---
title: "Authentication"
description: "Proxy uses OAuth 2.0 with PKCE and dynamic client registration per the MCP authorization spec. No API keys."
---

## Overview

There are no API keys to create or paste. Proxy is an OAuth 2.0 protected resource, and MCP clients discover and complete the flow on their own.

| Step | What happens |
| --- | --- |
| 1 | Client sends a request to `/mcp` without a token and receives **401** |
| 2 | The `WWW-Authenticate` header names the protected resource metadata URL |
| 3 | Client reads the metadata, finds the authorization server, and registers itself (dynamic client registration) |
| 4 | Client opens the browser for sign-in with PKCE |
| 5 | Client retries with a bearer token; tools now work |

## Discovery endpoints

| Document | URL |
| --- | --- |
| Protected resource metadata (RFC 9728) | `https://mcp.useproxy.dev/.well-known/oauth-protected-resource/mcp` |
| Authorization server metadata (RFC 8414) | `https://mcp.useproxy.dev/.well-known/oauth-authorization-server` |
| Resource identifier | `https://mcp.useproxy.dev/mcp` |

## The 401 handshake

An unauthenticated `initialize` is expected to fail. This is the spec, not an outage:

```http
HTTP/1.1 401 Unauthorized
WWW-Authenticate: Bearer error="invalid_token",
  resource_metadata="https://mcp.useproxy.dev/.well-known/oauth-protected-resource/mcp"
```

A compliant client follows `resource_metadata` and completes OAuth before retrying. Clients that never read that header cannot connect to any spec-compliant MCP server.

## Redirect URIs

Dynamic client registration is open. A registration is accepted with any redirect URI, but `authorize` only completes for URIs that match an allowed pattern for known clients (Claude, ChatGPT, Cursor, Codex, Copilot, Zed, MCP Inspector, localhost). If your client is rejected at authorize time, contact [support@useproxy.dev](mailto:support@useproxy.dev) with the redirect URI.

## Personal tokens

The [CLI installer](/docs/clients#cli-installer-any-client) runs the browser flow once and issues a long-lived personal bearer token (prefix `proxy_`). Send it as `Authorization: Bearer <token>` on `/mcp`. Use it for clients that cannot open a browser or for scripted agents.

:::note
Personal tokens are scoped to one account and do not expire. Re-running the installer replaces the previous token; there is no self-serve revoke yet, so email support to kill a leaked token.
:::

## Reference

The agent-facing version of this page, in plain markdown, is at [/auth.md](https://useproxy.dev/auth.md).