Custom domains in Deno - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a custom domain in the context of web hosting?

A custom domain is a unique web address that you own and use instead of a default hosting provider's URL. It makes your website easier to find and remember.

intermediate

How do you link a custom domain to a Deno Deploy project?

You add your custom domain in the Deno Deploy dashboard and then update your domain's DNS settings to point to Deno's servers using CNAME or A records.

beginner

What DNS record types are commonly used to connect a custom domain to Deno Deploy?

CNAME records for subdomains (like www) and A records for root domains are commonly used to point your domain to Deno Deploy servers.

beginner

Why is HTTPS important when using a custom domain with Deno Deploy?

HTTPS secures the connection between users and your site. Deno Deploy automatically provides free SSL certificates for custom domains to keep data safe.

intermediate

What is a common troubleshooting step if your custom domain does not show your Deno Deploy site?

Check that your DNS records are correctly set and fully propagated. Also, verify that the domain is added and verified in the Deno Deploy dashboard.

Which DNS record type is typically used to point a subdomain like www to Deno Deploy?

A TXT

B CNAME

C MX

D NS

CNAME records map a subdomain to another domain, which is how www is usually pointed to Deno Deploy.

What must you do after adding a custom domain in Deno Deploy to make it work?

A Update your domain's DNS records

B Restart your computer

C Change your hosting provider

D Delete your project

You need to update DNS records so your domain points to Deno Deploy servers.

What does Deno Deploy provide automatically for custom domains?

A Database services

B Free domain registration

C Email hosting

D Free SSL certificates for HTTPS

Deno Deploy automatically issues SSL certificates to secure your custom domain with HTTPS.

If your custom domain is not showing your site, what is a good first step?

A Check DNS settings and propagation

B Change your domain name

C Uninstall Deno

D Clear your browser cache only

DNS settings must be correct and fully updated before your domain shows your site.

Which of these is NOT a benefit of using a custom domain?

A Easier to remember website address

B Improved website branding

C Automatic content creation

D More professional appearance

Custom domains do not create content automatically; they only provide a personalized web address.

Explain the steps to connect a custom domain to a Deno Deploy project.

Think about what you do in both Deno Deploy and your domain provider.

Why is it important to use HTTPS with your custom domain on Deno Deploy?

Consider what HTTPS does for websites in general.

Practice

1. What is the main purpose of setting a custom domain in a Deno server?

easy

A. To increase the server's processing speed

B. To use your own website name instead of a generic address

C. To automatically update the server software

D. To enable debugging features in Deno

Solution

1. Step 1: Understand what a custom domain is

   A custom domain lets you use a personalized website name instead of a default or generic address.

2. Step 2: Identify the purpose in Deno context

   Setting a custom domain in Deno allows your server to respond to your own website name, making it easier for users to find your site.

3. Final Answer:

   To use your own website name instead of a generic address -> Option B

4. Quick Check:

   Custom domain = personalized website name [OK]

Hint: Custom domain means your own website name, not generic [OK]

Common Mistakes:

• Confusing custom domain with server speed
• Thinking it updates software automatically
• Assuming it enables debugging

2. Which of the following is the correct way to set a custom domain hostname in Deno's serve function?

easy

A. serve({ url: "mydomain.com" })

B. serve({ domain: "mydomain.com" })

C. serve({ hostname: "mydomain.com" })

D. serve({ host: "mydomain.com" })

Solution

1. Step 1: Recall Deno serve options

   The serve function accepts an option called hostname to set the domain name.

2. Step 2: Match the correct option key

   Only hostname is the correct key; others like domain, host, or url are invalid here.

3. Final Answer:

   serve({ hostname: "mydomain.com" }) -> Option C

4. Quick Check:

   Use hostname option in serve [OK]

Hint: Use 'hostname' option exactly in serve function [OK]

Common Mistakes:

• Using 'domain' or 'host' instead of 'hostname'
• Passing the domain as a string without key
• Confusing 'url' with hostname option

3. Given the following code snippet, what will be the hostname the server listens on?

import { serve } from "https://deno.land/std/http/server.ts";
serve(() => new Response("Hello"), { hostname: "example.com" });

medium

A. The server will throw a runtime error

B. The server listens on localhost only

C. The server listens on all IP addresses

D. The server listens on example.com domain

Solution

1. Step 1: Examine the hostname option

   The code sets hostname: "example.com" in the serve options.

2. Step 2: Understand hostname resolution and binding

   Deno resolves "example.com" to a public IP (93.184.216.34) via DNS. If the IP is assigned to the local machine's network interfaces, the server binds successfully and listens on that domain. Otherwise, it will throw a runtime error.

3. Step 3: Typical behavior

   Usually, binding to a hostname that resolves to a public IP not assigned locally will fail. But if the environment is configured properly (e.g., hosts file or network interface), it can succeed.

4. Final Answer:

   The server listens on example.com domain -> Option D

5. Quick Check:

   Hostname option sets server listening domain [OK]

Hint: Hostname option sets server listening domain [OK]

Common Mistakes:

• Thinking server listens directly on domain without IP resolution
• Assuming default localhost behavior
• Believing it falls back to all IPs

4. You set hostname: "mydomain.com" in your Deno server but users cannot reach your site. What is the most likely cause?

medium

A. You forgot to point your domain's DNS to your server's IP address

B. The serve function does not support custom domains

C. You must use host instead of hostname

D. Deno requires a special flag to enable custom domains

Solution

1. Step 1: Verify Deno serve supports hostname

   Deno's serve supports hostname option, so options B, C, and D are incorrect.

2. Step 2: Check DNS setup

   If users cannot reach the site, the domain's DNS likely does not point to the server's IP, blocking access.

3. Final Answer:

   You forgot to point your domain's DNS to your server's IP address -> Option A

4. Quick Check:

   DNS must point domain to server IP [OK]

Hint: Check DNS points domain to server IP if unreachable [OK]

Common Mistakes:

• Assuming serve lacks custom domain support
• Using wrong option key like 'host'
• Thinking Deno needs special flags for domains

5. You want to serve your Deno app on your custom domain "myapp.com" and also allow access via localhost for testing. Which setup correctly supports both?

hard

A. Set hostname to "0.0.0.0" to listen on all interfaces including domain and localhost

B. Set hostname to "myapp.com, localhost" in a single serve call

C. Run two servers: one with hostname "myapp.com" and one with hostname "localhost"

D. Use hostname "localhost" and rely on DNS to redirect "myapp.com"

Solution

1. Step 1: Understand hostname options

   Setting hostname to "0.0.0.0" makes the server listen on all network interfaces, including your domain and localhost.

2. Step 2: Evaluate other options

   Run two servers: one with hostname "myapp.com" and one with hostname "localhost" requires two servers which is inefficient; Set hostname to "myapp.com, localhost" in a single serve call is invalid syntax; Use hostname "localhost" and rely on DNS to redirect "myapp.com" relies on DNS redirect which does not work for localhost access.

3. Final Answer:

   Set hostname to "0.0.0.0" to listen on all interfaces including domain and localhost -> Option A

4. Quick Check:

   Use 0.0.0.0 to listen on all interfaces [OK]

Hint: Use 0.0.0.0 hostname to serve domain and localhost [OK]

Common Mistakes:

• Trying to list multiple hostnames in one serve call
• Running multiple servers unnecessarily
• Relying on DNS to redirect localhost