microsoft/playwright · error · Error

Unexpected buffer type of 'data.${name}'

Error message

Unexpected buffer type of 'data.${name}'

What it means

Error "Unexpected buffer type of 'data.${name}'" thrown in microsoft/playwright.

Source

Thrown at packages/playwright-core/src/client/fetch.ts:287

    });
  }

  async storageState(options: { path?: string, indexedDB?: boolean } = {}): Promise<StorageState> {
    const state = await this._channel.storageState({ indexedDB: options.indexedDB }, kNoTimeout);
    if (options.path) {
      await mkdirIfNeeded(options.path);
      await fs.promises.writeFile(options.path, JSON.stringify(state, undefined, 2), 'utf8');
    }
    return state;
  }
}

async function toFormField(name: string, value: string | number | boolean | fs.ReadStream | FilePayload): Promise<channels.FormField> {
  const typeOfValue = typeof value;
  if (isFilePayload(value)) {
    const payload = value as FilePayload;
    if (!Buffer.isBuffer(payload.buffer))
      throw new Error(`Unexpected buffer type of 'data.${name}'`);
    return { name, file: filePayloadToJson(payload) };
  } else if (typeOfValue === 'string' || typeOfValue === 'number' || typeOfValue === 'boolean') {
    return { name, value: String(value) };
  } else {
    return { name, file: await readStreamToJson(value as fs.ReadStream) };
  }
}

function isJsonParsable(value: any) {
  if (typeof value !== 'string')
    return false;
  try {
    JSON.parse(value);
    return true;
  } catch (e) {
    if (e instanceof SyntaxError)
      return false;
    else

View on GitHub (pinned to c8fc3bf8d3)

When it happens

Trigger: Thrown at packages/playwright-core/src/client/fetch.ts:287 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of microsoft/playwright@c8fc3bf8d3 (2026-08-12). Data as JSON: /api/errors/daed2b4a86502a89. Report an issue: GitHub.