Error 520 and Error 521 are Cloudflare-specific errors that indicate an issue between Cloudflare and the website’s server. There are a number of possible causes, so there are troubleshooting steps that need to be followed to track down the source.

What’s Causing the Error?

Error 520 indicates Cloudflare received an empty, unknown, or unexpected response from the server. Error 521 indicates that the server refused a connection with Cloudflare.

If you see either of these errors on a site hosted at Kinsta, check out the information below to see the next steps to resolve this issue.

Site Visitor

If you see one of these errors while visiting a site, but you aren’t the site owner or administrator, we recommend contacting the site owner so they can resolve the issue.

Be sure to include a screenshot of the error or at least the Cloudflare Ray ID that is shown below the error.

Site Owner or Administrator Non-Cloudflare Domain

If you’re the site owner or administrator and do not have your own Cloudflare account, open a new chat with our Support team. The following information isn’t required but can be helpful as we look into the issue:

  1. The date and time the error occurred.
  2. The Cloudflare Ray ID shown under the error message.
  3. Any steps you or your visitor were taking when the error occurred (e.g. clicking on a link, updating content, adding something to a cart, submitting a form, or other action).

Site Owner or Administrator Cloudflare Domain

If you’re the site owner or administrator and have your own Cloudflare account, check out our detailed guides for resolving each of these errors: