1xx Informational
HTTP 100 Continue
An interim response: the server has received the request headers and the client can go on and send the request body. Clients ask for it with an Expect: 100-continue header before a large upload, so they don’t send the body to a server that would refuse it anyway. The real status follows once the request is complete.
Defined in RFC 9110, section 15.2.1(opens in a new tab)
//_01 Uptime checks
Is 100 up or down for a monitor?
Uptimecheck HTTP monitor
Default settings
Not judged on its own. It is an interim response; the check waits for the final status that follows, and that one decides.
Is it down? checker
Free, at /is-it-down/
Not judged on its own. It is an interim response; the check waits for the final status that follows, and that one decides.
//_02 Causes and fixes
Why you see 100 and what to do
Typical causes
- A client sent Expect: 100-continue before an upload. curl does this for larger request bodies.
If you run the site
- Nothing to fix: it is part of a normal upload.
- If uploads hang, check that every proxy in front of the server passes the 100 Continue on, or answers the final status straight away.
If you’re a visitor
- You won’t see it in a browser. The final status code that follows is the one that matters.
Know the moment your site stops answering as it should
An Uptimecheck monitor requests your page as often as every minute, checks the status code against the ones you expect, confirms a failure with a second check and then alerts you.
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Questions
What does HTTP 100 mean?
An interim response: the server has received the request headers and the client can go on and send the request body. Clients ask for it with an Expect: 100-continue header before a large upload, so they don’t send the body to a server that would refuse it anyway. The real status follows once the request is complete.
Does an uptime monitor count 100 as down?
Not judged on its own. It is an interim response; the check waits for the final status that follows, and that one decides.
Downtime is obsolete.
Set up your first monitor in under a minute, or look around the live demo first.
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