---
type: Glossary Term
title: "Well-known URI"
description: "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."
resource: "https://agenticweb.wiki/terms/well-known/"
tags: ["glossary", "discover"]
status: stable
generated: { by: agenticweb-builder/1.0, at: 2026-10-30T00:00:00Z }
verified: { by: process:agenticweb-engine, at: 2026-10-30T00:00:00Z }
stale_after: 2026-11-29T00:00:00Z
sources:
  - id: ref-1
    resource: "https://www.rfc-editor.org/rfc/rfc8615"
    last_modified: 2019-05-01T00:00:00Z
---

# Well-known URI

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.

# Knowledge Graph

* **Related standards**: [Agent2Agent Protocol (A2A)](/okf/protocols/a2a.md), [Agentic Resource Discovery (ARD)](/okf/protocols/ard.md), [AI Catalog well-known file](/okf/protocols/ai-catalog-well-known-file.md)

[^ref-1]: https://www.rfc-editor.org/rfc/rfc8615 (https://www.rfc-editor.org/rfc/rfc8615)