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Home / browser-issues / How to Fix Cloudflare 521 Error on Apache Servers - Troubleshooting DNS Probe Finished NXDOMAIN on Custom Servers-Fix Node.js Heap Out of Memory: Practical Steps

How to Fix Cloudflare 521 Error on Apache Servers - Troubleshooting DNS Probe Finished NXDOMAIN on Custom Servers-Fix Node.js Heap Out of Memory: Practical Steps

2026-07-28 09:13:53browser-issues
How to Fix Cloudflare 521 Error on Apache Servers - Troubleshooting DNS Probe Finished NXDOMAIN on Custom Servers-Fix Node.js Heap Out of Memory: Practical Steps

Final checklist

  • Confirm that the same symptom is gone after a restart or refresh.
  • Keep the smallest working change and undo temporary diagnostic settings.