Make programatic, automated actions on ad objects or Pages, or do programmatic ads buying. System users represent servers or software making API calls to assets owned or managed by a Business Manager.
The easiest, quickest way to create a system user is in the Business Manager tool. See Ads Help Center: How do I add a new System User.
To take actions for a person managing an ad account, you should take them through the standard Facebook oAuth flow and get a user access token. If you try to use system user tokens to work on ad objects or Pages on behalf of a real user of your software, you cannot link this user to those actions unless you take them through Facebook Login.
Learn about the two different types of system users: admin system user and system user. Read API limits for system users.
Guide: Create System Users
Create, retrieve, and update a system user. Learn how to invalidate access tokens.
A guide to install apps and generate access tokens through your system user.
Assign system user tasks on ad accounts, user page, and proxied assets. Retrieve permissions.
Guide: API Calls
How to make automated API calls for Marketing API and Pages API.
Rules for system users to operate with a Custom File Custom Audience.