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Per-message compression can be enabled with the perMessageDeflate parameter. When set, all messages will be compressed using the permessage-deflate WebSocket extension.
https://mintcdn.com/bun-1dd33a4e-claude-docs-bunfig-missing-fields/ezY9cqHIbAlx71jp/icons/typescript.svg?fit=max&auto=format&n=ezY9cqHIbAlx71jp&q=85&s=fa9c9d5f512d0d81ae41ed65741d389aserver.ts
Bun.serve({
  // ...
  websocket: {
    // enable compression
    perMessageDeflate: true,
  },
});

To enable compression for individual messages, pass true as the second parameter to ws.send().
https://mintcdn.com/bun-1dd33a4e-claude-docs-bunfig-missing-fields/ezY9cqHIbAlx71jp/icons/typescript.svg?fit=max&auto=format&n=ezY9cqHIbAlx71jp&q=85&s=fa9c9d5f512d0d81ae41ed65741d389aserver.ts
Bun.serve({
  // ...
  websocket: {
    async message(ws, message) {
      // send a compressed message
      ws.send(message, true);
    },
  },
});