microsoft/playwright · error · Error

POST data is not a valid JSON object: ' + postData

Error message

POST data is not a valid JSON object: ' + postData

What it means

Error "POST data is not a valid JSON object: ' + postData" thrown in microsoft/playwright.

Source

Thrown at packages/playwright-core/src/client/network.ts:164

  postDataJSON(): Object | null {
    const postData = this.postData();
    if (!postData)
      return null;

    const contentType = this.headers()['content-type'];
    if (contentType?.includes('application/x-www-form-urlencoded')) {
      const entries: Record<string, string> = {};
      const parsed = new URLSearchParams(postData);
      for (const [k, v] of parsed.entries())
        entries[k] = v;
      return entries;
    }

    try {
      return JSON.parse(postData);
    } catch (e) {
      throw new Error('POST data is not a valid JSON object: ' + postData);
    }
  }

  /**
   * @deprecated
   */
  headers(): Headers {
    if (this._fallbackOverrides.headers)
      return RawHeaders._fromHeadersObjectLossy(this._fallbackOverrides.headers).headers();
    return this._provisionalHeaders.headers();
  }

  async _actualHeaders(): Promise<RawHeaders> {
    if (this._fallbackOverrides.headers)
      return RawHeaders._fromHeadersObjectLossy(this._fallbackOverrides.headers);

    if (!this._actualHeadersPromise) {
      this._actualHeadersPromise = this._wrapApiCall(async () => {

View on GitHub (pinned to c8fc3bf8d3)

When it happens

Trigger: Thrown at packages/playwright-core/src/client/network.ts:164 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/1fd9ecfa2323488f. Report an issue: GitHub.