2xx Success
HTTP 203 Non-Authoritative Information
The request succeeded, but a transforming proxy between the client and the server changed the content from what the origin server sent, for example by recompressing images. It tells the client the content isn’t exactly the origin’s. Rarely seen in practice.
Defined in RFC 9110, section 15.3.4(opens in a new tab)
//_01 Uptime checks
Is 203 up or down for a monitor?
Uptimecheck HTTP monitor
Default settings
Up. By default an Uptimecheck HTTP monitor accepts 200–399 as up, so a 203 counts as up. With a keyword check, the page must also contain the word you set.
Is it down? checker
Free, at /is-it-down/
Up: the checker counts any answer below 500 as the site answering.
//_02 Causes and fixes
Why you see 203 and what to do
Typical causes
- A proxy that modifies responses, such as a mobile network’s optimizing proxy.
If you run the site
- Nothing to fix on the origin. To stop proxies from changing content, send Cache-Control: no-transform.
If you’re a visitor
- Nothing to do.
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 203 mean?
The request succeeded, but a transforming proxy between the client and the server changed the content from what the origin server sent, for example by recompressing images. It tells the client the content isn’t exactly the origin’s. Rarely seen in practice.
Does an uptime monitor count 203 as down?
Up. By default an Uptimecheck HTTP monitor accepts 200–399 as up, so a 203 counts as up. With a keyword check, the page must also contain the word you set.
Downtime is obsolete.
Set up your first monitor in under a minute, or look around the live demo first.
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