DNS Record Crash Course for Web Developers

Chris Achard on October 29, 2019

This was originally posted as a twitter thread: https://twitter.com/chrisachard/status/1188870256971915265 Confused by DNS Records? A, CNAME, ALIA... [Read Full]
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Chris, awesome post, straight to the point. 🙌🏼

Can I suggest an edit?
It would be great, by using different colors, or just pointing it out, what is shown in your browser, and what is served.

E.G if I use a CNAME (does C stand for Canonical? 🤔) redirecting www.example.com to example.com, you can make it clearer with colors that the host www typed into the address bar will be shown in place of the domain without it, which, in turn, will show the actual content on the server.

TYPE            HOST    URL (in browser)         DOMAIN (served)
A Record        @       example.com        ->
CNAME Record    www     www.example.com    ->    example.com
CNAME Record    blog    blog.example.com   ->    example.herokudns.com

That way, it's easier to understand that:

URL IN BROWSER                                ACTUAL CONTENT SERVED
www.example.com    ->    example.com    ->

And, again, thanks for the super useful wrap-up!


This is a great way to visualize/explain it. Thanks!


Hi Chris, i recently finished developing my portfolio using Angular8, and then yesterday i did register for a domain with netlify which costed about $16.99
after registration it did gave me those option to setup the A , CNAME, AAA records but i was still busy with some functionality of my portfolio. So i'd just brushed it off that i will do all that set up once i am done fixing the error on the IDE. So now i've deployed my site, the site is live but got an error when i clicked on its link' error : "Page not found, Looks like you've followed a broken link or entered a URL that doesn't exist on this site. " '

I have reached to out to support, its been almost 5 hours without any response


Maybe a post in the help tag could help get you to the bottom of this?


A place to ask questions and provide answers. We're here to work things out together.

Hm; I haven't actually bought a domain through netlify before (I buy them outside of netlify and setup DNS separately), so I'm not 100% sure what might be happening, but I have a few ideas:

  1. Can you access the site directly with the "your-app.netlify.com" address? (if not, then it's not deployed correctly, so changing DNS stuff won't do anything)

  2. Can you access the domain part of netlify and check to see if the domain is "Verified"? (it turns green with no warning symbol)

  3. If the dns records are there and the site is working directly, it's possible it's a DNS cache issue - though 5 hours is usually enough in my experience for it to clear and fix itself, so that doesn't sound like it...

Does that help at all?


The thing is i developed the site using vscode and then push my commits to its repo on github, and i fetched from github to netlify. Which deployed without any error. "My-app.netflify.com" is the one that's giving me the "Page Not Found Looks like you've followed a broken link or entered a URL that doesn't exist on this site." error and when i used my registered domain it want to DNS configuration. " to set up https. It's rollcoaster ride to be honest/

ah, if the direct netlify link doesn't work, then it's not a DNS issue - something went wrong with deploying your site. Under "deploys", make sure there is at least one successful build, and then click that link directly to see if it's working.

Hope you can figure it out! (sorry, can't help much if it's a deploy issue... keep trying/waiting for netlify support I suppose).


Hi Chris,

Thanks for this. Actually for #5 you can do this at root level without breaking DNS specification dates from 1987. Cloudflare introduced CNAME Flattening feature, very useful if you’ve looking for a way to make your root domain work on a hosted service like AWS and Heroku.


Is that what they call a "virtual" CNAME, or something else? I think I read about that, but thought it was a different option (on Cloudflare) than just a normal CNAME? (could be wrong though - I haven't setup Cloudflare before)


Thanks for this article, I didn't know about the CNAME limitation and the use of ALIAS to solve the problem. Good post Chris 🥂


Just ensure that your DNS provider supports ALIAS as a resource record type, as it isn't defined by the official RFCs which govern the behaviour of the DNS.


Yes, definitely - different DNS providers have different workarounds.


Amazing thanks. DNS has always been a pretty mysterious topic for me, so this was very helpful!


This is really interesting! Thanks for sharing. I think a cool follow up post might be digging into the history of DNS and why it was created in this fashion.

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