# Cloudflare HTTP 525

**URL:** <https://community.fly.io/t/cloudflare-http-525/26311>\
**Category:** General\
**Tags:** certificates, proxy, login-only\
**Created:** [October 26, 2025, 8:35am UTC](https://community.fly.io/t/cloudflare-http-525/26311 "2025-10-26T08:35:32Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![fnowacki](https://sea1.discourse-cdn.com/fly1/user_avatar/community.fly.io/fnowacki/32/44261_2.png) [@fnowacki](https://community.fly.io/u/fnowacki)\
**Post date:** [October 26, 2025, 8:35am UTC](https://community.fly.io/t/cloudflare-http-525/26311/1 "2025-10-26T08:35:32Z")

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Hey! I’ll admit that I’ve already tried everything and I’m about to give up… I’ve had applications configured on [fly.io](http://fly.io) with a Cloudflare proxy for several months in the following way: Cloudflare proxied (orange cloud) with AAAA records ipv6; strict mode: full No certificate on the [fly.io](http://fly.io) side

Generally, I followed the instructions from the documentation: [https://fly.io/docs/networking/understanding-cloudflare/#cdn-proxy-setup-quot-orange-cloud-quot](https://fly.io/docs/networking/understanding-cloudflare/#cdn-proxy-setup-quot-orange-cloud-quot)

I have several applications running this way:  
app-a → [domain.com](http://domain.com)  
app-b → [b.domain.com](http://b.domain.com)  
app-c → [c.domain.com](http://c.domain.com)  
app-d → [d.domain.com](http://d.domain.com)

Sometimes it happens that I get HTTP 525, but after a few minutes everything returns to normal. Unfortunately, since yesterday afternoon for app-b, I’ve been constantly getting HTTP 525. All applications are configured in exactly the same way as I described above (ipv6, aaaa record, no certificate on the [fly.io](http://fly.io) side).

Where else can I look for the cause?

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**Author:** ![bglw](https://sea1.discourse-cdn.com/fly1/user_avatar/community.fly.io/bglw/32/51112_2.png) [@bglw](https://community.fly.io/u/bglw)\
**Post date:** [October 26, 2025, 11:15pm UTC](https://community.fly.io/t/cloudflare-http-525/26311/2 "2025-10-26T23:15:47Z")

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Hi!

> strict mode: full No certificate on the [fly.io](http://fly.io/) side

Interesting, I would _not_ expect this to have been functional. For a [Fly.io](http://Fly.io) app behind Cloudflare you should still be adding a certificate (either in the dashboard or via the CLI with `fly certs add`).

Can you try adding that certificate to your app? If you have AAAA records in Cloudflare, and no A records, then this should generate the certificate automatically within a couple of minutes.

The several month timeframe might also be a good clue. Did you have an app certificate configured at some point in the past? If so, the latest certificate will have been served until its expiry (90 days).

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**Author:** ![system](https://global.discourse-cdn.com/fly1/original/3X/6/e/6e8955d00cb218e186ebbe3a6ab06fefdce15290.svg) [@system](https://community.fly.io/u/system)\
**Post date:** [November 2, 2025, 11:16pm UTC](https://community.fly.io/t/cloudflare-http-525/26311/3 "2025-11-02T23:16:35Z")

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