Problem Description
Some users may face the following error while accessing a website that is using Cloudflare DNS/CDN:
Error:ERR_QUIC_PROTOCOL_ERROR
This error usually appears in Google Chrome and may cause the website to load slowly, fail to open, or show as offline even though the server is working fine.
Root Cause
Cloudflare enables HTTP/3 (QUIC) by default to improve performance.
However, in some environments (ISPs, firewalls, browsers, or networks), QUIC protocol can cause compatibility issues, resulting in the ERR_QUIC_PROTOCOL_ERROR.
Solution (Recommended Fix)
You can resolve this issue by disabling HTTP/3 (QUIC) in Cloudflare.
Steps to Disable HTTP/3 (QUIC)
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Log in to your Cloudflare Dashboard
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Select the affected Domain
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Go to Speed from the left menu
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Click on Settings
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Open the Protocol Optimization tab
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Locate the option:
HTTP/3 (with QUIC) -
Turn OFF this option
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Save the changes
Once disabled, Cloudflare will fall back to HTTP/2, which is more stable across all networks.
Result
After disabling HTTP/3 (QUIC):
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ERR_QUIC_PROTOCOL_ERROR is resolved
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Website loads normally
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No impact on DNS or SSL
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Improved compatibility for all users
Additional Notes
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This issue is not related to server performance
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No changes are required on the hosting server
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You can re-enable HTTP/3 later if your network fully supports it
Still Facing Issues?
If the problem persists after disabling HTTP/3, please contact our support team with:
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Website URL
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Browser name & version
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Screenshot of the error
We’ll be happy to assist you further.