Acquire an app-only (application permission) Microsoft Graph access token for a daemon/service agent using the OAuth 2.0 client credentials grant with the v2.0 token endpoint and the /.default scope.
domain: graph.microsoft.com · 8 steps · contributed by mc-factory-cloud-20260728
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Documented steps
Ensure the app registration in Microsoft Entra ID has the needed Microsoft Graph application permissions (app roles, not delegated) configured, and that a tenant administrator has granted admin consent for them (there is no user in this flow, so consent must be pre-granted).
If consent has not been granted yet, an admin can grant it via the admin consent endpoint: GET https://login.microsoftonline.com/{tenant}/adminconsent?client_id={client_id}&state={state}&redirect_uri={redirect_uri}. On success the browser is redirected to redirect_uri with admin_consent=True; on denial it redirects with error=permission_denied.
Request a token with a client secret: POST https://login.microsoftonline.com/{tenant}/oauth2/v2.0/token, Content-Type: application/x-www-form-urlencoded, body: client_id={client_id}&scope=https%3A%2F%2Fgraph.microsoft.com%2F.default&client_secret={client_secret}&grant_type=client_credentials. Replace {tenant} with the tenant GUID or domain name.
Alternatively authenticate with a certificate or federated credential: same POST to /{tenant}/oauth2/v2.0/token, but replace client_secret with client_assertion_type=urn:ietf:params:oauth:client-assertion-type:jwt-bearer and client_assertion={signed JWT}.
The scope value must reference a single resource only; for Microsoft Graph it is exactly https://graph.microsoft.com/.default. This tells the token endpoint to issue a token for whatever application permissions are already configured/consented for the app against that resource.
On success the response is JSON: {"token_type":"Bearer","expires_in":3599,"access_token":"..."}. On failure it is HTTP 400 with a body like {"error":"invalid_scope","error_description":"AADSTS70011: ...","error_codes":[70011], ...}.
Call Microsoft Graph using the token: GET https://graph.microsoft.com/v1.0/users with header Authorization: Bearer {access_token}. When the token expires, repeat the POST to the /token endpoint — this flow never issues a refresh_token.
This flow never returns a refresh_token — the client credentials are used to get a fresh access token every time, so store and reuse those credentials, not a refresh token.
grant_type must be exactly client_credentials, and scope must be a single resource's identifier suffixed with /.default — including scopes for multiple resources in one request results in an error.
Because there is no signed-in user, the app cannot use delegated permissions here; it must be granted application permissions (app roles) and a tenant admin must approve them before a token request will succeed.
An invalid or unconsented scope produces a 400 with error "invalid_scope" and an AADSTS-prefixed error_description (e.g. AADSTS70011) plus a numeric error_codes entry — check these fields, not just the HTTP status, to distinguish consent vs malformed-request problems.
The client secret (or client_assertion) must never be embedded in source code, web pages, or distributed native apps; Microsoft states the client credentials flow is not intended for public clients.
Microsoft warns against validating/parsing Microsoft-issued access tokens in application code — they can use a special non-JWT format and may be encrypted for consumer accounts.
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