> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.getunleash.io/api/register-client-application/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.getunleash.io/_mcp/server.

# Register a client SDK

POST https://app.unleash-instance.example.com/api/client/register
Content-Type: application/json

Register a client SDK with Unleash. SDKs call this endpoint on startup to tell Unleash about their existence. Used to track custom strategies in use as well as SDK versions.

Reference: https://docs.getunleash.io/api/register-client-application

## Authentication

- `Authorization` header (required) — API key needed to access this API
- `Authorization` header (bearer token, required) — API key needed to access this API, in Bearer token format

## Request

### Body (application/json)

This endpoint expects a clientApplicationSchema.

- `appName` (string, required) — An identifier for the app that uses the sdk, should be static across SDK restarts
- `interval` (double, required) — How often (in seconds) does the client refresh its toggles
- `started` (ClientApplicationSchemaStarted, required) — Either an RFC-3339 timestamp or a unix timestamp in seconds
- `strategies` (list of string, required) — Which strategies the SDKs runtime knows about
- `instanceId` (string, optional) — A unique identifier identifying the instance of the application running the SDK. Often changes based on execution environment. For instance: two pods in Kubernetes will have two different instanceIds
- `sdkVersion` (string, optional) — An SDK version identifier. Usually formatted as "unleash-client-\<language>:\<version>"
- `platformName` (string, optional) — The platform the application is running on. For languages that compile to binaries, this can be omitted
- `platformVersion` (string, optional) — The version of the platform the application is running on. Languages that compile to binaries, this is expected to be the compiler version used to assemble the binary.
- `yggdrasilVersion` (string, optional) — The semantic version of the Yggdrasil engine used by the client. If the client is using a native engine this can be omitted.
- `specVersion` (string, optional) — The version of the Unleash client specification the client supports
- `sdkFlavor` (string, optional) — The identifier of an integration built on top of an Unleash SDK (e.g. an OpenFeature provider). Sent so adoption of the integration can be tracked alongside sdkVersion.
- `sdkFlavorVersion` (string, optional) — The version of the integration identified by sdk flavor, that has been built on top of an Unleash SDK

## Response

### 202

This response has no body.

## Types

### ClientApplicationSchemaStarted

Either an RFC-3339 timestamp or a unix timestamp in seconds

## Examples

**Request**

```json
{
  "appName": "example-app",
  "interval": 10,
  "started": "2023-06-13T16:35:00.000Z",
  "strategies": [
    "default",
    "gradualRollout",
    "remoteAddress"
  ]
}
```

**Response**

```json
{}
```

**SDK Code**

```python
import requests

url = "https://app.unleash-instance.example.com/api/client/register"

payload = {
    "appName": "example-app",
    "interval": 10,
    "started": "2023-06-13T16:35:00.000Z",
    "strategies": ["default", "gradualRollout", "remoteAddress"]
}
headers = {
    "Authorization": "<apiKey>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.json())
```

```javascript
const url = 'https://app.unleash-instance.example.com/api/client/register';
const options = {
  method: 'POST',
  headers: {Authorization: '<apiKey>', 'Content-Type': 'application/json'},
  body: '{"appName":"example-app","interval":10,"started":"2023-06-13T16:35:00.000Z","strategies":["default","gradualRollout","remoteAddress"]}'
};

try {
  const response = await fetch(url, options);
  const data = await response.json();
  console.log(data);
} catch (error) {
  console.error(error);
}
```

```go
package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://app.unleash-instance.example.com/api/client/register"

	payload := strings.NewReader("{\n  \"appName\": \"example-app\",\n  \"interval\": 10,\n  \"started\": \"2023-06-13T16:35:00.000Z\",\n  \"strategies\": [\n    \"default\",\n    \"gradualRollout\",\n    \"remoteAddress\"\n  ]\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "<apiKey>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(res)
	fmt.Println(string(body))

}
```

```ruby
require 'uri'
require 'net/http'

url = URI("https://app.unleash-instance.example.com/api/client/register")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = '<apiKey>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"appName\": \"example-app\",\n  \"interval\": 10,\n  \"started\": \"2023-06-13T16:35:00.000Z\",\n  \"strategies\": [\n    \"default\",\n    \"gradualRollout\",\n    \"remoteAddress\"\n  ]\n}"

response = http.request(request)
puts response.read_body
```

```java
import com.mashape.unirest.http.HttpResponse;
import com.mashape.unirest.http.Unirest;

HttpResponse<String> response = Unirest.post("https://app.unleash-instance.example.com/api/client/register")
  .header("Authorization", "<apiKey>")
  .header("Content-Type", "application/json")
  .body("{\n  \"appName\": \"example-app\",\n  \"interval\": 10,\n  \"started\": \"2023-06-13T16:35:00.000Z\",\n  \"strategies\": [\n    \"default\",\n    \"gradualRollout\",\n    \"remoteAddress\"\n  ]\n}")
  .asString();
```

```php
<?php
require_once('vendor/autoload.php');

$client = new \GuzzleHttp\Client();

$response = $client->request('POST', 'https://app.unleash-instance.example.com/api/client/register', [
  'body' => '{
  "appName": "example-app",
  "interval": 10,
  "started": "2023-06-13T16:35:00.000Z",
  "strategies": [
    "default",
    "gradualRollout",
    "remoteAddress"
  ]
}',
  'headers' => [
    'Authorization' => '<apiKey>',
    'Content-Type' => 'application/json',
  ],
]);

echo $response->getBody();
```

```csharp
using RestSharp;

var client = new RestClient("https://app.unleash-instance.example.com/api/client/register");
var request = new RestRequest(Method.POST);
request.AddHeader("Authorization", "<apiKey>");
request.AddHeader("Content-Type", "application/json");
request.AddParameter("application/json", "{\n  \"appName\": \"example-app\",\n  \"interval\": 10,\n  \"started\": \"2023-06-13T16:35:00.000Z\",\n  \"strategies\": [\n    \"default\",\n    \"gradualRollout\",\n    \"remoteAddress\"\n  ]\n}", ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
```

```swift
import Foundation

let headers = [
  "Authorization": "<apiKey>",
  "Content-Type": "application/json"
]
let parameters = [
  "appName": "example-app",
  "interval": 10,
  "started": "2023-06-13T16:35:00.000Z",
  "strategies": ["default", "gradualRollout", "remoteAddress"]
] as [String : Any]

let postData = JSONSerialization.data(withJSONObject: parameters, options: [])

let request = NSMutableURLRequest(url: NSURL(string: "https://app.unleash-instance.example.com/api/client/register")! as URL,
                                        cachePolicy: .useProtocolCachePolicy,
                                    timeoutInterval: 10.0)
request.httpMethod = "POST"
request.allHTTPHeaderFields = headers
request.httpBody = postData as Data

let session = URLSession.shared
let dataTask = session.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
  if (error != nil) {
    print(error as Any)
  } else {
    let httpResponse = response as? HTTPURLResponse
    print(httpResponse)
  }
})

dataTask.resume()
```