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CodeSandbox Not Loading or Not Starting

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Ongoing Web Updated November 14, 2026Based on 2 user reportsHow we research

Quick answer

A sandbox that never starts is often blocked by a firewall or network filter, or by a frozen VM. Allowlist the CodeSandbox domains and check your credits.

Most likely fix: Allowlist CodeSandbox domains

How to fix it

Try these in order — the most common fix is first.

  1. 1. Allowlist CodeSandbox domains

    1. Ask your network admin (or check your firewall) to allow codesandbox.io, *.csb.app and worker.codesandbox.io
    2. Reload the sandbox
    Did this fix it?

  2. 2. Check credits and VM state

    1. Open the workspace usage page and confirm credits remain
    2. If the VM is frozen, upgrade, raise the spending limit, or wait for the next billing cycle
    Did this fix it?

  3. 3. Rule out the browser

    1. Try a private window with extensions off
    2. Clear site data for codesandbox.io and reload
    Did this fix it?

Symptoms

The editor or preview spins forever, the sandbox never boots, or the VM stays on starting.

Why it happens

  • Firewall, school or company network blocking CodeSandbox domains
  • VM frozen because credits ran out
  • Temporary service disruption
  • Browser extensions or cached data interfering

This guide also covers

  • codesandbox not loading
  • codesandbox stuck on starting
  • why is codesandbox not working

Still not working?

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