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curle_http3
Moderate
cURL · libcurl & CLI
libcurl code CURLE_HTTP3 indicates http3 during TLS/HTTP protocol negotiation.
Quick Answer
Error code CURLE_HTTP3 on your cURL libcurl & CLI means: libcurl code CURLE_HTTP3 indicates http3 during TLS/HTTP protocol negotiation.. This is usually fixable — see the step-by-step guide below.
Affected Models
Applies to all models
LIBCURL-EMBED7.797.817.847.888.08.28.48.68.8LINUX-CLIMACOS-CLI
Likely Causes
  1. CURLE_HTTP3 was returned while libcurl handled a request stage related to TLS/HTTP protocol negotiation.
  2. Command options, endpoint behavior, or intermediary network components are incompatible with expected transfer flow.
  3. Runtime environment specifics (proxy, cert store, protocol support, or callback behavior) contributed to CURLE_HTTP3.
How to Fix It
1
Capture verbose output (-v / --trace) and isolate the exact phase where CURLE_HTTP3 appears.
2
Reproduce http3 with a minimal request against a known-good endpoint.
3
Validate protocol, TLS, DNS, proxy, and timeout options tied to TLS/HTTP protocol negotiation.
4
Adjust one option at a time until CURLE_HTTP3 clears and transfer completes successfully.
5
Lock the fix into scripts/clients and monitor for CURLE_HTTP3 regression.
Pro Tip
This fix requires some technical knowledge. If you're unsure about any step, consider contacting support or a qualified technician.
Related Error Codes
CURLE_ABORTED_BY_CALLBACKCURLE_AGAINCURLE_AUTH_ERRORCURLE_BAD_CONTENT_ENCODINGCURLE_BAD_DOWNLOAD_RESUME
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