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Showing content from https://devcenter.heroku.com/articles/custom-domains below:

Custom Domain Names for Apps

• Heroku Architecture
• Networking & DNS
• Custom Domain Names for Apps

Last updated March 13, 2025

By default, a Heroku app is available at its Heroku domain, which has the form APPNAME-IDENTIFIER.herokuapp.com or APPNAME-IDENTIFIER.DNS-ZONE.herokuapp.com. For example, an app named example-app is hosted at example-app-1234567890ab.herokuapp.com. While your app is available at your subdomain, we strongly recommend adding a custom domain to production apps.

Heroku started appending identifiers to subdomains on June 14, 2023. Applications created before this date follow the old subdomain scheme where the subdomain was the same as the app name.

Heroku DNS uses DNSSEC to authenticate requests to all herokuapp.com and herokudns.com domains. DNSSEC is a security system that gives DNS servers the ability to verify that the information they receive is reliable.

To make your app available at a non-Heroku domain (for example, www.yourcustomdomain.com), you add a custom domain to it.

You can add custom domains to any Heroku app. Adding domains does not incur extra charges. For security purposes, you must verify your Heroku account to add domains to apps.

Heroku does not provide a domain registration service (for registering a custom domain name) or a DNS provider service (for hosting the DNS servers that point your custom domain name to your app).

The remainder of this article covers these steps in greater detail:

1. Confirm that you own the custom domain name. You can buy a custom domain name with a domain registration service.
2. Add the custom domain to your app with the heroku domains:add command.
3. Look up the Heroku-supplied DNS target for the custom domain using the heroku domains command.
4. Configure your app’s DNS provider to point to the Heroku-supplied DNS target.
5. Confirm that your app is accessible via the custom domain. There might be a delay while DNS changes propagate.

To add a custom domain with a subdomain, use the domains:add Heroku CLI command:

$ heroku domains:add www.example.com -a example-app
Adding www.example.com to ⬢ example-app... done
 ▸    Configure your app's DNS provider to point to the DNS Target
 ▸    whispering-willow-5678.herokudns.com.
 ▸    For help, see https://devcenter.heroku.com/articles/custom-domains

The domain www.example.com has been enqueued for addition
 ▸    Run heroku domains:wait 'www.example.com' to wait for completion

Domain names that contain accented, or other non-ASCII, characters should be added using punycode. For instance, the éste.com domain name should be first converted to xn--ste-9la.com

See the Rules on adding domains section if you receive the error message example.com is currently in use by another app.

After you add a domain with the heroku domains:add command, you need to point your DNS provider at the DNS target provided by Heroku. You can view this DNS target with the heroku domains command. See View existing domains for details.

You usually configure a new CNAME record with your DNS provider to point it at Heroku. The following table shows common CNAME record patterns:

The trailing . on the target domain may or may not be required, depending on your DNS provider.

Consult your DNS provider’s documentation for specific instructions on creating CNAME records.

You can confirm that your DNS is configured correctly with the host command, assuming your DNS changes have propagated:

$ host www.example.com
www.example.com is an alias for whispering-willow-5678.herokudns.com.
...

DNS changes can take between several minutes and several days to take effect. Lowering your DNS TTL ahead of time can minimize, but not eliminate, this propagation time.

Your app’s Heroku domain always remains active, even if you set up a custom domain. If you want users to use the custom domain exclusively, your app should send HTTP status 301 Moved Permanently to tell web browsers to use the custom domain. The Host HTTP request header field shows which domain the user is trying to access; send a redirect if that field is example.herokuapp.com.

Keep in mind that you have to maintain your DNS records in sync with your Heroku resources. If you decide to remove a Heroku app but do not remove or update your corresponding DNS record, you become vulnerable to Subdomain Takeover attacks.

Root domains must be added in addition to any subdomains. The process for adding root domains is the same in the Heroku CLI:

$ heroku domains:add example.com -a example-app
Adding example.com to ⬢ example-app... done
 ▸    Configure your app's DNS provider to point to the DNS Target
 ▸    whispering-willow-5678.herokudns.com.
 ▸    For help, see https://devcenter.heroku.com/articles/custom-domains

The domain example.com has been enqueued for addition
 ▸    Run heroku domains:wait 'example.com' to wait for completion

Configuring your DNS provider for a root domain is similar to configuring a DNS provider for a subdomain. However, whereas with subdomains the type of record to configure is always a CNAME, with root domains the type of record depends on the DNS provider:

• ALIAS at DNSimple
• ANAME at DNS Made Easy
• ANAME at easyDNS
• ALIAS at PointDNS
• CNAME at Cloudflare. Also see the document Configure Cloudflare and Heroku over HTTPS.
• ALIAS at Namecheap
• ALIAS at DreamHost

Some DNS providers only offer A records for root domains. Unfortunately, A records aren’t sufficient for pointing your root domains to Heroku because they require a static IP. These records have serious availability implications when used in environments such as on-premise data-centers, cloud infrastructure services, and platforms like Heroku. Because Heroku uses dynamic IP addresses, it’s necessary to use a CNAME-like record (often referred to as ALIAS or ANAME records) so that you can point your root domain to another domain. See examples below.

Whichever provider you have, point the ALIAS/ANAME/CNAME entry for your root domain to the DNS Target, just as you would with a CNAME record:

Depending on the DNS provider, an empty or @ Name value identifies the root domain.

Wildcard domains allow you to map any and all subdomains to your app with a single record. A common use of a wildcard domain is with applications that use a personalized subdomain for each user or account. You can add a wildcard domain if you own all existing apps already using the same top-level domain (TLD). For example, if an app is already using www.example.com, you must own it to add *.example.com.

Add a wildcard domain to your app as you would with any other domain, but use the * wildcard subdomain notation.

$ heroku domains:add *.example.com -a example-app
Adding *.example.com to ⬢ example-app... done
 ▸    Configure your app's DNS provider to point to the DNS Target
 ▸   encircled-magnolia-9265.herokudns.com.
 ▸    For help, see https://devcenter.heroku.com/articles/custom-domains

The domain *.example.com has been enqueued for addition
 ▸    Run heroku domains:wait '*.example.com' to wait for completion

If one of your apps has a wildcard domain, you can still add specific subdomains of the same top-level domain (TLD) to any of your other apps. Specific subdomains are evaluated before wildcard domains when routing requests.

With wildcard domains it’s important to make sure your DNS provider configuration agrees with Heroku. In particular, if you have configured your DNS for *.example.com to point to example.herokuapp.com, be sure you also run heroku domains:add *.example.com. Otherwise, a malicious person could add baddomain.example.com to their Heroku app and receive traffic intended for your application.

Use the * wildcard subdomain notation to add a CNAME record to encircled-magnolia-9265.herokudns.com. with your DNS provider.

Remove a domain with domains:remove:

$ heroku domains:remove www.example.com -a example-app
Removing www.example.com from ⬢ example-app... done

If you destroy the app, any custom domains assigned to it gets freed. You can subsequently assign them to other apps.

Use the heroku domains command to view an app’s current Heroku domain, custom domains, and DNS targets:

$ heroku domains -a example-app
=== example Heroku Domain
example.herokuapp.com

=== example Custom Domains
Domain Name      DNS Target
---------------  --------------------------
example.com      hidden-sierra-7936.herokudns.com
www.example.com  whispering-willow-5678.herokudns.com

Common Runtime

For older applications, the DNS Target may be of the form [name of app].herokuapp.com. If you’re not using TLS, both [name of app].herokuapp.com and <haiku>.herokudns.com formats work as DNS Targets, regardless of the DNS Targets shown in Dashboard and CLI output.

We recommend using the <haiku>.herokudns.com format as this format is required when uploading your own certificate or using Automated Certificate Management.

Cedar and Fir Private Spaces

The DNS Target format for Private Space apps depends on its generation. Cedar Private Spaces use <haiku>.<haiku>.herokuspace.com. Fir Private Spaces use <haiku>.<regional-haiku>.herokudns.com.

Any Heroku user can attempt to add any domain to their app. Instead of explicitly verifying domain ownership, Heroku enforces the following rules to ensure that domains aren’t claimed by multiple users or apps:

• A single app can have up to 1,000 custom domains assigned to it.
• A given domain can be added to only a single Heroku app. For example, if you add www.example.com to app example-1, you can’t also add it to app example-2.
• You can add a wildcard domain if you own all existing apps that already use a corresponding subdomain. For example, if an app is already using www.example.com, you must own it in order to add *.example.com.
• You can add a subdomain or apex domain if you own the app that is assigned the corresponding wildcard domain. For example, to add www.example.com or example.com, you must own the app with *.example.com (if such a custom domain exists).
• You can add a subdomain if all applications using wildcard TLS certificates for that domain are owned by the same account. For example, if another account has an app with a *.example.com wildcard TLS certificate uploaded, you can’t add something.example.com to an app on your account.
• wildcard is a reserved Heroku subdomain keyword. For example, wildcard.example.com fails.

If you’re unable to add a domain that you own, please file a support ticket.

• Domain or domain name: full name used to access an app (in words, not with an IP address). For example, www.yourcustomdomain.com
• Subdomain: the www in www.yourcustomdomain.com
• Root domain (or naked, bare, or zone apex domain): the ‘yourcustomdomain.com’ in ‘www.yourcustomdomain.com’
• Wildcard domain: domains that match any subdomain, represented as *.yourcustomdomain.com
• Domain registration service: company that lets you buy and register a custom domain name
• DNS provider: company that maintains the DNS servers that translate a custom domain name to a destination (‘DNS Target’). The fields are often called CNAME, ALIAS, ANAME, or A records. Only the first three work with Heroku apps, as A records require an IP address and Heroku apps do not have stable inbound IP addresses.
• Heroku Domain: Heroku term for default domain given to each app. Has the form APPNAME-IDENTIFIER.herokuapp.com.
• DNS target: Heroku term for the Heroku domain to give to a DNS provider (e.g., in a CNAME record) to be the destination for a custom domain name.

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