HTTP 520 Errors

Thanks @domjh for the quick reply.

I can confirm all of our internal load balancers show normal metrics (e.g. under 50ms latency) and no http 500s recorded in our load balancers.

We can access the same site without Cloudflare (only for testing purposes) and no http 520 is observed.

No problem!

Can you please check that you have whitelisted the Cloudflare IPs as in step 3 of the linked guide?

All Cloudflare ip addresses have been white listed (we have had this setting for 1.5 years now). we also checked if there has been any changes to the ip list from Cloudflare and there is none (ipv4 and v6).


Great, can you just confirm with the dev tools in your browser that with Cloudflare paused on the site, it returns a 200 status code?

I can confirm we get http 200s when we bypass Cloudflare (e.g. accessing via the load balancer DNS directly). all requests are served with normal speed. (the home page of the website makes 100+ API calls)

I will test making changes to Cloudflare setting (e.g. pause) in the next 2 hours (once our DevOps is online).

Are you aware of any widespread issues with Cloudflare across any specific regions ? if not then this is probably specific to our site and perhaps some Cloudflare setting.


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Nope, I don’t have any more specific info than at the moment which shows no issues.

I would suggest you contact Cloudflare Customer Support (click the ‘Get more help’ option) and provide example URL(s) and Ray ID and output from a traceroute from any impacted user, copy the output of . Also include two HAR file(s) : one detailing your request with Cloudflare enabled on your website and the other with Cloudflare temporarily disabled - see How do I temporarily deactivate Cloudflare ? These HAR files will be helpful in comparing server responses.

You can link to this thread in your message as well and post the ticket number you get here so the mods can keep an eye. Another forum user may also have other suggestions :slight_smile:

ok. thank you for your help.

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No problem, hope you manage to get it resolved soon :slightly_smiling_face:

this is strange but the issue has been resolved now (we observed issues for around 4 hours). we no longer get http 520 or http 502 (it started with 502 then it became 520).

I’m fairly confident there has been no changes in our end and stuff we have tested so far only indicated issues at Cloudflare level.


That is odd, Community Tip - Fixing Error 502 / 504: Bad Gateway is the info on the 502 you mentioned.

I would suggest you still contact support and ask, providing any info such as connection IDs as you can as they should be able to look into it and provide more info/help with what could have caused this. Not seen anything indicating an issue with Cloudflare at the moment or earlier…

Sorry I can’t be of more help!

I’m having same problem, my site is show me Erro 520 all time…
My hosting said that’s problem is about you…

Hi @passocurto, Have a read of Community Tip - Fixing Error 520: Web server is returning an unknown error.

They often do and it quite often is not :wink:

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We are experiencing this with BlueHost and after all the same tests above they conclude that it is Cloudflare that is at fault. We have bypassed the firewall, cleared the cache and still getting 520 errors. Interestingly enough the server is not recording any off the 500 errors which led us to find this post. If you guys find a solution quickly please let us know.

How often are you getting the 520 errors?

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Just click on a few links and it is about 1/7 page clicks.

That sounds like rate limiting. Can you post a URL this is happening on?
Click on a few links and it is going to happen again.

Just got:
Error 525 Ray ID: 4f6d28182a9a58dd • 2019-07-15 16:36:42 UTC

SSL handshake failed

If I remove Cloudflare everything works perfectly.

I can’t replicate the issue. The site has ~10 pages, and I’ve visited them all twice in rapid succession and never got any 5xx errors. A 525 is very different from a 520, but neither happened for me.

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It looks like it has been resolved. We are going strong again. It was interesting that it only failed when Cloudflare was on.

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