Challenge Request 429: the most common Let’s Encrypt error is also the easiest to avoid

Let’s Encrypt has an hourly limit of 5 validation failures per hostname.

If you’re not careful, you can get a “LetsEncrypt challenge request 429” error. Once you trigger the hourly limit, there’s nothing to do but wait!

Challenge Request 429: the most common Let’s Encrypt error is also the easiest to avoid

Let’s Encrypt needs to validate that the domain points to the server trying to obtain the certificate – if this validation step fails repeatedly, it will trigger a 429 error.

Thankfully, there are some simple steps you can take to avoid this:

  1. Ensure that your domain name is resolving correctly to your server.
    • If you recently made changes to your nameservers and/or DNS entries, these changes might not have yet propagated.
    • To verify that the DNS entry for your domain has propagated correctly, you can use a free service such as DNSMap.
  2. If your domain is not resolving to your server’s IP or hostname, you should double-check your DNS entries.
  3. If you are trying to obtain a certificate for a sub-domain, ensure that it is set-up correctly.
  4. Finally, and this goes without saying: make sure you understand what’s going on before blinding making many tentatives.

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Samuel Hautcoeur
Co-Founder of WP Captain, I have more than a decade of WordPress and server management experience. Currently leading product development and server architecture.

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