Error 521 since 2 week

Hi community cloudflare , i am facing big problem since two weeks :frowning: .
I have upgrade my hosting plan and When i activate cloudflare on my websites (, i got error 521 and when i stop cloudflare website work fine .
I have contacted namecheap support and after 2 hours of assistance they told me to contact you and provide link to this thread to help your support to solve my situation : 521 Even though web server is fine Second , they and i , we are pretty sure that these common causes are properlly checked :

  • changing ip adressess in dns section : done
    Ensure your origin web server is responsive
    Review origin web server error logs to identify web server application crashes or outages. Confirm Cloudflare IP addresses are not blocked or rate limited Whitelist all Cloudflare IP ranges in your origin web server’s firewall or other security software
    Please help me to fix my issue as i told you before i have more then 2 weeks facing this issue
    All helps are appreciated.
    Thank you for your coorporation.

@sdayman i have been forced to repost my topic , where can i find railgun ? And how to disactivate it ?

@hadjkacemohamed Railgun is under Speed -> Optimization then down to railgun. Though I doubt it would cause 521 errors.

Are you able to contact the website directly by IP? And what do the logs of your website show? Are there connections being made then failing or is it not connecting at all?

1 Like

@Cyb3r-Jak3 thank you for your reply :
1- i have disabled railgun and it seems to be fine there is no error until now but as you can see in this screenshot connection isn’t secured

How to fix this please ? Any suggestion .!

2- i have charged namecheap support to take care of cheking connection , config , blacklisting cloudflare ips … and told me that every thing good.

Thank you for your help community cloudflare

@hadjkacemohamed It works fine for me now. I would suggest clearing your cache and loading it again.

Hi @Cyb3r-Jak3,

I had a similar issue a couple of days ago, where railgun caused a 521 error on my website.

SiteGround helped me identify the problem, and once they disabled railgun everything worked again.

There was nothing intentionally changed or updated through the site.


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