> In order to access the client API endpoints you need to identify yourself. Unless you're using the `none` authentication method, you'll need to [create a CLIENT token](/how-to/how-to-create-api-tokens.mdx) and add an Authorization header using the token.
This endpoint is the one all clients should use to fetch all available feature flags from the _unleash-server_. The response returns all active feature flags and their current strategy configuration. A feature flag will have _at least_ one configured strategy. A strategy will have a `name` and `parameters` map.
> _Note:_ Clients should prefer the `strategies` property. Legacy properties (`strategy` & `parameters`) will be kept until **version 2** of the format.
This endpoint should never return anything besides a valid _20X or 304-response_. It will also include an `Etag`-header. The value of this header can be used by clients as the value of the `If-None-Match`-header in the request to prevent a data transfer if the client already has the latest response locally.
Used to fetch details about a specific feature flag. This is mainly provided to make it easy to debug the API and should not be used by the client implementations.
Strategy definitions may also contain a `constraints` property. Strategy constraints is a feature in Unleash which work on context fields, which is defined as part of the [Unleash Context](/reference/unleash-context.md). The purpose is to define a set of rules where all needs to be satisfied in order for the activation strategy to evaluate to true.
The example shows strategy constraints in action. Constraints is a new field on the strategy-object. It is a list of constraints that need to be satisfied.
In the example `environment` needs to be `production` AND `userId` must be either `123` OR `44` in order for the Unleash Client to evaluate the strategy, which in this scenario is “default” and will always evaluate to true.
```json
{
"type": "release",
"enabled": true,
"stale": false,
"name": "Demo",
"strategies": [
{
"constraints": [
{
"contextName": "environment",
"operator": "IN",
"values": ["production"]
},
{
"contextName": "userId",
"operator": "IN",
"values": ["123", "44"]
}
],
"name": "default",
"parameters": {}
}
]
}
```
- **contextName** - is the name of the field to look up on the unleash context.
- **values** - is a list of values (string).
- **operator** - is the logical action to take on the values Supported operator are:
- **IN** - constraint is satisfied if one of the values in the list matches the value for this context field in the context.
- **payload** - an optional object representing a payload to the variant. Takes two properties if present `type` and `value`.
- **overrides** - an optional array of overrides. If any context field matches any of the the defined overrides it means that the variant should be selected.
