 100/100

## Used for

- search federal regulations through the free JSON API
- browse current titles of the Code of Federal Regulations
- open dated historical annual CFR editions for comparison

## Price

Not read yet.

## For developers

- OpenAPI: https://ecfr.io/openapi.json (3 paths)
- API docs: https://ecfr.io/developers
- MCP server: io.ecfr/ecfr (namespace; open on 2026-10-15, 3 tools)
- MCP server: io.ecfr/uscode (namespace; open on 2026-10-15, 3 tools)
- Read 2026-10-15

## Your data

- Certifications stated: none
- Read 2026-10-15

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Source: INITE Atlas, https://inite.ai/en/atlas/ecfr.io. JSON: https://inite.ai/api/atlas/ecfr.io. MCP: https://inite.ai/api/mcp (atlas_lookup).