WebCrawler API

Why are Firefox headful runs on Ubuntu flaky in Puppeteer?

Puppeteer

Summary

The startup hang in headful mode on Ubuntu was caused by the Firefox Backup Service during startup. A practical workaround is to disable the Backup Service by setting the Firefox preference browser.backup.enabled to false.

Workaround options

Use a Firefox profile with the preference set in user.js:

// firefox profile file: user.js
user_pref("browser.backup.enabled", false);

Pass the preference directly when launching via Puppeteer. The exact option name depends on the Puppeteer version:

const browser = await puppeteer.launch({
  product: 'firefox',
  headless: false,
  firefoxUserPrefs: {
    'browser.backup.enabled': false,
  },
});

const browser = await puppeteer.launch({
  product: 'firefox',
  headless: false,
  extraPrefsFirefox: {
    'browser.backup.enabled': false,
  },
});

Notes

  • This is a targeted workaround for startup hangs observed in headful Firefox on Linux runners.
  • A broader long-term fix involved disabling the backup service in Firefox builds, but setting the preference per profile or per launch is the fastest practical fix.
  • If you are not using a custom profile, creating one with user.js and pointing Firefox to it is usually the most reliable path.