> For the complete documentation index, see [llms.txt](https://ai-docs.fptcloud.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ai-docs.fptcloud.com/fpt-ai-studio/services/user-token/quickstart.md).
# Overview
#### **1. What It Is**
An **API Token Service** is a system or component that **issues, validates, and manages access tokens** for clients (users, apps, or other systems) to securely access APIs.
Instead of passing credentials each time, clients present a token — a short-lived credential — that proves their identity and permissions.
#### **2. Key Functions**
| Function | Description |
| --------------------------------- | ---------------------------------------------------------------------------------------------------- |
| **Token Issuance** | Generates access tokens (and optionally refresh tokens) after verifying the client or user identity. |
| **Token Validation** | Ensures a token is authentic, not expired, and has valid permissions before allowing API access. |
| **Token Revocation** | Invalidates tokens manually or automatically (e.g., if a user logs out or a secret is compromised). |
| **Scope & Permission Management** | Defines what resources or APIs a token can access. |
| **Auditing & Logging** | Tracks token usage, expiry, and potential abuse for security and compliance. |
#### **3. Benefits**
Increases API security (no password sharing)
Enables fine-grained access control via scopes/roles
Supports short-lived tokens (reduces breach risk)
Easy to revoke or rotate without impacting users
Scalable for multi-client or microservice environments
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