---
title: API tokens and client keys
---

For Unleash to be of any use, it requires at least a server and a [consuming client](../sdks/index.md).
More advanced use cases may call for multiple clients, automated feature toggle updates, the [Unleash proxy](../sdks/unleash-proxy.md) and [Unleash proxy clients](../sdks/index.md#front-end-sdks), and more. To facilitate communication between all these moving parts, Unleash uses a system of API tokens and client keys, all with a specific purpose in mind.

This document details the three kinds of tokens and keys that you will need to fully connect any Unleash system:
- [Admin tokens](#admin-tokens) for updating resources in Unleash
- [Client tokens](#client-tokens) for connecting server-side client SDKs and the Unleash proxy to the Unleash server
- [Proxy client keys](#proxy-client-keys) for connecting proxy client SDKs to the Unleash proxy.

## API tokens

:::tip
This section describes what API tokens are. For information on how to create them, refer to the [how-to guide for creating API tokens](../user_guide/token.md).
:::

Use API tokens to connect to the Unleash server API. API tokens come in two distinct types:
- [Admin tokens](#admin-tokens)
- [Client tokens](#client-tokens)

Both types use [the same format](#format) but have different intended uses. API tokens are considered to be *secrets* and should _not_ be exposed to end users.

### Admin tokens

**Admin tokens** grant *full read and write access* to all resources in the Unleash server API. Admin tokens have access to all projects, all environments, and all global resources (find out more about [resources in the RBAC document](../user_guide/rbac.md#core-principles)).

Use admin tokens to:
- Automate Unleash behavior such as creating feature toggles, projects, etc.
- Write custom Unleash UIs to replace the default Unleash admin UI.

Do **not** use admin tokens for:
- [Client SDKs](../sdks/index.md): You will _not_ be able to read toggle data from multiple environments. Use [client tokens](#client-tokens) instead.

Support for scoped admin tokens with more fine-grained permissions is currently in the planning stage.

### Client tokens

**Client tokens** are intended for use in [server-side client SDKs](../sdks/index.md#server-side-sdks) (including the Unleash Proxy) and grant the user permissions to:
- Read feature toggle information
- Register applications with the Unleash server
- Send usage metrics

When creating a client token, you can choose which projects it should be able to read data from. You can give it access to a specific list of projects or to all projects (including projects that don't exist yet). Prior to Unleash 4.10, a token could be valid only for a *single project* or *all projects*.

Each client token is only **valid for a single environment**.

Use client tokens:
- In [server-side client SDKs](../sdks/index.md#server-side-sdks)
- To connect [the Unleash Proxy](../sdks/unleash-proxy.md) to the Unleash API

Do **not** use client tokens in:
- [Front-end SDKs](../sdks/index.md#front-end-sdks). You will _not_ be able to connect to the Unleash server due to CORS restrictions. Configure an [Unleash Proxy](../sdks/unleash-proxy.md) and use [Proxy client keys](#proxy-client-keys) instead.

### Format

API tokens come in one of two formats. When we introduced [environments](../user_guide/environments.md) in Unleash 4.3, we updated the format of the tokens to provide more human-readable information to the user. Both formats are still valid (you don't need to update a working token of the old format) and are described below.

#### Version 1

The first version of API tokens was a 64 character long hexadecimal string. Example:

```
be44368985f7fb3237c584ef86f3d6bdada42ddbd63a019d26955178
```


#### Version 2

API tokens consist of three parts:

1. Project(s)
2. Environment
3. Hash

The parts are separated by two different separators: A colon (`:`) between the project(s) and the environment, and a full stop (`.`) between the environment and the hash.

The **project(s)** part is one of:
- The id of a specific project, for example: `default`. This indicates that the token is **only valid for this project**.
- A pair of opening and closing square brackets: `[]`. This indicates that the token is **valid for a discrete list of projects**. The list of projects is not shown in the token.
- An asterisk: `*`. This indicates that the token is **valid for all projects (current and future)**.

The **environment** is the name of an environment on your Unleash server, such as `development`.

The **hash** is 64 character long hexadecimal string.

Some example client tokens are:
- A token with access to toggles in the "development" environment of a single project, "project-a":
  ```
  project-a:development.be44368985f7fb3237c584ef86f3d6bdada42ddbd63a019d26955178
  ```
- A token with access to toggles in the "production" environment multiple projects:
  ```
  []:production.be44368985f7fb3237c584ef86f3d6bdada42ddbd63a019d26955178
  ```
- A token with access to toggles in the "development" environment of all projects:
  ```
  *:development.be44368985f7fb3237c584ef86f3d6bdada42ddbd63a019d26955178
  ```

## Proxy client keys {#proxy-client-keys}

Use proxy client keys to connect [Proxy client SDKs (front-end SDKs)](../sdks/index.md#front-end-sdks) to the [Unleash Proxy](../sdks/unleash-proxy.md). As opposed to the [API tokens](#api-tokens), Proxy client keys are *not* considered secret and are safe to use on any clients (refer to the [the proxy documentation for more about privacy](../sdks/unleash-proxy.md#we-care-about-privacy)). They do _not_ let you connect to the Unleash server API.

Proxy client keys are arbitrary strings that you *must* provide the Unleash proxy with on startup. Unleash does not generate proxy client keys for you. Because of this, they have no specific format.

Use Proxy client keys to:
- Connect [Proxy client SDKs](../sdks/index.md#front-end-sdks) to the [Unleash Proxy](../sdks/unleash-proxy.md)
- Connect your own custom Proxy clients (or pure HTTP requests) to the Unleash Proxy

Do **not** use Proxy client keys to:
- Connect to the Unleash API. It will not work. Use an appropriate [API token](#api-tokens) instead.
