Internet Assigned Numbers Authority

Concise Binary Object Representation (CBOR) Tags

Last Updated
Available Formats



Plain text

Registries included below


Carsten Bormann, Christian Amsüss
All registration requests must include the template from [RFC8949].
Available Formats

Range Registration Procedures
0-23 Standards Action
24-32767 Specification Required
32768-18446744073709551615 First Come First Served
Tag Data Item Semantics Reference Template
0 text string Standard date/time string; see Section 3.4.1 [RFC8949]
1 integer or float Epoch-based date/time; see Section 3.4.2 [RFC8949]
2 byte string Unsigned bignum; see Section 3.4.3 [RFC8949]
3 byte string Negative bignum; see Section 3.4.3 [RFC8949]
4 array Decimal fraction; see Section 3.4.4 [RFC8949]
5 array Bigfloat; see Section 3.4.4 [RFC8949]
6-15 Unassigned
16 COSE_Encrypt0 COSE Single Recipient Encrypted Data Object [RFC9052]
17 COSE_Mac0 COSE Mac w/o Recipients Object [RFC9052]
18 COSE_Sign1 COSE Single Signer Data Object [RFC9052]
19 COSE_Countersignature COSE standalone V2 countersignature [RFC9338]
20 Unassigned
21 (any) Expected conversion to base64url encoding; see Section [RFC8949]
22 (any) Expected conversion to base64 encoding; see Section [RFC8949]
23 (any) Expected conversion to base16 encoding; see Section [RFC8949]
24 byte string Encoded CBOR data item; see Section [RFC8949]
25 unsigned integer reference the nth previously seen string [][Marc_A._Lehmann]
26 array Serialised Perl object with classname and constructor arguments [][Marc_A._Lehmann]
27 array Serialised language-independent object with type name and constructor arguments [][Marc_A._Lehmann]
28 multiple mark value as (potentially) shared [][Marc_A._Lehmann]
29 unsigned integer reference nth marked value [][Marc_A._Lehmann]
30 array Rational number [][Peter_Occil]
31 Undefined (0xf7) Absent value in a CBOR Array [][Sami_Vaarala]
32 text string URI; see Section [RFC8949]
33 text string base64url; see Section [RFC8949]
34 text string base64; see Section [RFC8949]
35 UTF-8 string Regular expression; see Section [RFC7049]
36 text string MIME message; see Section [RFC8949]
37 byte string Binary UUID ([RFC9562, Section 4]) [][Lucas_Clemente]
38 array Language-tagged string [RFC9290, Appendix A]
39 multiple Identifier [][Lucas_Clemente]
40 array of two arrays [1] Multi-dimensional Array, row-major order [RFC8746]
41 array Homogeneous Array [RFC8746]
42 byte string IPLD content identifier [][Volker_Mische]
43 text string YANG bits datatype; see Section 6.7. [RFC9254]
44 text string YANG enumeration datatype; see Section 6.6. [RFC9254]
45 unsigned integer or text string YANG identityref datatype; see Section 6.10. [RFC9254]
46 unsigned integer or text string or array YANG instance-identifier datatype; see Section 6.13. [RFC9254]
47 unsigned integer YANG Schema Item iDentifier (sid); see Section 3.2. [RFC9254]
48 byte string IEEE MAC Address [RFC9542]
49-51 Unassigned
52 byte string or array IPv4, [prefixlen,IPv4], [IPv4,prefixpart] [RFC9164]
53 Unassigned
54 byte string or array IPv6, [prefixlen,IPv6], [IPv6,prefixpart] [RFC9164]
55-60 Unassigned
61 CBOR Web Token (CWT) CBOR Web Token (CWT) [RFC8392][Michael_B._Jones]
62 Unassigned
63 byte string Encoded CBOR Sequence [RFC8742] [draft-bormann-cbor-notable-tags-02, Section 2.1]
64 byte string uint8 Typed Array [RFC8746]
65 byte string uint16, big endian, Typed Array [RFC8746]
66 byte string uint32, big endian, Typed Array [RFC8746]
67 byte string uint64, big endian, Typed Array [RFC8746]
68 byte string uint8 Typed Array, clamped arithmetic [RFC8746]
69 byte string uint16, little endian, Typed Array [RFC8746]
70 byte string uint32, little endian, Typed Array [RFC8746]
71 byte string uint64, little endian, Typed Array [RFC8746]
72 byte string sint8 Typed Array [RFC8746]
73 byte string sint16, big endian, Typed Array [RFC8746]
74 byte string sint32, big endian, Typed Array [RFC8746]
75 byte string sint64, big endian, Typed Array [RFC8746]
76 byte string (reserved) [RFC8746]
77 byte string sint16, little endian, Typed Array [RFC8746]
78 byte string sint32, little endian, Typed Array [RFC8746]
79 byte string sint64, little endian, Typed Array [RFC8746]
80 byte string IEEE 754 binary16, big endian, Typed Array [RFC8746]
81 byte string IEEE 754 binary32, big endian, Typed Array [RFC8746]
82 byte string IEEE 754 binary64, big endian, Typed Array [RFC8746]
83 byte string IEEE 754 binary128, big endian, Typed Array [RFC8746]
84 byte string IEEE 754 binary16, little endian, Typed Array [RFC8746]
85 byte string IEEE 754 binary32, little endian, Typed Array [RFC8746]
86 byte string IEEE 754 binary64, little endian, Typed Array [RFC8746]
87 byte string IEEE 754 binary128, little endian, Typed Array [RFC8746]
88-95 Unassigned
96 COSE_Encrypt COSE Encrypted Data Object [RFC9052]
97 COSE_Mac COSE MACed Data Object [RFC9052]
98 COSE_Sign COSE Signed Data Object [RFC9052]
99 Unassigned
100 Unsigned or negative integer Number of days since the epoch date 1970-01-01 [RFC8943]
101 array [uint, any] alternatives as given by the uint + 128; see Section 9.1 [draft-bormann-cbor-notable-tags-07]
102 Unassigned
103 array Geographic Coordinates [][Danilo_Vidovic]
104 multiple Geographic Coordinate Reference System WKT or EPSG number [draft-clarke-cbor-crs]
105-109 Unassigned
110 byte string, array, or map relative object identifier (BER encoding); SDNV [RFC6256] sequence [RFC9090]
111 byte string, array, or map object identifier (BER encoding) [RFC9090]
112 byte string, array, or map object identifier (BER encoding), relative to [RFC9090]
113-119 Unassigned
120 multiple Internet of Things Data Point [][Danilo_Vidovic]
121-127 any alternatives 0..6, 1+1 encoding; see Section 9.1 [draft-bormann-cbor-notable-tags-07]
128-199 Unassigned
200 multiple Gordian Envelope [draft-mcnally-envelope-05]
201-255 Unassigned
256 multiple mark value as having string references [][Marc_A._Lehmann]
257 byte string Binary MIME message [][Peter_Occil]
258 array Mathematical finite set [][Alfredo_Di_Napoli]
259 map Map datatype with key-value operations (e.g. `.get()/.set()/.delete()`) [][Shane_Holloway]
260 byte string Network Address (IPv4 or IPv6 or MAC Address) (DEPRECATED in favor of 52 and 54 for IP addresses) [][Ravi_Raju][RFC9164]
261 map (IPAddress + Mask Length) Network Address Prefix (IPv4 or IPv6 Address + Mask Length) (DEPRECATED in favor of 52 and 54 for IP addresses) [][Ravi_Raju][RFC9164]
262 byte string Embedded JSON Object [][Ravi_Raju]
263 byte string Hexadecimal string [][Ravi_Raju]
264 array Decimal fraction with arbitrary exponent [][Peter_Occil]
265 array Bigfloat with arbitrary exponent [][Peter_Occil]
266 text string Internationalized resource identifier (IRI) [][Peter_Occil]
267 text string Internationalized resource identifier reference (IRI reference) [][Peter_Occil]
268 array Extended decimal fraction [][Peter_Occil]
269 array Extended bigfloat [][Peter_Occil]
270 array Extended rational number [][Peter_Occil]
271 DDoS Open Threat Signaling (DOTS) signal channel object DDoS Open Threat Signaling (DOTS) signal channel object, as defined in [RFC9132] [RFC9132]
272 byte string Non-UTF-8 CESU-8 string [][Sami_Vaarala]
273 byte string Non-UTF-8 WTF-8 string [][Sami_Vaarala]
274 byte string Non-UTF-8 MUTF-8 string [][Sami_Vaarala]
275 map (major type 5) Map contains only keys that are of type Text String (major type 3) [][Emile_Cormier]
276 byte string ERIS binary read capability []
277 byte string Universal Geographical Area Description (GAD) shape; see Section 5 [TS 23.032][Mathew_Meins]
278 byte string Universal Geographical Area Description (GAD) description of velocity; see Section 8 [TS 23.032][Mathew_Meins]
279-502 Unassigned
503-504 any Earmarked for CoRIM [draft-ietf-rats-corim]
505-508 Unassigned
509-549 any Earmarked for CoRIM [draft-ietf-rats-corim]
550-561 Unassigned
562-569 any Earmarked for CoRIM [draft-ietf-rats-corim]
570 map (spdm-toc-map, see CDDL) spdm-toc-map [TCG DICE Concise Evidence Binding for SPDM][TCG]
571 map (concise-evidence-map, see CDDL) concise-evidence-map [TCG DICE Concise Evidence Binding for SPDM][TCG]
572-599 any Earmarked for CoRIM [draft-ietf-rats-corim]
600-601 Unassigned
602 array Detached EAT Bundle [RFC-ietf-rats-eat-25, Section 5] [RFC-ietf-rats-eat-25]
603-1000 Unassigned
1001 map [RFC-ietf-cbor-time-tag-12] extended time [RFC-ietf-cbor-time-tag-12]
1002 map [RFC-ietf-cbor-time-tag-12] duration [RFC-ietf-cbor-time-tag-12]
1003 array [RFC-ietf-cbor-time-tag-12] period [RFC-ietf-cbor-time-tag-12]
1004 UTF-8 text string [RFC3339] full-date string [RFC8943]
1005-1009 Unassigned
1010 array: [id: text string, obj: any] Object type identifier [draft-rundgren-cotx-04]
1011-1039 Unassigned
1040 array of two arrays [1] Multi-dimensional Array, column-major order [RFC8746]
1041-1047 Unassigned
1048 byte string IEEE OUI/CID [RFC9542]
1049-1279 Unassigned
1280-1400 any alternatives 7..127, 1+2 encoding; see Section 9.1 [draft-bormann-cbor-notable-tags-07]
1401-18299 Unassigned
18300-18555 byte string Bare Hash value (COSE algorithm -256 to -1) [draft-bormann-cbor-notable-tags-09, Section 3.1.1]
18556 array [COSE algorithm identifier, Base Hash value] [draft-bormann-cbor-notable-tags-09, Section 3.1.1]
18557-18811 byte string Bare Hash value (COSE algorithm 1 to 255) [draft-bormann-cbor-notable-tags-09, Section 3.1.1]
18812-21064 Unassigned
21065 text string I-Regexp [draft-bormann-cbor-notable-tags-09, Section 2.1][draft-ietf-jsonpath-iregexp-08]
21066 Array[UTF8string, UTF8string?] ECMAScript RegExp [] [][Joe_Hildebrand]
21067-22097 Unassigned
22098 multiple hint that indicates an additional level of indirection [][Marc_A._Lehmann]
22099-25440 Unassigned
25441 Array containing at most one array followed by at most one map Capture [3] [][Geoffrey_Broadwell]
25442-32767 Unassigned
32768 unsigned integer Identifier for a FHIR constant [Stefan_Genchev] template/32768
32769 multiple External reference [][Christopher_Head]
32770-39999 Unassigned
40000 unsigned integer ur:known-value, Semantic signifier [][Wolf_McNally]
40001 byte string ur:digest, 32-byte SHA-256 digest [][Wolf_McNally]
40002 array ur:encrypted, IETF ChaCha20-Poly1305 ([RFC8439]) encrypted message [][Wolf_McNally]
40003 array ur:compressed, [RFC1951] DEFLATE-compressed message [][Wolf_McNally]
40004 multiple ur:request, Transaction Request identifier [][Wolf_McNally]
40005 multiple ur:response, Transaction response identifier [][Wolf_McNally]
40006 unsigned integer or text string ur:function, Envelope expression function identifier [][Wolf_McNally]
40007 unsigned integer or text string ur:parameter, Envelope expression parameter identifier [][Wolf_McNally]
40008 unsigned integer or text string ur:placeholder, Envelope expression placeholder identifier [][Wolf_McNally]
40009 unsigned integer or text string ur:replacement, Envelope expression replacement identifier [][Wolf_McNally]
40010 byte string ur:agreement-private-key, Curve25519 private key for X25519 key agreement [][Wolf_McNally]
40011 byte string ur:agreement-public-key, Curve25519 public key for X25519 key agreement [][Wolf_McNally]
40012 byte string ur:arid, Apparently Random Identifier [][Wolf_McNally]
40013 Unassigned
40014 byte string ur:nonce, Cryptographic nonce [][Wolf_McNally]
40015 array ur:password, Scrypt-hashed password [][Wolf_McNally]
40016 byte string ur:crypto-prvkeys, Private key base (key material) [][Wolf_McNally]
40017 array ur:crypto-pubkeys, Public key base (signing and agreement public key bundle) [][Wolf_McNally]
40018 byte string ur:salt, Random salt used for hash tree decorrelation [][Wolf_McNally]
40019 array ur:crypto-sealed, Encrypted message and ephemeral public key [][Wolf_McNally]
40020 multiple ur:signature, Cryptographic signature [][Wolf_McNally]
40021 byte string ur:signing-private-key, Cryptographic private key used for signing [][Wolf_McNally]
40022 multiple ur:signing-public-key, Cryptographic public key used for signing [][Wolf_McNally]
40023 byte string ur:crypto-key, Cryptographic key used for symmetric encryption [][Wolf_McNally]
40024-40299 Unassigned
40300 map ur:seed, Cryptographic seed [][Wolf_McNally]
40301-40302 Unassigned
40303 map ur:hdkey, Bitcoin BIP-32 HD key [][Wolf_McNally]
40304 map ur:keypath, Bitcoin BIP-32 key derivation path [][Wolf_McNally]
40305 map ur:coin-info, Cryptographic asset and network specifier [][Wolf_McNally]
40306 map ur:eckey, Bitcoin elliptic curve key (private or public) [][Wolf_McNally]
40307 map ur:address, Cryptocurrency address [][Wolf_McNally]
40308 map ur:output-descriptor, Bitcoin output descriptor [][Wolf_McNally]
40309 byte string ur:sskr, Sharded Secret Key Reconstruction (SSKR) shear [][Wolf_McNally]
40310 byte string ur:psbt, Partially Signed Bitcoin Transaction [][Wolf_McNally]
40311 map ur:account, Bitcoin output descriptor bundle [][Wolf_McNally]
40312-40799 Unassigned
40800 text string ur:ssh-private, Text format SSH private key [][Wolf_McNally]
40801 text string ur:ssh-public, Text format SSH public key [][Wolf_McNally]
40802 text string ur:ssh-signature, Text format SSH signature [][Wolf_McNally]
40803 text string ur:ssh-certificate, Text format SSH certificate [][Wolf_McNally]
40804-42599 Unassigned
42600 map A confidentiality clearance. The key value pairs of the map are defined in ADatP-4774.4 [Aidan_Murdock] template/42600
42601 array A metadata binding. The elements of the array are defined in AdatP-4778.5. The tag is also used as part of the magic number in on-disk detached and encapsulating bindings. [Aidan_Murdock] template/42601
42602 map A collection of NCMS metadata elements. The key value pairs of the map are defined in AdatP-5636.4 [Aidan_Murdock] template/42602
42603-42999 Unassigned
43000 array Single complex number: array elements are real (I) and imaginary (Q) components [Saajan_Chana] template/43000
43001 array Array of complex numbers in interleaved form: complex value k is stored with real (I) part at array index 2k and imaginary (Q) part at index (2k + 1) [Saajan_Chana] template/43001
43002-49999 Unassigned
50000 integer PlatformV_IS_ID [][Wang_Tongzhou]
50001 text string PlatformV_IS_NAME [][Wang_Tongzhou]
50002 any PlatformV_IS_VALUE [][Wang_Tongzhou]
50003 array PlatformV_HAS_COMPOSITE_VALUE [][Wang_Tongzhou]
50004 array PlatformV_HAS_MAPPED_VALUE [][Wang_Tongzhou]
50005 array PlatformV_HAS_OBJ_ID [][Wang_Tongzhou]
50006 array PlatformV_HAS_OBJ_TAG [][Wang_Tongzhou]
50007 array PlatformV_HAS_CHILD [][Wang_Tongzhou]
50008 array PlatformV_HAS_PROPERTY [][Wang_Tongzhou]
50009 array PlatformV_HAS_META [][Wang_Tongzhou]
50010 array PlatformV_HAS_EVENT [][Wang_Tongzhou]
50011 array PlatformV_HAS_ACTION [][Wang_Tongzhou]
50012 integer PlatformV_IS_TYPE [][Wang_Tongzhou]
50013-55798 Unassigned
55799 (any) Self-described CBOR; see Section 3.4.6 [RFC8949]
55800 tagged byte string indicates that the file contains CBOR Sequences [RFC9277]
55801 tagged byte string indicates that the file starts with a CBOR-Labeled Non-CBOR Data label. [RFC9277]
55802-56499 Unassigned
56500 array (major type 4) Compressed byte string [][Dirk_Boye]
56501-57341 Unassigned
57342 array Identify and define a set of record structures (each a sequence of property names) that can be referenced as tags in the included value (and the scope for the record tag definitions) [][Kris_Zyp]
57343 array Identify and define a record structure (a sequence of property names), and use that record structure definition to interpret the included values. [][Kris_Zyp]
57344-57599 array References a defined record structure, using that referenced record definition to interpret the included values. [][Kris_Zyp]
57600-59999 Unassigned
60000 array The tagged CBOR array contains attestation evidence data with an Intel TEE quote. [Shanwei_Cen] template/60000
60001 array The tagged CBOR array contains attestation evidence data with an Intel TEE report. [Shanwei_Cen] template/60001
60002 array The tagged CBOR array contains attestation evidence data with an Intel SGX report. [Shanwei_Cen] template/60002
60003-65534 Unassigned
65535 (none valid) always invalid; see Section 10.1 [draft-bormann-cbor-notable-tags-02]
65536-79999 Unassigned
80000-80099 byte string, array or map Private tags as suggested in []. [Tony_Putman] template/80000-80099
80100-15309735 Unassigned
15309736 map (major type 5) RAINS Message [][Brian_Trammell]
15309737-1330664269 Unassigned
1330664270 byte-string A CBOR encoded Openswan configuration file, as stored on disk for unit test cases. [Michael_Richardson][Samir_Hussain] template/1330664270
1330664271-1398229315 Unassigned
1398229316 map Concise Software Identifier (CoSWID) [RFC9393]
1398229317-1668546816 Unassigned
1668546817-1668612095 byte string or any CBOR data item (see Appendix B of [RFC9277]) the representation of content-format ct < 65025 is indicated by tag number TN(ct) = 0x63740101 + (ct / 255) * 256 + ct % 255 [RFC9277]
1668612096-1701996914 Unassigned
1701996915 array Array of content-addressed blocks and ERIS read capabilities [Endo_Renberg] template/1701996915
1701996916 array ERIS-FS image header [Endo_Renberg] template/1701996916
1701996917-4294967294 Unassigned
4294967295 (none valid) always invalid; see Section 10.1 [draft-bormann-cbor-notable-tags-02]
4294967296 map Intel FPGA SPDM Manifest [Andrew_Draper] template/4294967296
4294967297-18446744073709551614 Unassigned
18446744073709551615 (none valid) always invalid; Section 10.1 [draft-bormann-cbor-notable-tags-02]


Registration Procedure(s)
RFC and Expert Review Required
Available Formats

Timescale Value Semantics Reference
UTC 0 UTC with POSIX Epoch [RFC-ietf-cbor-time-tag-12]
TAI 1 TAI with PTP Epoch [RFC-ietf-cbor-time-tag-12]
Unassigned 2-18446744073709551615

Time Tag Map Keys

Registration Procedure(s)
Specification Required
Available Formats

Value Semantics Reference
-18446744073709551616..-19 Unassigned
-18 attoseconds [RFC-ietf-cbor-time-tag-12]
-15 femtoseconds [RFC-ietf-cbor-time-tag-12]
-12 picoseconds [RFC-ietf-cbor-time-tag-12]
-11 IXDTF Suffix Information (elective) [RFC-ietf-cbor-time-tag-12][draft-ietf-sedate-datetime-extended-11]
-10 IXDTF Time Zone Hint (elective) [RFC-ietf-cbor-time-tag-12][draft-ietf-sedate-datetime-extended-11]
-9 nanoseconds [RFC-ietf-cbor-time-tag-12]
-8 Guarantee [RFC-ietf-cbor-time-tag-12]
-7 Uncertainty [RFC-ietf-cbor-time-tag-12]
-6 microseconds [RFC-ietf-cbor-time-tag-12]
-5 Offset-Scaled Log Variance [RFC-ietf-cbor-time-tag-12]
-4 Clock Accuracy [RFC-ietf-cbor-time-tag-12]
-3 milliseconds [RFC-ietf-cbor-time-tag-12]
-2 Clock Class [RFC-ietf-cbor-time-tag-12]
1 base time value as in CBOR Tag 1 [RFC8949][RFC-ietf-cbor-time-tag-12]
4 base time value as in CBOR Tag 4 [RFC8949][RFC-ietf-cbor-time-tag-12]
5 base time value as in CBOR Tag 5 [RFC8949][RFC-ietf-cbor-time-tag-12]
10 IXDTF Time Zone Hint (critical) [RFC-ietf-cbor-time-tag-12][draft-ietf-sedate-datetime-extended-11]
11 IXDTF Suffix Information (critical) [RFC-ietf-cbor-time-tag-12][draft-ietf-sedate-datetime-extended-11]
12-18446744073709551615 Unassigned

Contact Information

ID Name Contact URI Last Updated
[Aidan_Murdock] Aidan Murdock mailto:aidan.murdock& 2022-05-24
[Alfredo_Di_Napoli] Alfredo Di Napoli mailto:alfredo.dinapoli& 2017-08-25
[Andrew_Draper] Andrew Draper mailto:andrew.draper& 2021-12-10
[Brian_Trammell] Brian Trammell mailto:ietf& 2016-08-17
[Christopher_Head] Christopher Head mailto:chead& 2022-12-28
[Danilo_Vidovic] Danilo Vidovic mailto:cbor& 2018-04-17
[Dirk_Boye] Dirk Boye mailto:dirk.boye& 2024-02-12
[Emile_Cormier] Emile Cormier mailto:emile.cormier.jr& 2020-03-30
[Endo_Renberg] Endo Renberg mailto:pukkamustard& 2023-07-31
[Geoffrey_Broadwell] Geoffrey Broadwell mailto:gjb& 2021-11-09
[Joe_Hildebrand] Joe Hildebrand mailto:joe-ietf& 2023-08-04
[Kris_Zyp] Kris Zyp mailto:kriszyp& 2022-05-23
[Lucas_Clemente] Lucas Clemente mailto:lucas& 2014-07-01
[Marc_A._Lehmann] Marc A. Lehmann mailto:cbor& 2013-11-26
[Mathew_Meins] Mathew Meins mailto:mm& 2021-02-01
[Michael_B._Jones] Michael B. Jones mailto:mbj& 2018-05-04
[Michael_Richardson] Michael Richardson mailto:mcr& 2021-01-25
[Peter_Occil] Peter Occil mailto:poccil14& 2018-11-09
[Ravi_Raju] Ravi Raju mailto:ravir& 2018-03-06
[Saajan_Chana] Saajan Chana mailto:saajan.chana& 2022-07-20
[Sami_Vaarala] Sami Vaarala mailto:sami.vaarala& 2020-03-18
[Samir_Hussain] Samir Hussain mailto:shussain& 2021-01-25
[Shane_Holloway] Shane Holloway mailto:shane.holloway& 2018-10-25
[Shanwei_Cen] Shanwei Cen mailto:shanwei.cen& 2023-01-12
[Stefan_Genchev] Stefan Genchev mailto:stefan.genchev& 2022-12-09
[TCG] Trusted Computing Group mailto:admin& 2024-03-20
[Tony_Putman] Tony Putman mailto:anthony.putman& 2023-04-26
[Volker_Mische] Volker Mische mailto:volker.mische& 2024-03-05
[Wang_Tongzhou] Wang Tongzhou 2022-10-20
[Wolf_McNally] Wolf McNally mailto:wolf& 2024-04-03


second element of outer array in data item is native CBOR array 
(major type 4) or Typed Array (one of Tag 64..87)