# Well-known URI

[1 · Discover](/category/discover/)

| Well-known URI |
| --- |
| Category | [Discover](/category/discover/) |
| Also known as | .well-known, /.well-known/ |
| Related | [Agent2Agent Protocol](/protocols/a2a/), [Agentic Resource Discovery](/protocols/ard/), [AI Catalog well-known file](/protocols/ai-catalog-well-known-file/) |

[Discover](/category/discover/) A well-known URI is a path beginning /.well-known/ at the root of an origin, reserved by RFC 8615 (May 2019, obsoleting RFC 5785) so that applications needing site-wide metadata do not have to negotiate arbitrary paths or risk colliding with a site's existing URL space. Anyone minting a new well-known name is expected to register it with IANA, referencing the specification that defines its format and media type; the mechanism itself defines no content at /.well-known/ and clients should not assume anything exists there by default. The agentic web reuses this pattern heavily: /.well-known/agent-card.json (A2A), /.well-known/ard.json and its predecessor /.well-known/ai-catalog.json (ARD), and others each register or informally claim a name under this prefix rather than inventing a new discovery convention. Used by: a2a, ard, ai-catalog-well-known-file.

## Instances

Not applicable.

## See also

- [Agent2Agent Protocol](/protocols/a2a/)
- [Agentic Resource Discovery](/protocols/ard/)
- [AI Catalog well-known file](/protocols/ai-catalog-well-known-file/)

## References

- [https://www.rfc-editor.org/rfc/rfc8615](https://www.rfc-editor.org/rfc/rfc8615) (2019-05) VERIFIED

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