> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mainwp.com/llms.txt
> Use this file to discover all available pages before exploring further.

# How MainWP Syncs with Child Sites

> Learn how MainWP Dashboard communicates with Child Sites via HTTPS requests using cURL. Understand the sync process, OpenSSL encryption, and asymmetric cryptography that secures the connection between your Dashboard and sites.

MainWP Dashboard communicates with child sites by executing HTTPS requests using [cURL](https://www.php.net/manual/en/intro.curl.php). Each sync request contains three required parameters:

| Parameter            | Purpose                                                           |
| -------------------- | ----------------------------------------------------------------- |
| **Username**         | Administrator username for establishing the secure connection     |
| **Function**         | Name of the function to execute on the child site                 |
| **MainWP Signature** | Authentication signature. If it doesn't match, the request fails. |

## Example Sync Request

```
https://childsite.com/wp-admin/admin-ajax.php?user=demouser&function=stats&mainwpsignature=dgTOIUbQyBWvCh0pNhnwmxmHoeayfg34...
```

This request executes the `stats` function after authentication. The sync request passes data from Dashboard to child sites, including settings like Abandoned Plugins/Themes tolerance (`&numberdaysOutdatePluginTheme=365`).

<Note>
  Some MainWP settings require syncing after changes because the sync request sets values on child sites.
</Note>

## Extension Data in Sync Requests

MainWP provides the `mainwp-sync-others-data` hook for extensions to include data in sync requests. The `othersData` parameter contains encoded data for plugins like BackWPup, BackupWordPress, BackupBuddy, Client Reports, WP Staging, WP Time Capsule, UpdraftPlus, Page Speed, and WP Rocket.

## What the Sync Process Retrieves

The sync request executes `get_site_stats()` in the MainWP Child plugin (via `&function=stats`). This function fetches information from child sites and passes it to your Dashboard:

* Available updates for plugins, themes, and WordPress core
* Potentially abandoned plugins/themes
* Site health data
* Extension-specific data

## Performance Considerations

Synchronizing with child sites requires CPU resources, so you may see a brief spike in CPU usage on your Dashboard server.

If sync operations cause availability issues for other sites on the same server:

* Increase server resources
* Decrease **Maximum simultaneous sync requests** at **MainWP > Settings > Advanced Settings** (increases sync time but reduces CPU load)

## Sync Request Security

When MainWP Dashboard first connects to a child site, it generates a 2048-bit public/private key pair using the `openssl_pkey_new()` function. The public key is stored on the child site; the private key is stored on the Dashboard.

| Step           | Function           | Location            |
| -------------- | ------------------ | ------------------- |
| Sign request   | `openssl_sign()`   | MainWP Dashboard    |
| Verify request | `openssl_verify()` | MainWP Child plugin |

The Dashboard signs each request with the private key. The Child plugin verifies the signature using the public key. Requests with invalid signatures are rejected.

## How Asymmetric Cryptography Works

Asymmetric encryption uses key pairs where one key encrypts data and only the other key can decrypt it.

**Example:** John wants to send sensitive data to Alice.

1. John encrypts the data using Alice's public key
2. Only Alice has the corresponding private key
3. Only Alice can decrypt the data back to its original form
4. Even if someone intercepts the encrypted data, they cannot read it without Alice's private key

MainWP uses this principle: the Dashboard signs requests with its private key, and child sites verify them with the corresponding public key. This ensures requests genuinely come from your authorized Dashboard.