# Limited Links
Limited links is a feature that allows you to restrict the number of devices that can add a subscription (link) to the application.\
In your personal account on the `happ-proxy.com` website, you specify your subscription URL, set the maximum number of devices, and click "Generate link."\
The resulting link can be shared with a user, and you can be confident that the subscription can only be installed on the specified number of devices — exceeding the limit is impossible.
You can create limited links both through the web interface and via API.
**Creating via Website**
1. On the creation page, specify the **unencrypted URL** of your subscription.
2. Set the **installation limit** (maximum number of devices).
3. After generation:
* The **InstallID** parameter is automatically added to the URL.
* The link domain is stored in the database as a **SHA-256 hash** (raw domains are not stored to enhance security).
You will receive an **encrypted link** with the InstallID parameter.
***
**Creating via API**
Send a GET request to:
```
https://api.happ-proxy.com/api/add-install?
provider_code={provider_code}&
auth_key={auth_key}&
install_limit={install_limit}
```
* **{provider\_code}** — your provider code (in your profile)
* **{auth\_key}** — authorization key (in your profile)
* **{install\_limit}** — maximum number of devices
**API Response**
* **Success**
```json
{
"rc": 1,
"msg": "Ok",
"install_code": "6P0hVao1fG5e"
}
```
* **Error**
```json
{
"rc": 0,
"msg": "Error description"
}
```
Add the received **install\_code** to the link as the **InstallID** parameter.
***
**Example**
* Original URL:
```
https://url.com/sub
```
* Final link:
```
https://url.com/sub#Your_TITLE?installid=Abcd1234
```
> **Tip:** Encrypt the link so users cannot remove the InstallID parameter.
***
**How It Works**
When adding a link, the application calculates the SHA-256 hash of the domain and sends a request to:
```
https://check.happ-proxy.com/install?id={domain_hash}&installid={InstallID}
```
The response returns `ProviderID` and link status.
If the request fails to send (e.g., due to website blocking), the application will automatically retry after establishing a VPN connection.
The `happ-proxy.com` server receives the device's `HWID` and responds positively if the installation limit for the link has not been exceeded. If the limit is exceeded, the server returns a refusal and the application displays the message:\
\&#xNAN;**"The subscription administrator has restricted access. Please contact technical support."**
---
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Perform an HTTP GET request on the current page URL with the `ask` query parameter:
```
GET https://www.happ.su/main/dev-docs/limited-links.md?ask=
```
The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.
