---
title: API Authentication
description: How to authenticate to the RomM REST API — session cookies, Basic, OAuth2 tokens, client tokens, and OIDC.
---

# API Authentication

RomM's REST API accepts four authentication modes. Pick the one that matches your client:

| Mode | Who it's for | How the credential is carried |
| --- | --- | --- |
| **Session cookie** | Browser UI | `Cookie: session=…` after `POST /api/auth/login` |
| **HTTP Basic** | Quick scripts, curl one-liners | `Authorization: Basic <base64(user:pass)>` |
| **OAuth2 Bearer** | Automation, CI, third-party apps | `Authorization: Bearer <jwt>` |
| **Client API Token** | Companion apps (Argosy, Grout, Playnite, custom scripts) | `Authorization: Bearer rmm_<token>` |
| **OIDC session** | Users who sign in via SSO | Same as session cookie, but issued after OIDC callback |

All of them resolve to the same scope model — see the [scope matrix in Users & Roles](../administration/users-and-roles.md#scope-matrix). A request is allowed if the active identity holds all scopes the endpoint requires.

## Base URL

```text
https://<your-instance>/api
```

When RomM is behind a reverse proxy (as it should be in production), that's your public URL. When running locally without a proxy, the container listens on port `8080`.

## Session login (browsers)

```http
POST /api/auth/login
Content-Type: application/x-www-form-urlencoded

username=alice&password=s3cret
```

Response sets a `session` cookie. Subsequent requests from the same browser are authenticated automatically.

Log out:

```http
POST /api/auth/logout
```

For OIDC logins, hitting `/api/auth/logout` also triggers RP-Initiated Logout if your OIDC provider supports it (configured via `OIDC_END_SESSION_ENDPOINT`).

## HTTP Basic

Fine for quick scripts. Avoid in shared environments — the credentials are sent on every request.

```bash
curl -u alice:s3cret https://romm.example.com/api/roms
```

```python
import requests
from requests.auth import HTTPBasicAuth
r = requests.get("https://romm.example.com/api/roms",
                 auth=HTTPBasicAuth("alice", "s3cret"))
```

## OAuth2 Bearer token

The RomM backend implements the OAuth2 password grant. Exchange credentials for a short-lived access token and a refresh token:

```http
POST /api/token
Content-Type: application/x-www-form-urlencoded

grant_type=password&username=alice&password=s3cret&scope=roms.read%20roms.write
```

```json
{
  "access_token": "eyJhbGciOi...",
  "token_type": "bearer",
  "expires_in": 900,
  "refresh_token": "eyJhbGciOi..."
}
```

Access tokens are HS256-signed JWTs valid for ~15 minutes. Send them as:

```
Authorization: Bearer eyJhbGciOi...
```

Refresh before expiry:

```http
POST /api/token
Content-Type: application/x-www-form-urlencoded

grant_type=refresh_token&refresh_token=eyJhbGciOi...
```

Request only the scopes you need — RomM will issue a token with the intersection of what you asked for and what the user has.

## Client API tokens (for companion apps)

For anything long-lived — a running companion app, a cron job, a CI integration — use **Client API Tokens** instead of OAuth2. They're issued per-user from **Administration → Client API Tokens**, carry a subset of the user's scopes, and don't expire unless you set an expiry.

Token format: `rmm_` + 40 hex chars. Use it as a bearer:

```bash
curl -H "Authorization: Bearer rmm_abcdef0123456789..." \
     https://romm.example.com/api/roms
```

Each user gets up to 25 active tokens. Tokens can be paired with a device via the [pairing flow](../ecosystem/client-api-tokens.md) — useful when you don't want to type a long token on a handheld.

## OIDC

Users signing in through an OIDC provider get a regular RomM session, same as username/password login. For the API side this means you can't use an OIDC access token directly — authenticate the user through the browser first (they'll be redirected to the OIDC provider, then back to RomM), then use the resulting session cookie, **or** mint a Client API Token for programmatic use.

OIDC provider setup lives in [Administration → OIDC](../administration/oidc/index.md).

## Which scopes do I need?

Every endpoint in the [API Reference](api-reference.md) lists its required scopes. The short version:

- **Read**-ish endpoints want the matching `*.read` scope.
- **Write**-ish endpoints want `*.write`.
- **Admin** endpoints (anything under `/api/users` beyond `me`, `/api/tasks/run`) want `users.read`, `users.write`, or `tasks.run`.

A token that holds `users.write` also implicitly grants lesser scopes like `users.read` or `me.read` — RomM doesn't require you to list them all. But a token that holds only `roms.read` can't write, even if the underlying user is an Admin.

## Errors

| HTTP | Meaning |
| --- | --- |
| `401 Unauthorized` | No credential, expired credential, bad credential. |
| `403 Forbidden` | Authenticated, but the identity lacks a required scope. |
| `404 Not Found` | The resource doesn't exist — or, for privacy, the identity can't see it. |

When debugging a 403, check:

1. The **user's role** in Administration → Users.
2. The **token's scopes** (for OAuth2/Client API Tokens) — scopes are narrower than the user's role by default.
3. The endpoint's scope requirements in the [API Reference](api-reference.md).

## OpenAPI

The full machine-readable schema is served at `/openapi.json`. It's the source of truth for generated clients, Postman collections, and the in-docs [API Reference](api-reference.md).

```bash
curl https://romm.example.com/openapi.json > romm-openapi.json
```

See [Consuming OpenAPI](openapi.md) for codegen tips.