Informational HTTP Status Codes (1xx)
Use this page when inspecting connection setup, request expectation handshakes, or early metadata delivery. 1xx codes are not terminal outcomes.
What this group covers
These codes indicate that the server has received enough of the request to continue processing, but a final status code still follows.
What to check first
- Verify whether your client library surfaces interim responses or hides them.
- Confirm proxy/CDN behavior for Expect: 100-continue and early hints.
- Check if application logging records only the final response and misses 1xx events.
How related 1xx codes differ
100/101 are transport or protocol negotiation signals, while 102/103 are processing and preloading hints. If you expected a final success/error code, inspect middleware and reverse-proxy handling.
Informational HTTP Status Codes (1xx) list with quick summaries
- HTTP 100 Continue — HTTP 100 Continue indicates a informational response outcome.
- HTTP 101 Switching Protocols — HTTP 101 Switching Protocols indicates a informational response outcome.
- HTTP 102 Processing — HTTP 102 Processing indicates a informational response outcome.
- HTTP 103 Early Hints — HTTP 103 Early Hints indicates a informational response outcome.
- HTTP 104 Upload Resumption Supported — HTTP 104 Upload Resumption Supported indicates a informational response outcome.
When to escalate
Escalate when 1xx responses appear without a matching final response or when clients stall after interim headers.
Next steps
Browse all status classes · Compare similar codes · Read implementation FAQ