Custom Domain DNS Records

The Custom Domain for your site requires you to configure specific DNS records for your domain. Configuring your DNS is a straightforward process, although the specific steps will vary depending upon your DNS provider.

CNAME Records

CNAME records are integral to your custom domain setup. CNAME records for your custom domain are not managed by Files.com, because they are for a domain that you control. You will need both administrator access to your Files.com site, as well as access to your account with the DNS provider for your domain to configure CNAME records.

Common DNS providers used by Files.com customers include Cloudflare, GoDaddy, NameCheap, Amazon Route 53, Hostinger, Microsoft Azure DNS, and Google Cloud DNS. As long as your DNS entries are resolvable by the public, they can be used with Files.com.

Configuring Your CNAME Record

Once you have chosen your custom domain, the next step is to set up a CNAME DNS record with your DNS provider. The CNAME record's value will depend on whether your custom domain will use an SSL certificate provided by Files.com or your own SSL certificate.

If you plan to use SSL certificates managed by Files.com, your CNAME record must point at your subdomain address. If you are using your own custom SSL certificate your CNAME will point to an address that contains your subdomain name in the form s-[subdomain].di.app.files.com.

We recommend using the shortest allowable TTL value for your CNAME record.

Recommended TTL Settings

We strongly recommend setting the TTL (Time to Live) for your custom domain CNAME records as low as permitted by your DNS provider, usually between 30 and 60 seconds. The DNS performance increase provided by large TTL values (many systems will default to 14400 seconds, or even 86400 seconds) is negligible compared to the risk of waiting hours or days for addresses to propagate. A short TTL minimizes the disruption when you change you the DNS record, such as when switching between your own SSL certificate and a Files.com-controlled certificate.

While you will encounter much higher recommendations elsewhere (even up to 24 hours) for the TTL of CNAME records, we believe that the negligible performance gains this offers are offset by the potential disruption. When you're making changes to the address used by your customers, employees and vendors to access your site, you don’t want them waiting up to 24 hours to see the change. A low TTL helps updates happen faster and keeps everything running smoothly.

Multiple CNAMEs

You can use multiple CNAME records to configure multiple custom domains for a site, but you must supply your own SSL Certificate in order to use your site with multiple domains.

While this approach requires manual configuration, it's helpful if you're supporting multiple brands with one site, handling legacy integrations that rely on an old custom domain, or to minimize downtime when switching between two custom domains.

When more than one CNAME record exists for a site, only one address is the primary custom domain address, and that address will be used on any links produced by the site, such as for Share Links or Inboxes, or for links in emails generated by Files.com.

Using CNAMEs That Aren't Registered in Files.com Is Not Recommended

Some customers have discovered that it is possible to configure a CNAME record from a domain they control to their .files.com subdomain without configuring it in Files.com as a custom domain. We strongly recommend against this practice because this will not result in a valid SSL certificate for the custom domain, and it will not provision any dedicated IP addresses.

Some customers do this for domains that will be accessed only through SFTP because SFTP doesn't use SSL certificates at all. This method of pointing a domain is unsupported.

Using DNS A Records Instead of CNAME (also called flattened CNAME)

Use of manually configured A records is not a good idea, and not supported. However, some DNS providers, such as Cloudflare, automatically "flatten" CNAMEs defined on the root of a domain to return A records rather than a hostname when the CNAME is resolved.

The DNS provider internally performs the additional queries needed to determine the actual IP and returns the result, just as if the CNAME was an A record. Flattening a CNAME can be helpful for modern web development, allowing you to use the root of your domain as the address for a service.

You can use a flattened CNAME for your site's custom domain. The DNS record must be configured to refresh rapidly (ideally every 60 seconds).

For a provider like Cloudflare, who also offers a proxying service in addition to DNS, be sure to disable proxying for your flattened CNAME records. Files.com does not support being wholly behind CloudFlare on your main site subdomain (though we do support this for public web hosting shares.

CAA Records

One additional pitfall with A Records and CNAME flattening is that they make CAA records a potential issue as well. If you use a CNAME, none of this section applies, because the CNAME automatically makes CAA records always work correctly.

A CAA Record is a security feature of the DNS system that allows domain name owners to restrict which issuers are allowed to issue SSL Certificates for a given domain.

If you are not using a valid CNAME record, and your Custom Domain has a CAA record set in your DNS, you might need to either update your CAA record to allow our Certificate Authority to issue certificates or provide your own certificate.

We issue certificates through a popular Certificate Authority called Let's Encrypt.

If you have a CAA DNS record for your custom domain, need to create another CAA record with the value letsencrypt.org, so we can issue the certificate.

If you need any help with this process, just let us know the service you're using to manage your DNS records, and we are happy to assist.