Dynamic DNS Domains

Available on: Free Plus Pro Elite

1. What This Feature Does

Dynamic DNS (DDNS) domains map a hostname to an IP address that can be updated automatically when the IP changes. You create a subdomain under a CertaDNS public zone (e.g., myserver.certadns.com) or under your own imported zone. When your public IP changes, you update the DNS record through the dashboard, the desktop client, or any DDNS-compatible router or script. The DNS record then resolves to your new IP.

Each domain stores a single A (IPv4) or AAAA (IPv6) record. The system tracks creation metadata (IP, country, timestamp) and every subsequent update in an audit log.

2. When You Should Use It

You have a home server, NAS, camera, or other device behind a dynamic IP and need a stable hostname pointing to it.
You run a game server or development environment on a residential connection where the ISP assigns IPs dynamically.
You want to access a remote network via VPN or SSH using a hostname instead of tracking a changing IP manually.
You want a router or client to automatically push IP updates without manual intervention.

3. When You Should Not Use It

Static hosting: If your server has a fixed IP that does not change, use the DNS Record Management feature on an imported zone instead. DDNS domains on public zones only support A and AAAA records.
MX, CNAME, TXT, or NS records: DDNS domains are limited to A and AAAA record types. For other record types, import your own zone and use the DNS Record Manager.
Web forwarding only: If you only need to redirect a hostname to a URL, see Web Forwarding.
Full zone management: If you need to manage an entire domain with multiple record types, use Managed DNS Zones.

4. Prerequisites

A registered CertaDNS account with a verified email address.
Free plan users: CAPTCHA completion is required on login.
To create domains under a custom zone: the zone must be imported and verified first (requires Plus or higher).
The IP address you want to assign must be a valid IPv4 address (for A records) or a valid IPv6 address (for AAAA records).

5. How It Works (Brief)

When you create a domain, CertaDNS writes an A or AAAA record to the authoritative DNS servers (PowerDNS). The record uses a TTL determined by your plan: 3600 seconds (60 minutes) on Free, or 60 seconds on paid plans. When you update the IP, the old record is replaced and the change propagates once the previous TTL expires at caching resolvers.

Subdomain names on CertaDNS public zones are validated against a blacklist of restricted names (e.g., admin, api, mail). This restriction does not apply to multi-level subdomains (e.g., my.admin.certadns.com) or to domains created under your own imported zones.

6. How to Use It

Creating a domain

Navigate to Dashboard > Domains.
Click Add Domain in the top right. (This button is disabled if you have reached your plan's domain limit.)
In the Add Domain modal:
- Enter a subdomain name (lowercase letters, numbers, and hyphens only).
- Select a zone from the dropdown. CertaDNS public zones and your imported zones are listed in separate groups.
- Select the record type: A (IPv4) or AAAA (IPv6). Default is A.
- Enter an IP address, or click Use Current to fill in your current public IP.
Click Add Domain.
The domain appears in the domain list with the IP you specified.

Updating a domain's IP

In the domain list, find the domain you want to update.
Click the edit icon (pencil) in the Actions column.
Enter the new IP address in the prompt.
Click OK. The IP updates immediately in the DNS.

You can also update domains via the API, desktop client, or router. See DDNS Update Protocols for details.

Deleting a domain

In the domain list, click the trash icon in the Actions column for the domain.
Confirm the deletion in the dialog.
The DNS record is removed from the authoritative servers. The domain is permanently deleted.

Bulk operations

Select domains using the checkboxes in the leftmost column. Use the header checkbox to select all visible domains.
The bulk actions bar appears at the top showing the count of selected domains.
Update All: Sets all selected domains to your current public IP. Only available if your current IP was detected.
Delete Selected: Deletes all selected domains after confirmation.
Clear Selection: Deselects all.

7. Inputs and Settings

Field	Description	Constraints
Subdomain	The hostname label placed before the zone. Displayed as a live preview (`subdomain.zone`).	Lowercase alphanumeric and hyphens. Each label max 63 characters. Total FQDN max 253 characters. Must start and end with a letter or number.
Zone	The parent domain. Choose from CertaDNS public zones or your imported zones.	Must be an active, available zone. Imported zones require verification.
Record Type	A (IPv4) or AAAA (IPv6).	Default: A. Cannot be changed after creation; delete and recreate to switch.
IP Address	The target IP for the DNS record.	Must be a valid IPv4 for A records or valid IPv6 for AAAA records. The "Use Current" button fills in your detected public IP.

TTL (Time to Live)

TTL is set automatically based on your plan and cannot be configured per-domain.

Plan	TTL
Free	3600 seconds (60 minutes)
Plus, Pro, Elite	60 seconds (1 minute)

8. Outputs and Results

Domain list columns

Column	Description
Domain	Full FQDN in monospace font. Wildcard domains show a purple "Wildcard" badge.
Zone	Parent zone name.
Status	Green "Active" or red "Inactive" badge.
Current IP	The A/AAAA record value in monospace, or "Not set" if no IP is assigned.
Monitoring	Green monitor icon if enabled, gray if disabled. Click to toggle.
Actions	Wildcard (sparkle icon, paid plans only), Update IP (pencil icon), Update Help (question mark icon), Delete (trash icon).

Filtering and sorting

Filter	Shows
All	All domains
CertaDNS	Domains on CertaDNS public zones only
UserZone	Domains on your imported zones (excludes wildcards)
Wildcard	Wildcard domains only
Monitored	Domains with monitoring enabled

Sort by: Name, IP, Type, or Status. Toggle ascending/descending with the sort order button.

Pagination options: 10, 25, 50, or 100 items per page. Changing filters resets to page 1.

API response

The domain list endpoint returns:

{
  "domains": [ ... ],
  "effective_plan": "plus",
  "max_domains": 50,
  "count": 12,
  "is_in_grace_period": false,
  "grace_period_ends": null
}

9. How to Interpret Results

Normal

Domain shows "Active" status and has an IP assigned. DNS lookups for the FQDN return the expected IP.
After updating, the new IP appears in the table immediately. External DNS resolvers may still return the old IP until the previous TTL expires.

Unexpected or worth investigating

"Not set" IP: The domain was created without an IP or the IP was never assigned. The DNS record exists but has no value. Update the IP to resolve this.
Domain is "Inactive": The domain record has been marked inactive. This typically occurs during account downgrades or administrative action.
IP does not match expected value: Verify the update was successful. Check if another client or router is also updating the same domain with a different IP.

Common interpretation mistakes

Expecting instant propagation: After an IP update, external resolvers will continue returning the old IP until the previous TTL expires. On the Free plan, this can be up to 60 minutes. On paid plans, up to 60 seconds.
Confusing FQDN with subdomain: The "Domain" column shows the full FQDN (e.g., myserver.certadns.com), not just the subdomain label.

10. Common Issues and Explanations

"Domain cap reached" error when adding a domain

You have reached the maximum number of domains for your plan. Delete unused domains or upgrade to a higher plan. Limits: Free=5, Plus=50, Pro=100, Elite=500.

"This subdomain is restricted" error

Certain subdomain names (e.g., admin, mail, www) are blocked on CertaDNS public zones. To use restricted names, import your own zone (requires Plus or higher) or use a multi-level subdomain (e.g., my.admin.certadns.com).

IP update succeeded in dashboard but DNS still returns old IP

Caching DNS resolvers retain the previous answer until the TTL expires. Wait for the TTL period (60 minutes on Free, 60 seconds on paid plans) before expecting the new IP to appear in all lookups. You can verify the authoritative answer directly by querying ns1.certadns.com or ns2.certadns.com.

"Invalid IP address" error on update

The IP must match the record type. A records require a valid IPv4 address (e.g., 192.168.1.1). AAAA records require a valid IPv6 address (e.g., 2001:db8::1). An IPv6 address submitted for an A record (or vice versa) is rejected.

Domain not found when updating via router or script

Verify the hostname parameter exactly matches the FQDN in your dashboard (e.g., myserver.certadns.com, not myserver). Check that authentication credentials (username/password or API key) are correct.

"Add Domain" button is disabled

You have reached your plan's domain limit. The button becomes active again when you delete a domain or upgrade your plan.

11. Limits and Constraints

Constraint	Free	Plus	Pro	Elite
Maximum domains	5	50	100	500
TTL	3600s	60s	60s	60s
Record types	A, AAAA	A, AAAA	A, AAAA	A, AAAA
API access for updates	No	Yes	Yes	Yes
Wildcard support	No	Yes	Yes	Yes
Custom zones	No	Yes	Yes	Yes

FQDN maximum length: 253 characters.
Each label (between dots) maximum length: 63 characters.
Subdomain names must be lowercase alphanumeric with hyphens. No underscores, spaces, or special characters.
On user-owned zones: 500 DNS records maximum per zone (this count includes DDNS domains and manually created DNS records combined).

12. Related Features

DDNS Update Protocols — Update domains via API, router, or desktop client instead of the dashboard.
Wildcard DNS — Create *.domain records that match any subdomain under a DDNS domain.
Managed DNS Zones (BYOD) — Import your own domain to use as a zone for DDNS records and other record types.
Web Forwarding — Redirect a DDNS domain to a URL instead of pointing it to an IP.
Uptime Monitoring — Monitor whether a DDNS domain's target is reachable.
DNS Analytics — View query volume and traffic patterns for your domains.

13. Updates and Behavior Changes

Subdomain limits on the Plus plan were increased from 25 to 50 subdomains.
Free plan CAPTCHA requirement was added to reduce automated abuse. Free users must complete a CAPTCHA on their initial login session.
Grace period support was added for canceled subscriptions. Users retain their paid plan features until the subscription end date.