The "_for-sale" Underscored and Globally Scoped DNS Node Name

Internet-Draft	_for-sale DNS	November 2025
Davids	Expires 28 May 2026	[Page]

Abstract

This document defines an operational convention that uses the reserved underscored DNS leaf node name "_for-sale" to indicate that the parent domain name is available for purchase. The convention can be deployed without disrupting existing operations, and it may be applied even when the domain name is still actively in use.¶

1. Introduction

Well-established services [RFC3912][RFC9083] exist to determine whether a DNS domain name is registered. However, the fact that a domain name exists does not necessarily mean it is unavailable; it may still be for sale.¶

Some registrars and other parties offer brokerage services between domain name holders and interested buyers. Such services are of limited value when the domain name is not available for purchase, but they may be beneficial for domain names that are explicitly marked as for sale.¶

This specification defines a simple method to ascertain whether a domain name, although registered, is available for purchase. It enables a domain name holder to add a reserved underscored leaf node name [RFC8552] in the zone, indicating that the domain name is for sale. The indicator can be turned on and off at will and, moreover, it is immediately deployable and does not require significant changes in existing services, allowing for a smooth introduction of the concept.¶

The TXT RR type [RFC1035] created for this purpose must follow the formal definition of Section 2. Its content may contain a pointer, such as a Uniform Resource Identifier (URI) [RFC3986], an Internationalized Resource Identifier (IRI) [RFC3987] or another string, allowing interested parties to obtain information or contact the domain name holder for further negotiations. Details about whether and how such negotiations occur are out of scope.¶

With due caution, such information can also be incorporated into automated availability services. When checking a domain name for availability, the service may indicate whether it is for sale and provide a pointer to the seller's information.¶

The operational convention described in this document does not require any protocol change.¶

Furthermore, Section 6 discusses some ethical considerations. In particular, the approach in this document aims to promote a more equitable domain aftermarket and to minimise the potential for unintended commercial entanglements by registries.¶

Examples are provided in Appendix A.¶

1.1. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶

Although the document defines an operational convention rather than a protocol extension, normative language is used to promote consistent and unambiguous behaviours among entities that adopt the convention.¶

The term "processor" refers to an entity (person, system, or service) that reads, interprets, and takes appropriate actions based on "_for-sale" DNS labels, whether manually or automatically.¶

The term "for sale" is used in a broad sense and may also refer to cases where the domain name is available for lease, or where the contractual right to use the domain name is offered to another party.¶

2. Conventions

2.1. General Record Format

Each "_for-sale" TXT record MUST begin with a version tag, optionally followed by a string containing content that follows a simple "tag=value" syntax.¶

The formal definition of the record format, using ABNF [RFC5234][RFC7405], is as follows:¶

forsale-record  = forsale-version [forsale-content]
                  ; referred to as 'content' or RDATA
                  ; in a single character-string

forsale-version = %s"v=FORSALE1;"
                  ; %x76.3D.46.4F.52.53.41.4C.45.31.3B
                  ; version tag, case-sensitive, no spaces

forsale-content = fcod-pair / ftxt-pair / furi-pair / fval-pair
                  ; referred to as 'tag-value pairs'
                  ; only one tag-value pair per record

fcod-pair       = fcod-tag fcod-value
ftxt-pair       = ftxt-tag ftxt-value
furi-pair       = furi-tag furi-value
fval-pair       = fval-tag fval-value
                  ; the tags are referred to as 'content tags'
                  ; the values are referred to as 'content values'

fcod-tag        = %s"fcod="
ftxt-tag        = %s"ftxt="
furi-tag        = %s"furi="
fval-tag        = %s"fval="
                  ; all content tags case-sensitive lowercase

fcod-value      = 1*239OCTET

ftxt-value      = 1*239OCTET

furi-value      = URI / IRI
                  ; http, https, mailto and tel URI schemes
                  ; exactly one URI or IRI

URI             = <as defined in RFC3986, Appendix A>
IRI             = <as defined in RFC3987, Section 2.2>

fval-value      = fval-currency fval-amount
                  ; total length: 2 to 239 characters
fval-currency   = 1*%x41-5A
                  ; one or more uppercase letters (A-Z)
                  ; indicating (crypto)currency
                  ; e.g., USD, EUR, BTC, ETH
                  ; standard three-letter fiat currencies recommended
fval-amount     = int-part [ %x2E frac-part ]
                  ; integer part with optional fractional part
                  ; e.g., 0.00010
int-part        = 1*DIGIT
frac-part       = 1*DIGIT

See Section 2.2 for more detailed format definitions per content tag type.¶

Each "_for-sale" TXT record MUST NOT contain more than one tag-value pair, but multiple TXT records MAY be present in a single RRset.¶

Every tag-value pair in the RRset MUST be unique, but multiple instances of the same content tag MAY occur within a single RRset (e.g., two "fcod=" content tags, each with a different content value).¶

See Section 2.4 for additional RRset limitations.¶

The OPTIONAL forsale-content provides information to interested parties as explained in Section 1.¶

If the forsale-content is absent or invalid, but a valid version tag is present, processors SHOULD assume that the domain is for sale unless a local policy indicates otherwise. For example:¶

_for-sale.example.com. IN TXT "v=FORSALE1;"
_for-sale.example.com. IN TXT "v=FORSALE1;fcod="
_for-sale.example.com. IN TXT "v=FORSALE1;foo=bar"

In such cases, processors determine how to proceed. An approach might be to signal that the domain is for sale and to rely on conventional mechanisms (e.g., WHOIS or Registration Data Access Protocol (RDAP)) to retrieve and present contact information.¶

TXT records in the same RRset, but without a version tag, MUST NOT be interpreted or processed as a valid "_for-sale" indicator. However, they may still offer some additional information for humans when considered alongside a valid record. For example:¶

_for-sale.example.com. IN TXT "I am for sale"
_for-sale.example.com. IN TXT "v=FORSALE1;fcod=XX-NGYyYjEyZWY"

If no TXT records at a leaf node contain a valid version tag, processors MUST consider the node name invalid and MUST discard it.¶

See Section 2.3 for additional content limitations.¶

2.2. Content Tag Type Definitions

The following content tags are defined as valid content tags.¶

Content tags are optional. Providing a minimum set to allow interested parties to engage is RECOMMENDED.¶

2.2.1. fcod

This content tag is intended to contain a code that is meaningful only to processors that understand its semantics. The content value MUST consist of at least one octet.¶

The manner in which the "fcod=" content tag is used is determined by agreement between cooperating parties.¶

For example, a domain name registry may allow registrars to enter a "for sale" URL into their system. From that URL, a unique code is generated. This code is inserted as the value of the "fcod=" content tag of the "_for-sale" TXT record of a domain name, as shown in the example below.¶

When a user checks the availability of the domain name using a registry-provided tool (e.g., a web interface), the domain name registry may use the code to redirect the user to the appropriate "for sale" URL, which may include a query component containing the domain name, for example:¶

https://forsale-url.example.com/acme?d=example.org

The rationale for this approach is that controlling parties retain authority over redirection URLs and any other information derived from the content tag, thereby preventing users from being sent to unintended or malicious destinations or from being presented with unintended content.¶

The following example shows a string encoded using Base64 [RFC4648] preceded by the prefix "ACME-" as the value of the content tag:¶

_for-sale IN TXT "v=FORSALE1;fcod=ACME-S2lscm95IHdhcyBoZXJl"

See the Additional Examples section for other possible uses of this content tag.¶

Note: As an implementation consideration, when multiple parties are involved in the domain sale process and use the same mechanism, it may be difficult to identify the relevant content in an RRset. Adding a recognizable prefix to the content (e.g., "ACME-") is one possible approach. However, this is left to the implementor, as it is not enforced in this document. In this case, ACME would recognise its content tag and interpret it as intended. This example uses Base64 encoding to avoid escaping and ensure printable characters, though this is OPTIONAL and not required.¶

2.2.2. ftxt

This content tag is intended to contain human-readable text that conveys additional information to interested parties. For example:¶

_for-sale IN TXT "v=FORSALE1;ftxt=Call for info."

While a single octet is the minimum, it is RECOMMENDED to provide more context.¶

While a URI in this field is not syntactically prohibited, its interpretation as a URI is not guaranteed. Use of URIs in this field SHOULD be avoided in favor of the "furi=" content tag.¶

See Section 2.2.4 for a way to explicitly indicate an asking price for easier machine parsing.¶

See Section 3.2 for considerations regarding the representation of non-ASCII data in the content value.¶

2.2.3. furi

This content tag is intended to contain a human-readable and machine-parsable URI that can be used by interested parties to retrieve further information.¶

While the syntax allows any URI scheme, only the following schemes are RECOMMENDED for use: http and https [RFC9110], mailto [RFC6068][RFC6530] (Section 11.1), and tel [RFC3966].¶

The content value MUST contain exactly one URI. For example:¶

_for-sale IN TXT "v=FORSALE1;furi=https://example.com/foo%20bar"

URIs MUST conform to the syntax and encoding requirements specified in Section 2.1 of [RFC3986], including the percent-encoding of characters not allowed unencoded (e.g., spaces must be encoded as %20 in a URI).¶

Section 3.2 provides additional guidelines on character encoding.¶

See the Security Considerations section for possible risks.¶

Note: References to a URI in this document also encompass IRIs [RFC3987].¶

2.2.4. fval

This content tag is intended to contain human-readable and machine-parsable text that explicitly indicates an asking price in a certain currency.¶

Price information is commonly published by domain sellers. The "fval=" content tag provides a structured format for this purpose, enabling reliable machine parsing and reducing ambiguity compared to embedding prices in free-form "ftxt=" content tags. For example:¶

_for-sale IN TXT "v=FORSALE1;fval=EUR999"

The information provided in "fval=" is not binding. For current and reliable information, interested parties SHOULD engage directly with the seller via "furi=" or conventional mechanisms.¶

See Section 3.3 for additional operational guidelines and the Security Considerations section for possible risks.¶

2.2.5. Future Tags

Future tags may be defined to accommodate operational needs. Future content tags MUST NOT alter the semantics of existing content tags.¶

A tag name length of 4 characters is RECOMMENDED for consistency with the initial tag set and to maintain compact record formats.¶

2.3. Content Limitations

The "_for-sale" TXT record [RFC8553] (Section 2.1) MUST contain content deemed valid under this specification.¶

Any text suggesting that a domain is not for sale is invalid content. If a domain name is not or no longer for sale, a "_for-sale" indicator SHOULD NOT exist. The presence of a valid "_for-sale" TXT record SHOULD therefore be regarded as an indication that the domain name is for sale.¶

The existence of a "_for-sale" leaf node does not obligate the holder to sell the domain name; it may have been published in error, or withdrawn later for other reasons.¶

This specification does not dictate the exact use of any content values in the "_for-sale" TXT record. Parties may use it in their tools, perhaps even by defining specific requirements that the content value must meet. Content values can also be represented in a human-readable format for individuals to interpret. See the Additional Examples section for clarification.¶

See Section 3 for additional guidelines.¶

2.4. RRset Limitations

This document does not impose a limit on the number of TXT records in the RRset of "_for-sale" TXT records.¶

When multiple "_for-sale" TXT records are present in an RRset, the processor MAY select one or more of them.¶

For example, a domain name registry might extract content from an RRset that includes a recognizable "fcod=" content tag and use it to direct visitors to a sales page as part of its services. An individual, on the other hand, might extract a phone number (if present) from a "furi=" tag in the same RRset and use it to contact a potential seller.¶

An example of such a combined record is provided in Appendix A.5.¶

The RDATA [RFC9499] of each "_for-sale" TXT record MUST consist of a single character-string [RFC1035] with a maximum length of 255 octets, to avoid the need to concatenate multiple character-strings during processing.¶

The following example illustrates an invalid "_for-sale" TXT record due to the presence of multiple character-strings:¶

_for-sale IN TXT "v=FORSALE1;" "ftxt=foo" "bar" "invalid"

2.5. Wildcard Limitation

Wildcards are only interpreted as leaf names, so "_for-sale.*.example." is not a valid wildcard [RFC4592] and is non-conformant. Hence, it is not possible to put all domains under a TLD for sale with just one "_for-sale" TXT record.¶

The example below, however, shows a common use case where a "_for-sale" leaf node exists alongside a wildcard:¶

*         IN A    198.51.100.80
          IN AAAA 2001:db8::80
_for-sale IN TXT  "v=FORSALE1;ftxt=Only $99 at ACME"

2.6. Placement of the Leaf Node Name

The "_for-sale" leaf node name can essentially be placed at any level of the DNS except in the in-addr.arpa. infrastructure TLD.¶

Table 1 illustrates this:¶

Table 1: Placements of TXT record
Name	Situation	Verdict
_for-sale.example.	root zone	For sale
_for-sale.aaa.example.	second level	For sale
_for-sale.acme.bbb.example.	third level with public registry	For sale
_for-sale.www.ccc.example.	third level without public registry	See note 1
_for-sale.51.198.in-addr.arpa.	infrastructure TLD	See note 2
xyz._for-sale.example.	Invalid placement, not a leaf	non-conformant

Note 1: When the "_for-sale" leaf node is applied to a label under a subdomain, there may not be a public domain name registry [RFC9499] capable of properly recording the rights associated with that label. Nevertheless, this does not constitute a violation of this document. One possible approach is for the involved parties to establish a mutual agreement to formalize these rights.¶

Note 2: If a "_for-sale" leaf node were to appear under the .arpa infrastructure top-level domain, it might be interpreted as an offer to sell IP address space. However, such use is explicitly out of scope for this document, and processors MUST ignore any such records.¶

3. Operational Considerations

3.1. DNS Wildcards

DNS wildcards interact poorly with underscored names [RFC8552] (Section 1.4), but they may still be encountered in practice, especially with operators who are not implementing this mechanism. This is why the version tag is a mandatory element: it allows processors to distinguish valid "_for-sale" records from unrelated TXT records.¶

Nonetheless, any assumptions about the content of "_for-sale" TXT records should be made with caution, particularly in edge cases where wildcard expansion - possibly combined with DNS aliases (e.g., CNAMEs) or redirections (e.g., DNAMEs [RFC6672]) - might result in misleading listings or unintended references to third-party domains.¶

3.2. Handling of RDATA

Since this method relies on DNS TXT records, standard content rules apply as defined in [RFC1035] (Section 5.1). This includes the possibility of representing non-ASCII data in the content value, by using escape sequences (e.g., \DDD or \X notation).¶

All text in content values exchanged between systems that are not part of a closed ecosystem SHALL be encoded in and interpreted as UTF-8 [RFC3629] and conform to the Network Unicode format [RFC5198]. The allowed subset of Unicode code points SHOULD conform to [RFC9839] (Section 4.3), with the exception of %x09, %x0A and %x0D which MUST NOT be used.¶

See Section 3.6 for additional guidelines and the Security Considerations section for possible risks.¶

Internationalized Domain Names (IDN) MAY be expressed as A-labels as well as U-labels [RFC5890], with U-labels encoded using escape sequences as described above.¶

Processors MUST be capable of handling such encodings to ensure that non-ASCII content values are correctly interpreted and represented.¶

Note: When non-ASCII data is used, the ABNF octet limit applies to the encoded byte sequence, not the number of visible characters. Multi-byte characters will reduce the available character count.¶

For example, this TXT record contains two Japanese Kanji characters encoded in UTF-8 using octal escapes, resulting in a content value of six octets.¶

_for-sale IN TXT "v=FORSALE1;ftxt=\229\163\178\229\135\186"

3.3. Currency

The ABNF in Section 2.1 allows currency codes consisting of one or more uppercase letters, providing flexibility to accommodate both standard fiat currencies and other widely recognized abbreviations, such as cryptocurrencies.¶

The use of standard fiat currencies is RECOMMENDED. When used, they MUST be represented by three-letter uppercase currency codes as specified in [ISO4217] (e.g., USD, EUR, GBP and JPY).¶

The amount component consists of an integer part, optionally followed by a fractional part separated by a decimal point (%x2E, ".").¶

3.4. TTLs

Long TTLs [RFC1035] (Section 3.2.1) increase the risk of outdated data misleading buyers into thinking the domain is still available or that advertised prices remain current.¶

A TTL of 3600 seconds (1 hour) or less is RECOMMENDED.¶

3.5. Ambiguous Constructs

Ambiguous constructs in content values SHOULD be avoided, as illustrated by the following example:¶

_for-sale IN TXT "v=FORSALE1;fcod=TRIP-confusing;ftxt=dont_do_this"

The above example is a valid "fcod=" content tag that includes the string ";ftxt=" in the content value, which may be confusing, as it does not actually represent an "ftxt=" content tag.¶

3.6. Robustness

Because the format of the content part is not strictly defined in this document, processors MAY apply the robustness principle of being liberal in what they accept. This also applies to space characters (%x20) immediately following the version tag.¶

Alternatively, parties may agree on a more strictly defined proprietary format for the content value to reduce ambiguity. However, it is out of scope to discuss which mechanisms are put in place for such agreements.¶

When encountering unexpected or prohibited control characters in "ftxt=" content (e.g., %x09, %x0A, %x0B, %x0D, see Section 3.2), processors MAY sanitize them (e.g., by converting to spaces (%x20) or removing them entirely) before display or processing to ensure correct representation.¶

3.7. Scope of Application

The "_for-sale" mechanism relies upon the domain name being resolvable in the DNS. This is not guaranteed, for example, during a redemption period, in pendingDelete status [STD69], or when the domain is DNSSEC-signed but fails validation (i.e., has a bogus state).¶

Table 2: Entry for the "Underscored and Globally Scoped DNS Node Names" registry
RR Type	_NODE NAME	Reference
TXT	_for-sale	<this memo>

9. References

9.1. Normative References

[ISO4217]: SIX Group, "ISO 4217 Currency Codes", <https://www.iso.org/iso-4217-currency-codes.html>.
[RFC1035]: Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC2119]: Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.
[RFC3629]: Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 2003, <https://www.rfc-editor.org/info/rfc3629>.
[RFC3986]: Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, <https://www.rfc-editor.org/info/rfc3986>.
[RFC3987]: Duerst, M. and M. Suignard, "Internationalized Resource Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987, January 2005, <https://www.rfc-editor.org/info/rfc3987>.
[RFC5234]: Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC5234, January 2008, <https://www.rfc-editor.org/info/rfc5234>.
[RFC5890]: Klensin, J., "Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework", RFC 5890, DOI 10.17487/RFC5890, August 2010, <https://www.rfc-editor.org/info/rfc5890>.
[RFC7405]: Kyzivat, P., "Case-Sensitive String Support in ABNF", RFC 7405, DOI 10.17487/RFC7405, December 2014, <https://www.rfc-editor.org/info/rfc7405>.
[RFC8174]: Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC9839]: Bray, T. and P. Hoffman, "Unicode Character Repertoire Subsets", RFC 9839, DOI 10.17487/RFC9839, August 2025, <https://www.rfc-editor.org/info/rfc9839>.

9.2. Informative References

[RFC3912]: Daigle, L., "WHOIS Protocol Specification", RFC 3912, DOI 10.17487/RFC3912, September 2004, <https://www.rfc-editor.org/info/rfc3912>.
[RFC3966]: Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966, DOI 10.17487/RFC3966, December 2004, <https://www.rfc-editor.org/info/rfc3966>.
[RFC4592]: Lewis, E., "The Role of Wildcards in the Domain Name System", RFC 4592, DOI 10.17487/RFC4592, July 2006, <https://www.rfc-editor.org/info/rfc4592>.
[RFC4648]: Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, <https://www.rfc-editor.org/info/rfc4648>.
[RFC5198]: Klensin, J. and M. Padlipsky, "Unicode Format for Network Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008, <https://www.rfc-editor.org/info/rfc5198>.
[RFC6068]: Duerst, M., Masinter, L., and J. Zawinski, "The 'mailto' URI Scheme", RFC 6068, DOI 10.17487/RFC6068, October 2010, <https://www.rfc-editor.org/info/rfc6068>.
[RFC6530]: Klensin, J. and Y. Ko, "Overview and Framework for Internationalized Email", RFC 6530, DOI 10.17487/RFC6530, February 2012, <https://www.rfc-editor.org/info/rfc6530>.
[RFC6672]: Rose, S. and W. Wijngaards, "DNAME Redirection in the DNS", RFC 6672, DOI 10.17487/RFC6672, June 2012, <https://www.rfc-editor.org/info/rfc6672>.
[RFC8552]: Crocker, D., "Scoped Interpretation of DNS Resource Records through "Underscored" Naming of Attribute Leaves", BCP 222, RFC 8552, DOI 10.17487/RFC8552, March 2019, <https://www.rfc-editor.org/info/rfc8552>.
[RFC8553]: Crocker, D., "DNS Attrleaf Changes: Fixing Specifications That Use Underscored Node Names", BCP 222, RFC 8553, DOI 10.17487/RFC8553, March 2019, <https://www.rfc-editor.org/info/rfc8553>.
[RFC9083]: Hollenbeck, S. and A. Newton, "JSON Responses for the Registration Data Access Protocol (RDAP)", STD 95, RFC 9083, DOI 10.17487/RFC9083, June 2021, <https://www.rfc-editor.org/info/rfc9083>.
[RFC9110]: Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, Ed., "HTTP Semantics", STD 97, RFC 9110, DOI 10.17487/RFC9110, June 2022, <https://www.rfc-editor.org/info/rfc9110>.
[RFC9499]: Hoffman, P. and K. Fujiwara, "DNS Terminology", BCP 219, RFC 9499, DOI 10.17487/RFC9499, March 2024, <https://www.rfc-editor.org/info/rfc9499>.
[STD69]: Internet Standard 69, <https://www.rfc-editor.org/info/std69>.
At the time of writing, this STD comprises the following:

Hollenbeck, S., "Extensible Provisioning Protocol (EPP)", STD 69, RFC 5730, DOI 10.17487/RFC5730, August 2009, <https://www.rfc-editor.org/info/rfc5730>.

Hollenbeck, S., "Extensible Provisioning Protocol (EPP) Domain Name Mapping", STD 69, RFC 5731, DOI 10.17487/RFC5731, August 2009, <https://www.rfc-editor.org/info/rfc5731>.

Hollenbeck, S., "Extensible Provisioning Protocol (EPP) Host Mapping", STD 69, RFC 5732, DOI 10.17487/RFC5732, August 2009, <https://www.rfc-editor.org/info/rfc5732>.

Hollenbeck, S., "Extensible Provisioning Protocol (EPP) Contact Mapping", STD 69, RFC 5733, DOI 10.17487/RFC5733, August 2009, <https://www.rfc-editor.org/info/rfc5733>.

Hollenbeck, S., "Extensible Provisioning Protocol (EPP) Transport over TCP", STD 69, RFC 5734, DOI 10.17487/RFC5734, August 2009, <https://www.rfc-editor.org/info/rfc5734>.

Appendix A. Additional Examples

A.1. Example 1: Code Format

A proprietary format, defined and used by agreement between parties - for example, a domain name registry and its registrars - without a clearly specified meaning for third parties. For example, it may be used to automatically redirect visitors to a web page, as described in Section 2.2.1:¶

_for-sale IN TXT "v=FORSALE1;fcod=XX-aHR0cHM...wbGUuY29t"

Note: the content value in the above example is truncated for readability.¶

The use of the "fcod=" content tag is, in principle, unrestricted, allowing implementers to define additional uses as needed. For example, it may convey arbitrary formatting or conditional display instructions, such as adding an extra banner (e.g., "eligibility criteria apply") or specifying a style, including color, font, emojis, or logos.¶

A.2. Example 2: Free Text Format

Free format text, with some additional unstructured information, aimed at being human-readable:¶

_for-sale IN TXT "v=FORSALE1;ftxt=Eligibility criteria apply."

The content in the following example could be malicious, but it is not in violation of this specification (see the Security Considerations):¶

_for-sale IN TXT "v=FORSALE1;ftxt=<script>...</script>"

A.3. Example 3: URI Format

The holder of "example.com" wishes to signal that the domain is for sale and adds this record to the "example.com" zone:¶

_for-sale IN TXT "v=FORSALE1;furi=https://example.com/fs?d=eHl6"

An interested party notices this signal and can visit the URI mentioned for further information. The TXT record may also be processed by automated tools, but see the Security Considerations section for possible risks.¶

As an alternative, a mailto: URI could also be used:¶

_for-sale IN TXT "v=FORSALE1;furi=mailto:hq@example.com?subject=foo"

Or a telephone URI:¶

_for-sale IN TXT "v=FORSALE1;furi=tel:+1-201-555-0123"

There can be a use case for these URIs, especially since WHOIS (or RDAP) often has privacy restrictions. But see the Privacy Considerations section for possible downsides.¶

A.4. Example 4: Asking Price Format

Consists of an uppercase currency code (e.g., USD, EUR), followed by a numeric amount. See Section 3.3 for additional guidelines.¶

In Bitcoins:¶

_for-sale IN TXT "v=FORSALE1;fval=BTC0.000010"

In US dollars:¶

_for-sale IN TXT "v=FORSALE1;fval=USD750"

A.5. Example 5: Combinations

An example of multiple valid TXT records from which a processor can choose:¶

_for-sale IN TXT "v=FORSALE1;furi=https://fs.example.com/"
          IN TXT "v=FORSALE1;ftxt=This domain name is for sale"
          IN TXT "v=FORSALE1;fval=EUR500"
          IN TXT "v=FORSALE1;fcod=ACME-ZGVhZGJlZWYx"
          IN TXT "v=FORSALE1;fcod=XYZ1-MTExLTIyMi0zMzMtNDQ0"