RFC 10023 Specification
Technical analysis and reference guide for the IETF Informational specification "The '_for-sale' Underscored and Globally Scoped DNS Node Name" (July 2026).
1. Motivation & Discovery Architecture
In the secondary domain market, discovering domains available for acquisition has historically been fragmented. Buyers must navigate browser popups, parked ad pages, heavily redacted Whois directories, or isolated marketplace silos.
RFC 10023 introduces a decentralized, protocol-native discovery layer within the Domain Name System. Domain owners need not alter nameservers or pay parking fees: a simple DNS TXT record announces sale availability across the global internet infrastructure.
2. The Reserved DNS Node (_for-sale)
Following RFC 8552 (Scoped, Underscored DNS Node Names), the specification adopts the _for-sale prefix. The underscore eliminates collisions with conventional hostnames (such as mail.example.com or www.example.com), which under RFC 1035 cannot contain underscores.
; Syntax per RFC 10023 Section 2.1 (Multi-Record RRset):
_for-sale.<domain-name>. 3600 IN TXT "v=FORSALE1;fval=EUR2500"
_for-sale.<domain-name>. 3600 IN TXT "v=FORSALE1;furi=https://<domain-name>/kontakt"
3. Tag-Value Specification (Section 2.1 & 2.2)
Under RFC 10023 Section 2.1, each TXT record must contain exactly one tag-value pair and begin with v=FORSALE1;. Multiple parameters are represented across separate records within the same Resource Record Set (RRset).
| Tag | Required | Meaning | Example Value |
|---|---|---|---|
| v | Yes | Version indicator. Must be exactly FORSALE1. | v=FORSALE1; |
| fval | Not validated (AD=0) | Fixed asking price per ISO 4217 currency code immediately preceding amount. Omitted for negotiable (OBO). | fval=EUR2500 |
| furi | Not validated (AD=0) | Contact URI (HTTP, HTTPS, mailto or tel conforming to RFC 3986). | furi=https://sedo.com/... |
| ftxt | Not validated (AD=0) | Human-readable description (e.g. negotiation terms, conditions). | ftxt=Inkl. Treuhand |
| fcod | Not validated (AD=0) | Machine transaction or verification tracking code. | fcod=AUTH-84920 |
4. Production Deployment: The SIDN Case Study (.nl)
The Dutch ccTLD registry SIDN (.nl) became the world’s first top-level registry to integrate RFC 10023 into its authoritative infrastructure. When a user queries domain availability on SIDN’s portal or Whois lookup, SIDN automatically checks for the _for-sale record. If present, the registrar immediately displays sale availability, price, and seller contact information.
Security Considerations (Section 4)
RFC 10023 does not define a native cryptographic settlement layer. Buyers should verify that the domain is signed with DNSSEC to prevent cache poisoning attacks, and are strongly encouraged to conclude transactions via licensed escrow services.