Vercel custom IDN domain returns HTTP 200 but response body stalls during download

(edited)

Hi everyone,

I have a static site deployed on Vercel that works correctly on the project domain but hangs on my custom IDN domain.

Affected Domains

Working domain:
https://greenhouse-eosin.vercel.app/ — full page loads normally

Affected domain:
https://www.xn–90ahalobcoje5a6c9c.xn–p1ai/ — browser shows infinite loading

Issue Details

No redirect loop
Response starts with HTTP 200 OK
Body download stalls at ~21,085 bytes (out of 154,162 total)
Same deployment and content load fully on the .vercel.app domain

What I've Tried

Re-added both domains (www and apex) in project settings
Set www as primary, apex as redirect
DNS is delegated to Vercel nameservers
Cleared local DNS and browser caches
Tested in multiple browsers
Verified with curl — custom domain stalls, .vercel.app completes

My Guess

Something in edge routing / CDN path / TLS handling specific to IDN domains.

Has anyone experienced similar issues with IDN (punycode) domains? Any suggestions appreciated!

Hi mate! I tested both domains and couldn’t reproduce a global issue, both return 200 and load the full ~154 KB HTML with identical content, so this doesn’t look like a deployment or DNS problem.

Given your symptom (stalling around ~21 KB), this points to a region / edge / protocol-specific issue (likely a Vercel POP or HTTP/2/HTTP/3 behavior affecting the IDN hostname).

Things that would help confirm:

Force HTTP/1.1 vs HTTP/2 with curl
Test from another network (mobile/VPN)
Share a failing x-vercel-id

If it only happens in certain networks/regions, Vercel can trace it to a specific edge node.

I think your setup looks correct, this is very likely on the edge delivery side. hope this helps

Hi team hope this helps!

Behavior

200 OK returned
Response stalls at ~21 KB (expected ~154 KB)
No redirect loop
Reproducible by user (browser + curl)
.vercel.app works normally

Verification

When successful, both domains return identical content (same size, hash, headers)
Range requests work
DNS and deployment appear correct
Issue not globally reproducible

Interpretation

Likely edge-specific issue (region/POP/protocol), possibly:

HTTP/2 or HTTP/3 handling
cache inconsistency across edge nodes
punycode hostname routing/SNI differences

Helpful debugging data

Failing x-vercel-id
HAR file
Affected region/ISP
Whether HTTP/1.1 avoids the issue

Conclusion: not a project/config issue; likely isolated to specific edge nodes serving the custom IDN hostname.

Vercel Alum

Seems to be working now, I tried connecting from the UK. Are you still seeing this?

reply to #6

1) x-vercel-id

arn1::5595f-1775209274782-579dda772cfd

In chrome was used http2 , after chrome.exe --disable-http2 --disable-quic site partly loaded

Cant added har file because of type of file even txt ( https://docs.google.com/document/d/1I7gQNrt-1fn3LaSrh5PjuXo53Fypwaf9DyUK91JTATI/edit?tab=t.0 )
Region and provider: St. Petersburg, Rostelecom
It’s depended on region https://g-i-t.ru/domains/site-availability/?domain=xn--90ahalobcoje5a6c9c.xn--p1ai

reply to #7

I located in Russia and still have problem(