Skip to main content
protocols.pageprotocols.page

CBOR Major Types

Every CBOR data item starts with a single byte. The upper 3 bits identify the major type (0-7). The lower 5 bits carry the argument or additional info. RFC 8949 §3.

0

Unsigned Integer

0x00

CBOR major type 0 encodes unsigned integers.

1

Negative Integer

0x20

CBOR major type 1 encodes negative integers.

2

Byte String

0x40

CBOR major type 2 encodes byte strings (raw binary data).

3

Text String

0x60

CBOR major type 3 encodes UTF-8 text strings.

4

Array

0x80

CBOR major type 4 encodes arrays (ordered sequences of data items).

5

Map

0xa0

CBOR major type 5 encodes maps (key-value pairs).

6

Tag

0xc0

CBOR major type 6 wraps a single data item with a semantic tag number.

7

Floating-Point and Simple Values

0xe0

CBOR major type 7 encodes simple values (false=0xf4, true=0xf5, null=0xf6, undefined=0xf7) and IEEE 754 floating-point numbers (half=0xf9, single=0xfa, double=0xfb).