Dynu
- Free allowance
- 4 hostnames free (third-level names under Dynu domains, or your own domain), no expiry for an unused free account, REST API free for all users
- Verdict
- caveatusable, with a named limit or an unprobed read path
- Cost
- free tier
- Identity
- emailno card, no phone
- Binding limit
- per-object-cap4 hostnames and 4 subdomains free; the membership page's own figure is more than 3 third level domain names for members; up to 20 hostnames in one update request (numhost above 20)
- Evidence
- documented28 sources; a first-party page was read and the sentence quoted
- Freshness
- stale on 2026-12-04checked 2026-11-03 (live); stale on 2026-12-04
| Free tier | 4 hostnames free (third-level names under Dynu domains, or your own domain), no expiry for an unused free account, REST API free for all users unit objects; metered on object-count |
|---|---|
| Price | none stated |
| Limits |
|
| Binding | per-object-cap the hostname cap of 4 decides for a free account; the record-type gate matters only for CAA-class records |
| Identity | email the sign-up form asks for a first name, a last name, a username, a password and an e-mail address entered twice, or a sign-up with GitHub or Google; no phone or card field in the captured form text (https://www.dynu.com/en-US/ControlPanel/CreateAccount) |
| Egress | no DNS query cap published on the pages read |
| Per-object cap | 4 hostnames and up to 4 subdomains on the free plan per the FAQ; the membership page says members can have more than 3 third level domain names and 200 custom records, and no page read gives a free custom-record count (unverified) |
| Retention | Dynu accounts never expire; a free dynamic DNS service stays fully functional until the user deletes it |
| Interface | rest three update paths: a dyndns2-style HTTP update, GET https://api.dynu.com/nic/update?hostname=HOST&myip=IP&myipv6=IPV6&password=PASSWORD (the password may be sent as is or as an MD5 or SHA256 hash, and a separate IP update password can be set), up to 20 hostnames per request; HTTP and TCP GnuDIP at gnudip.dynu.com; and a REST API at https://api.dynu.com/v2/ with an API-Key header that manages hostnames and DNS records |
| Tooling | the free Dynu IP update clients for Windows, macOS and Linux, ddclient with protocol dyndns2, routers with a Dynu or Custom provider, GnuDIP clients, and curl against the REST API |
| Composes with | a free name that can also carry MX, TXT, SRV and CNAME records and a wildcard, on a Dynu domain or on a domain the user already owns that is served by Dynu name servers |
| Reliability | a failed update authentication returns HTTP 200 with the body badauth, so a status-only check reports success on a failed update; an unknown domain name can also return badauth |
| Notes | Confirmation interval: none; the dynamic DNS page states that accounts never expire. The free hostname count is 4 in the FAQ and the membership page implies 3, so the figure needs a re-read. |
| Evidence note | documented the dynamic DNS page, the FAQ, the membership page, the REST API page and the IP update protocol page were read and quoted; the update endpoint was probed once with a wrong password and answered 200 badauth. The free hostname count is 4 in the FAQ and implied as 3 by the membership page, so the figure is unreconciled |
| Parsed numbers |
|
Evidence 28
| date | source | what it proved |
|---|---|---|
| 2026-11-03 | www.dynu.com/FAQ/Dynamic-DNS-Service | the free plan allows 4 hostnames |
| 2026-11-03 | www.dynu.com/FAQ/Dynamic-DNS-Service | the free plan allows up to 4 subdomains |
| 2026-11-03 | www.dynu.com/en-US/Membership | the membership page gives its own figures for members: more than 3 third level domain names and 200 custom records |
| 2026-11-03 | www.dynu.com/FAQ/Dynamic-DNS-Service | A records are free on both a Dynu third-level name and an own domain |
| 2026-11-03 | www.dynu.com/FAQ/Dynamic-DNS-Service | TXT records are free on both a Dynu third-level name and an own domain |
| 2026-11-03 | www.dynu.com/FAQ/Dynamic-DNS-Service | CAA is a member-only record type |
| 2026-11-03 | www.dynu.com/en-US/DynamicDNS | accounts never expire, free users included, and the service works until deleted |
| 2026-11-03 | www.dynu.com/en-US/DynamicDNS | the service works with a top level domain name the user already owns |
| 2026-11-03 | www.dynu.com/en-US/Resources/API | the advanced REST API is free for all users |
| 2026-11-03 | www.dynu.com/en-US/Resources/API | the REST API manages hostnames and DNS records |
| 2026-11-03 | www.dynu.com/en-US/DynamicDNS/IP-Update-Protocol | the HTTPS update URL on api.dynu.com with hostname, myip, myipv6 and password |
| 2026-11-03 | www.dynu.com/en-US/DynamicDNS/IP-Update-Protocol | an update with more than 20 hostnames returns numhost |
| 2026-11-03 | www.dynu.com/en-US/DynamicDNS/IP-Update-Protocol | badauth is the response code for a failed authentication of the request |
| 2026-11-03 | www.dynu.com/en-US/DynamicDNS/IP-Update-Protocol | an unknown domain name sent as a parameter can also return badauth |
| 2026-11-03 | www.dynu.com/FAQ/Dynamic-DNS-Service | MX records are free on both a Dynu third-level name and an own domain |
| 2026-11-03 | www.dynu.com/FAQ/Dynamic-DNS-Service | wildcard DNS records are supported on Dynu third-level names and customer-owned domains |
| 2026-11-03 | www.dynu.com/en-US/DynamicDNS/IP-Update-Protocol | GnuDIP over TCP and HTTP is supported |
| 2026-11-03 | www.dynu.com/en-US/ControlPanel/CreateAccount | the sign-up form asks for the e-mail address twice |
| 2026-11-03 | www.dynu.com/en-US/ControlPanel/CreateAccount | the sign-up form offers a sign-up through Google |
| 2026-11-03 | probe: https://api.dynu.com/nic/update | the update endpoint is live and answers HTTP 200 to a request with a wrong password |
| 2026-11-03 | probe: body-dynu | the body of that failed update is the text code badauth, under HTTP 200 |
| 2026-11-03 | www.dynu.com/FAQ/Dynamic-DNS-Service | 4 hostnames free, up to 500 for a member |
| 2026-11-03 | www.dynu.com/FAQ/Dynamic-DNS-Service | up to 4 subdomains are free |
| 2026-11-03 | www.dynu.com/Membership | the membership page counts a different number of third level domain names for members |
| 2026-11-03 | www.dynu.com/ | the dynamic DNS service is free |
| 2026-11-03 | www.dynu.com/ | a free account comes with a free third level domain name or the user's own domain |
| 2026-11-03 | publicsuffix.org/list/public_suffix_list.dat | Dynu's suffixes (dynu.net, dynuddns.net) are entries of the private section of the Public Suffix List |
| 2026-11-03 | letsencrypt.org/docs/rate-limits/ | Let's Encrypt finds the registered domain with the Public Suffix List |