# Method signature MeetMainStageClient.notifySidePanel

Sends a message from the main stage add-on iframe to the side panel add-on
iframe. The add-on running in the side panel iframe can react to this message
using the
[`frameToFrameMessage`](https://developers.google.com/workspace/meet/add-ons/reference/websdk/addon_sdk.addoncallbacks.frametoframemessage)
add-on callback. The length of this string must be less than 1,000,000
characters.

## Signature

    notifySidePanel(payload: string): Promise<void>;

## Details

| Optional | No |
|---|---|

## Parameters

| Name | Type | Optional | Description |
|---|---|---|---|
| `payload` | `string` | No |   |

## Returns

`Promise<void>`