Offload CORS to Front Door

Question

Offload CORS to Front Door

Daniel Matthews 25

Hi,

According to the documentation (https://learn.microsoft.com/en-us/azure/frontdoor/standard-premium/troubleshoot-cross-origin-resources) it is possible to configure a rule to manage CORS origins.

However, it appears that Front Door can not respond to preflight requests itself without routing to the origin. The rule described in the documentation merely decorates a response with CORS headers. This defeats the point of off-loading it to the edge, as I still have to handle it on the backend.

Am I misunderstanding this or is there any other way for AFD to handle this?

Accepted answer

0 additional answers

Your answer

Answer 1

Daniel Matthews hi,

thanks for dropping this question, its a good one and i get why u're scratching ur head over it )

u're actually spot on about how azure front door handles cors right now. the rule engine can add cors headers to responses, but it won't fully intercept preflight options requests. those still get passed through to ur origin server. kinda annoying, right?

for the full cors offload dream, u'd need something that can respond to options requests at the edge. azure front door isn't quite there yet, but there are ways to make it work better ))

check this microsoft doc that explains the current behavior https://learn.microsoft.com/en-us/azure/frontdoor/standard-premium/troubleshoot-cross-origin-resources. it shows how to set up those response header rules properly.

if u're using azure app service or azure functions, u could set up a lightweight cors handler there that just responds to options. not perfect, but better than handling full cors logic.

also worth looking into azure api management - it has more robust cors handling features that might do what u need. its not front door, but could be part of ur solution ))

if u're using cloudflare or another cdn in front of front door, some of them handle cors better. just saying )

let me know if this helps

Alex

and "yes" if you would follow me at Q&A - personaly thx.
P.S. If my answer help to you, please Accept my answer

https://ctrlaltdel.blog/

Daniel Matthews 25 Reputation points

2025-08-06T09:47:27.0233333+00:00

Thanks Alex,

That's a shame, and yes, it's kind of annoying :-(

Do you know if there is a features roadmap at all for AFD?
Alex Burlachenko 13,330 Reputation points Volunteer Moderator

2025-08-06T12:07:54.67+00:00

yw any time Daniel, unfortunately, microsoft doesn't always share detailed public roadmaps for azure services like front door. they tend to announce big features when they're ready to roll out. Try to check the azure updates page https://azure.microsoft.com/en-us/updates/ they post all new features there....

i feel u though - proper cors handling at the edge would be sweet. maybe ping ur microsoft rep if u have one? they sometimes share early info under nda.... but u know....

for now, u might wanna explore workarounds like super simple options handler on origin (just return 200 with headers), api management in front of backend (overkill but works), cloudflare workers if u can use another cdn...

keep an eye out tho - azure services update all the time. who knows, next month might bring that cors magic we want :))

ps - if u do hear any rumors about cors coming to front door, give me a shout yeah? %)

rgds,

Alex

Share via

Offload CORS to Front Door

0 additional answers

Your answer