ISO record
IANA-assigned DNS record type for data coded according to an International Organization for Standardization specification.
Written and maintained by Ben Ennis
Last reviewed July 27, 2026 · How we verify this
Zone-file example
example.com. 3600 IN TYPE70 <standard-coded-value>Typical uses
- Publishing a value whose syntax is defined by an ISO specification and its consuming application
- Giving an external standards registry a DNS-native type assignment rather than overloading TXT
- Testing DNS software that implements the IANA external-registry type assignments
- Keeping a standards-defined value in a domain-controlled namespace for an interoperable client
When it breaks, check
- The IANA assignment does not define the ISO payload grammar or make a generic resolver understand it
- Do not publish an arbitrary string; follow the ISO specification and application profile exactly
- A successful response proves publication, not that a client accepts or validates the value
- Check authoritative, recursive, and client support independently when deploying the type
What the ISO record does
ISO belongs to the external-registry record-type assignments. A zone can publish data under the type when a consuming protocol has identified the ISO specification that defines the value. DNS transports the typed RDATA, while the application validates its structure, version, and meaning.
This is not a generic alternative to TXT. A browser will not use an ISO record to find a web server, and many DNS libraries will display it as an unknown type unless they know the assignment. Before publishing one, document the profile, owner name, expected encoding, and the software responsible for consuming it.
Zone-file and wire format
The wire type is ISO, with IANA value 70. The RDATA syntax is defined by the ISO specification selected by the application, not by the short IANA registry label alone. Use the profile’s exact field, length, character, and escaping rules in a zone file. A placeholder such as TYPE70 is useful for diagnostics, but is not a substitute for the profile-defined presentation format.
; illustrative placeholder only — use the profile-defined payload
example.com. 3600 IN TYPE70 <standard-coded-value>Common uses
Use ISO only when an application profile explicitly requires this IANA type. It can fit standards-driven data exchange where DNS is already the discovery namespace and the client knows how to validate the ISO-coded value. For ordinary text metadata, use TXT; for a service endpoint, compare SRV or HTTPS instead.
Troubleshooting
Begin with the application profile and verify the exact owner name, class, type value, and RDATA encoding. Query an authoritative server with a tool that can display unknown types, then compare recursive answers and TTLs. If the payload can be large, test TCP fallback and inspect truncation. Validate DNSSEC independently when the profile needs authenticated publication.
A client ignoring the record may simply lack support; the IANA assignment is not a mandate for every resolver or application to implement the ISO payload. Check the software and profile version before altering the zone.
dig example.com TYPE70 +noall +answer
# Query an authoritative server when diagnosing propagation.
dig @ns1.example.net example.com TYPE70 +norecurse +noall +answerThe defining RFC
ISO is DNS type 70 in the IANA DNS Parameters registry. The registry associates the type with an ISO-coded value and an external-registry template; the consuming ISO specification remains authoritative for the payload. Verify that profile before treating a published record as interoperable.
Reference and tooling
Every record type and its assigned numeric value is listed in theIANA DNS Parameters registry. To query a live zone from the browser, use theDNS lookup tool. If the record you are chasing is TLS-related, the TLS inspector andCertificate Transparency lookup are usually the next two stops.