Hey there! Are you getting the CloudFront 421 error? This error can be a real pain but don’t worry, I’m here to help. In this tech-savvy article, I’ll explain what the CloudFront 421 error is, why it happens, and how to fix it.
Amazon CloudFront is a content delivery network (CDN) service. It’s super fast and reliable, making sure your data, videos, apps, and APIs reach customers around the world in a flash. Plus, it plays nicely with other Amazon services, so setting up and managing your web content delivery is a breeze.
Now, I know you’re itching to get rid of the CloudFront 421 error and get back on track. Keep reading to discover what the CloudFront 421 error is, why it happens, and how to troubleshoot and conquer this error once and for all.
In This Article
What CloudFront 421 Error?

The CloudFront 421 error is a type of error that can pop up when you’re trying to visit a website that uses Amazon CloudFront. You know, CloudFront is a fancy service that helps websites load faster and safer. So, this error means that something didn’t go as planned when CloudFront tried to connect to the website’s server.
Basically, when you visit a website, your browser sends a request to CloudFront, which then talks to the website’s server. The server is supposed to respond with the stuff you want to see, like web pages, images, or videos. But sometimes, CloudFront and the server get a bit confused about the domain or subdomain names they’re using. So, let’s say you want to visit www.example.com, but the server thinks you’re trying to see blog.example.com. That confuses CloudFront, and it sends you that CloudFront 421 error.
In simpler terms, the CloudFront 421 error means that there’s a mix-up between CloudFront and the website’s server. They’re not on the same page about the domain names, and that’s why you’re seeing that error message. But don’t worry; it’s usually a quick fix once you figure out what’s going on.
Why Does CloudFront 421 Occur?

Alright, let’s break down the reasons why that CloudFront 421 error can be a party pooper. Here are some of the most common causes that can make this error show up:
01. Messed-up Domain Name: Sometimes, the domain name isn’t set up correctly. It’s like CloudFront, and the server can’t agree on the right name to use. It’s like calling someone by the wrong name at a party. Awkward!
02. Certificate Confusion or Clash: Sometimes, the website uses one SSL/TLS certificate for multiple domains or subdomains. But here’s the twist: CloudFront only recognizes one of them. It’s like having a VIP list at a party, but CloudFront doesn’t recognize all the cool guests.
03. Expired or Invalid Certificates: If the website’s SSL/TLS certificate has expired or is invalid, it’s like trying to get into a party with a fake ID. CloudFront won’t trust it, and you’ll be left outside in the cold.
04. Outdated Browser Blues: Using an outdated browser is like showing up at a party in last year’s fashion trend. It might not vibe well with CloudFront, leading to the CloudFront 421 error.
05. Proxy Problems: If the client is using a proxy server that’s not properly set up, it’s like trying to navigate through a maze at a party. It can lead to some serious head-scratching moments.
How to Fix CloudFront 421 Error?

Once you’ve identified the cause of the CloudFront 421 error, you can usually fix it pretty easily. Here are some of the most common fixes:
01. Check the domain name configuration: Double-check the settings to ensure they match with CloudFront. If there’s a mismatch, fix it to align with the domain you’re trying to access.
02. Verify the SSL certificate: Confirm that the certificate is valid and trusted by CloudFront. If there are any issues or conflicts, consider obtaining a new or updated certificate from a trusted certification authority.
03. Configure the proxy server correctly: Ensure that the proxy server settings are properly configured to work seamlessly with CloudFront. Incorrect configurations can lead to disruptions in the connection, so make sure everything is set up correctly.
04. Update your browser: Keep your browser up to date with the latest version. Updates often include bug fixes and security enhancements that can resolve compatibility issues with CloudFront.
05. Clear your browser cache and cookies: Sometimes, cached data or stored cookies can interfere with the connection to CloudFront. Clearing them can help refresh the browser and eliminate any potential conflicts.
06. Contact your web hosting provider or CDN service provider: If the issue persists, reach out to the experts. They can provide specialized assistance, troubleshoot the problem, and ensure that all configurations and settings are optimized for CloudFront’s smooth functioning.
How to Prevent CloudFront 421 Error?

The best way to deal with the CloudFront 421 error is to prevent it from happening in the first place. Here are some tips:
01. Use a dedicated SSL/TLS certificate for each domain name or subdomain name that you want to serve through CloudFront. This will help to ensure that your website and CloudFront are working together properly. You can use AWS Certificate Manager (ACM) to request, manage, and renew your SSL/TLS certificates for free.
02. Use a valid SSL/TLS certificate. Make sure that your SSL/TLS certificate is not expired or invalid, and that it matches the domain name or subdomain name that you are using. You should also make sure that your SSL/TLS certificate is trusted by CloudFront and your browser.
03. Configure your proxy server correctly. If you are using a proxy server to connect to CloudFront, make sure that it is configured correctly and that it does not interfere with the SSL/TLS handshake or the HTTP requests. You should also make sure that your proxy server supports the HTTP/2 protocol, which is used by CloudFront.
04. Use a modern browser. Make sure that you are using a browser that supports HTTP/2 protocol and SNI (Server Name Indication), which are used by CloudFront to identify the correct domain name or subdomain name. You should also update your browser regularly to avoid any bugs or security issues.
By following these tips, you can help to prevent the Amazon CloudFront 421 error from happening and keep your website running smoothly.
Wrapping Up
Alright, folks, that is a wrap! I hope this article has helped you figure out what the CloudFront 421 error is, why it happens, and how to fix and prevent it. Got any burning questions or thoughts to share? Drop ’em in the comments below, and I will be all ears!
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Frequently Asked Questions
01. What is the CloudFront 421 error?
The CloudFront 421 error is a client error that occurs when the client tries to connect to a CloudFront distribution but the request is redirected to a different domain.
02. Why does the CloudFront 421 error occur?
The CloudFront 421 error can occur for a few reasons, such as if the domain name is not configured correctly, there is a conflict with the SSL certificate, or the client is using a proxy server that is not configured correctly.
03. What is a dedicated SSL/TLS certificate?
A dedicated SSL/TLS certificate is a certificate that is specifically designed for a particular domain name or subdomain name. This helps to ensure that the certificate is trusted by CloudFront and your browser.
04. What is a proxy server?
A proxy server is a server that acts as an intermediary between your computer and the website you are trying to access. This can be helpful for improving performance or security.
05. What is SNI?
SNI stands for Server Name Indication. It is a feature that allows a client to specify the domain name or subdomain name that it is connecting to when it makes an HTTP request. This helps to prevent the CloudFront 421 error from occurring.