HTTP 100 — Continue
1xx Informational
What it means
The client sent an Expect: 100-continue header and the server is telling it to go ahead and send the request body.
What to do about it
Nothing to fix — this is a normal handshake used to avoid uploading a large body that would be rejected anyway.
Where it sits
100 belongs to the 1xx family: The request was received and the process is continuing. These are rarely seen by application code.
HTTP/1.1 100 ContinueChecking it yourself
# see the status code and headers only
curl -sI https://example.com/path
# follow redirects and print each hop
curl -sIL -o /dev/null -w "%{http_code} %{url_effective}\n" https://example.com/path
# JavaScript
const r = await fetch(url);
console.log(r.status, r.statusText);How this code behaves
| Cacheable by default | No — caches must not store this response unless explicit cache headers permit it. |
| Safe to retry | Not applicable. |
| Effect on search indexing | No direct effect. |
Returning 100 correctly
# nginx
return 100;
# Express
res.status(100).json({ error: 'Continue' });
# Go
w.WriteHeader(100)
# Python (Flask)
return jsonify(error='Continue'), 100;Frequently asked questions
What does HTTP 100 mean?
The client sent an Expect: 100-continue header and the server is telling it to go ahead and send the request body.
How do I fix a 100 error?
Nothing to fix — this is a normal handshake used to avoid uploading a large body that would be rejected anyway.
Is 100 a client or server problem?
Neither — it indicates success or progress.