---
title: Set Border Size
description: "Play 0x5A, server → client."
---

`play` · `0x5A` · **clientbound** (server → client)

Sets the world border diameter immediately. The server sends it when the border size changes without animation.

Sent by the server, read by the client. Listen for it with `client.on("SetBorderSize", (data) => …)` on the receiving side.

## Fields

| Field | Type | Notes |
|---|---|---|
| `diameter` | Double |  |

## Send it

```ts
await client.sendPacket("SetBorderSize", {
  diameter: /* Double */,
});
```

Field aliases listed under Notes are accepted as alternative keys when writing.

Source: [`src/Core/Versions/776/Packets/play/clientbound/SetBorderSize.ts`](https://github.com/GDLev/mc-protocol/blob/master/src/Core/Versions/776/Packets/play/clientbound/SetBorderSize.ts)