CPI-var
Component/Part Identifier (variable length)
urn:epc:id:cpiWhat is CPI-var?
Variable-length CPI encoding with a 6-bit encoded alphanumeric component part reference (null-terminated) followed by a numeric serial.
Used for: Components requiring alphanumeric part references.
Field layout
The first 8 bits are always the header (0x3D = 61 decimal), which identifies this as CPI-var. The partition field determines how bits are divided between the company prefix and the following reference field - see the partition table below.
Defined in GS1 EPC Tag Data Standard v2.3, Section 7.11 (Component and Part Identifier), encoding procedure in Section 14.6.9.2.
| Bits | Field | Description |
|---|---|---|
0–7 | Header | 0x3D (61) - identifies this encoding as CPI-var |
8–10 | Filter | Same as CPI-96. |
11–13 | Partition | Same partition table as CPI-96. |
14–53 | Company Prefix | GS1 Company Prefix of the part manufacturer. |
54–59 | Component Part Reference | 6-bit encoded, null-terminated. Supports alphanumeric part numbers. |
60–95 | Serial | 36-bit numeric serial. |
Filter values
The 3-bit filter field does not affect identity - it tells readers what packaging level or category the tag is applied to. The same item with different filter values has the same Pure Identity URI.
Source: GS1 EPC TDS v2.3, Table 10-8.
| Value | Name | Description |
|---|---|---|
0 | All others | Unspecified component or part |
1 | Reserved | Not yet assigned |
2 | Reserved | Not yet assigned |
3 | Reserved | Not yet assigned |
4 | Reserved | Not yet assigned |
5 | Reserved | Not yet assigned |
6 | Reserved | Not yet assigned |
7 | Reserved | Not yet assigned |
Partition table
The 3-bit partition value determines how the fixed bit space is divided between the company prefix and the following reference field. GS1 company prefixes vary in length (6–12 digits), so the partition tells the decoder where one field ends and the next begins.
Source: GS1 EPC TDS v2.3, Table 14-34.
| Partition | Prefix bits | Prefix digits | Ref bits | Ref digits |
|---|---|---|---|---|
0 | 40 | 12 | 11 | 3 |
1 | 37 | 11 | 14 | 4 |
2 | 34 | 10 | 17 | 5 |
3 | 30 | 9 | 21 | 6 |
4 | 27 | 8 | 24 | 7 |
5 | 24 | 7 | 27 | 8 |
6 | 20 | 6 | 31 | 9 |
Related schemes
Source
GS1 EPC Tag Data Standard, Release 2.3, Ratified October 2025 - see Section 7.11 (Component and Part Identifier) and Section 14.6.9.2 for the encoding procedure. Read the EPC encoding guide for a full worked example of decoding hex to URI.