OAuth2 & OpenID Connect Deep Dive · Lesson

Device Authorization Grant

Learn the OAuth2 Device Authorization Grant (RFC 8628) used by input-constrained devices such as smart TVs, consoles, and CLI tools to obtain tokens via a secondary device.

Device Authorization Grant is a free OAuth2 & OpenID Connect Deep Dive lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the OAuth2 & OpenID Connect Deep Dive learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Why a Device Grant?

Some clients have no browser or only a limited keypad: smart TVs, media consoles, printers, and CLI tools. The classic Authorization Code Flow assumes a rich browser for the user-agent redirect, which these devices cannot provide.

The Device Authorization Grant (RFC 8628) solves this by letting the user complete authorization on a second device (phone or laptop) while the constrained device polls for the result.

The Two Endpoints

The flow introduces a new device authorization endpoint alongside the standard token endpoint.

/device_authorization — the device requests codes here.
/token — the device polls here with grant type urn:ietf:params:oauth:grant-type:device_code.

No redirect URI is involved at all.

Step 1: Requesting Device Codes

The device makes a POST to the device authorization endpoint with its client_id and desired scope.

POST /device_authorization HTTP/1.1
Host: auth.example.com
Content-Type: application/x-www-form-urlencoded

client_id=tv-app-123&scope=profile email

Step 2: The Response

The server returns a device_code (used by the machine), a user_code (typed by the human), a verification_uri, an expires_in, and an interval for polling.

{
  "device_code": "GmRhmhcxhwAzkoEqiMEg",
  "user_code": "WDJB-MJHT",
  "verification_uri": "https://example.com/device",
  "expires_in": 900,
  "interval": 5
}

Step 3: User Instructions

The device displays a short message: Go to example.com/device and enter code WDJB-MJHT.

A verification_uri_complete may also be returned, embedding the code so a QR code can carry the whole link.

Step 4: User Authorizes

On their phone or laptop, the user opens the verification URI, logs in, enters the user_code, and approves the requested scopes. This happens in a full browser, so MFA and rich consent screens all work normally.

Step 5: Device Polls the Token Endpoint

Meanwhile the device polls the token endpoint at the given interval, sending the device_code.

POST /token HTTP/1.1
Host: auth.example.com
Content-Type: application/x-www-form-urlencoded

grant_type=urn:ietf:params:oauth:grant-type:device_code
&device_code=GmRhmhcxhwAzkoEqiMEg
&client_id=tv-app-123

Polling Responses

Until the user finishes, the server returns errors that tell the device how to behave:

authorization_pending — keep polling, user has not approved yet.
slow_down — increase the interval by 5 seconds.
access_denied — user rejected; stop.
expired_token — codes expired; restart.

Step 6: Success

Once the user approves, the next poll returns a normal token response with an access_token (and optionally a refresh_token), exactly like other grants.

{
  "access_token": "eyJhbGciOi...",
  "token_type": "Bearer",
  "expires_in": 3600,
  "refresh_token": "8xLOxBtZp8"
}

A Simple Poll Loop

A pseudo-implementation of the polling logic, respecting slow_down:

let interval = 5;
while (true) {
  await sleep(interval * 1000);
  const res = await pollToken(deviceCode);
  if (res.access_token) return res;
  if (res.error === 'slow_down') interval += 5;
  else if (res.error === 'authorization_pending') continue;
  else throw new Error(res.error);
}

Security Considerations

Keep user_codes short but high-entropy to resist brute force, and rate-limit the verification page. Because there is no redirect, phishing risk shifts to the verification URI — always show the user exactly which app and scopes they are approving.

Quick Check

Test your understanding of the device grant.

Recap

The Device Authorization Grant lets browserless devices authenticate users via a second device.

Device gets a device_code + user_code from the device endpoint.
User approves on a phone/laptop at the verification URI.
Device polls the token endpoint, handling authorization_pending and slow_down.
On approval it receives normal access and refresh tokens.

Frequently asked questions

Is the “Device Authorization Grant” lesson free?

Yes — the full text of “Device Authorization Grant” is free to read here on the web, and the OAuth2 & OpenID Connect Deep Dive course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the OAuth2 & OpenID Connect Deep Dive course, upgrade to CoddyKit PRO.

What will I learn in “Device Authorization Grant”?

Learn the OAuth2 Device Authorization Grant (RFC 8628) used by input-constrained devices such as smart TVs, consoles, and CLI tools to obtain tokens via a secondary device. You practise OAuth2 & OpenID Connect Deep Dive with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start OAuth2 & OpenID Connect Deep Dive?

No prior experience is required. OAuth2 & OpenID Connect Deep Dive on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Device Authorization Grant” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this OAuth2 & OpenID Connect Deep Dive lesson?

Yes. Every OAuth2 & OpenID Connect Deep Dive lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

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