Are preflight OPTIONS requests not handled automat...
# ktors
S.
08/15/2025, 3:09 PMAre preflight OPTIONS requests not handled automatically by a ktor server? both safari and firefox preflights are answered with 403
✅ 2
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Jeff Hudson
08/15/2025, 3:23 PMDo you have the CORS plugin installed?
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S.
08/15/2025, 3:24 PMyep, I'll send it in a bit. trying if it's missing the user agent header now which is also sent during preflights
j
Jeff Hudson
08/15/2025, 3:25 PMPreflight OPTIONS requests are part of the CORS browser security feature, so Ktor only auto-handles them when that plugin is installed.
Jeff Hudson
08/15/2025, 3:25 PMNot whitelisting a particular header sounds like a likely cause though!
(for anyone reading this later) With the CORS plugin you need to explicitly specify which headers are allowed.
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S.
08/15/2025, 3:27 PMyeah sorry, CORS plugin is applied ofc
S.
08/15/2025, 3:30 PMit was indeed that
allowHeader(HttpHeaders.UserAgent)j
Jeff Hudson
08/15/2025, 3:30 PMAmazing, glad you figured it out!
s
S.
08/15/2025, 3:31 PMluckily I stumbled upon this https://youtrack.jetbrains.com/issue/KTOR-6458/UserAgent-plugin-sends-the-header-even-when-Access-Control-Allow-Headers-doesnt-allow-it
don't think I would have found the issue anytime soon otherwise
S.
08/15/2025, 3:37 PMand what still throws me off is the fact that only safari and firefox respect the custom user agent, chrome still sends it's own
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