UCC/EAN-128 was developed to provide a worldwide standard for exchanging data between different companies. UCC/EAN-128 not only encodes the data, but provides a method of defining the meaning of the data by defining a list of "Application Identifiers" (A.I.).

UCC/EAN-128 is by itself not a symbology.

It is a standard that defines what kind of data is, how data is formatted. UCC/EAN-128 encodes data using Code128 symbology so the printing requirement of Code128 symbology still applies to UCC/EAN-128.

A typical UCC/EAN-128 barcode has the following structure:
1. A code128 start character(START-A, START-B or START-C)
2. A code128 FNC1 character
3. Application Identifier (AI)
4. Message encoded
5. Check character
6. Stop Character
7. Termination bar

Every UCC/EAN-128 symbol encodes an AI to indicate that what type of data is encoded. In most of cases, AI also decides the length of the data and the format of the data. All dates are represented in the format YYMMDD. YY values between 51-99 indicates the years between 1951 and 1999. YY values between 00-50 indicates the years between 2000 and 2050.

If the AI numbers contain an 'x' or 'y', that means a single digit needs to be appended to the AI. x digit indicates the length of the following data field; y digit indicates the ordinal of the decimal point in the data field.

AI	AI Description	Data Structure After AI Code
00	Serial Shipping Container Code (SSCC-18)	18 digits
01	Shipping Contained Code (SSCC-14)	14 Digits
02	Number of containers contained in another unit (used with AI 37)	14 Digits
10	Batch Numbers	1-20 Alphanumeric
11	Production Date	6 Digits: YYMMDD
13	Packaging Date	6 Digits: YYMMDD
15	Sell By Date (Quality Control)	6 Digits: YYMMDD
17	Expiration Date (Safety Control)	6 Digits: YYMMDD
20	Product Variant	2 Digits
21	Serial Number	1-20 Alphanumeric
22	HIBCC Quantity, Date, Batch and Link	1-29 Alphanumeric
23x	Lot Number	1-19 Alphanumeric
240	Additional Product Identification	1-30 Alphanumeric
250	Second Serial Number	1-30 Alphanumeric
30	Quantity Each	-
310y	Product Net Weight in Kg	6 Digits
311y	Product Length/1st Dimension (Meters)	6 Digits
312y	Product Width/Diameter/2nd Dimension (Meters)	6 Digits
313y	Product Depth/Thickness/3rd Dimension (Meters)	6 Digits
314y	Product Area (Square Meters)	6 Digits
315y	Product Volume (Liters)	6 Digits
316y	Product Volume (Cubic Meters)	6 Digits
320y	Product Net Weight (Pounds)	6 Digits
321y	Product Length/1st Dimension (Inches)	6 Digits
322y	Product Length/1st Dimension (Feet)	6 Digits
323y	Product Length/1st Dimension in (Yards)	6 Digits
324y	Product Width/Diamater/2nd Dimension (Inches)	6 Digits
325y	Product Width/Diameter/2nd Dimension (Feet)	6 Digits
326y	Product Width/Diameter/2nd Dimension (Yards)	6 Digits
327y	Product Depth/Thickness/Height/3rd Dimension (Inches)	6 Digits
328y	Product Depth/Thickness/Height/3rd Dimension (Feet)	6 Digits
329y	Product Depth/Thickness/Height/3rd Dimension (Yards)	6 Digits
330y	Container Gross Weight (Kg)	6 Digits
331y	Container Length/1st Dimension (Meters)	6 Digits
332y	Container Width/Diameter/2nd Dimension (Meters)	6 Digits
333y	Container Depth/Thickness/3rd Dimension (Meters)	6 Digits
334y	Container Area (Square Meters)	6 Digits
335y	Container Gross Volume (Liters)	6 Digits
336y	Container Gross Volume (Cubic Meters)	6 Digits
340y	Container Gross Weight (Pounds)	6 Digits
341y	Container Length/1st Dimension (Inches)	6 Digits
342y	Container Length/1st Dimension (Feet)	6 Digits
343y	Container Length/1st Dimension in (Yards) 6 Digits
344y	Container Width/Diamater/2nd Dimension (Inches)	6 Digits
345y	Container Width/Diameter/2nd Dimension (Feet)	6 Digits
346y	Container Width/Diameter/2nd Dimension (Yards)	6 Digits
347y	Container Depth/Thickness/Height/3rd Dimension (Inches)	6 Digits
348y	Container Depth/Thickness/Height/3rd Dimension (Feet)	6 Digits
349y	Container Depth/Thickness/Height/3rd Dimension (Yards)	6 Digits
350y	Product Area (Square Inches)	6 Digits
351y	Product Area (Square Feet)	6 Digits
352y	Product Area (Square Yards)	6 Digits
353y	Container Area (Square Inches)	6 Digits
354y	Container Area (Square Feet)	6 Digits
355y	Container Area (Suqare Yards)	6 Digits
356y	Net Weight (Troy Ounces)	6 Digits
360y	Product Volume (Quarts)	6 Digits
361y	Product Volume (Gallons)	6 Digits
362y	Container Gross Volume (Quarts)	6 Digits
363y	Container Gross Volume (Gallons)	6 Digits
364y	Product Volume (Cubic Inches)	6 Digits
365y	Product Volume (Cubic Feet)	6 Digits
366y	Product Volume (Cubic Yards)	6 Digits
367y	Container Gross Volume (Cubic Inches)	6 Digits
368y	Container Gross Volume (Cubic Feet)	6 Digits
369y	Container Gross Volume (Cubic Yards)	6 Digits
37	Number of Units Contained (Used with AI 02)	1-8 Digits
400	Customer Purchase Order Number	1-29 Alphanumeric
410	Ship To/Deliver To Location Code (EAN13 or DUNS code)	13 Digits
411	Bill To/Invoice Location Code (EAN13 or DUNS code)	13 Digits
412	Purchase From Location Code (EAN13 or DUNS code)	13 Digits
420	Ship To/Deliver To Postal Code (Single Postal Authority)	1-9 Alphanumeric
421	Ship To/Deliver To Postal Code (Multiple Postal Authority)	4-12 Alphanumeric
8001	Roll Products - Width/Length/Core Diameter	14 Digits
8002	Electronic Serial Number (ESN) for Cellular Phone	1-20 Alphanumeric
8003	UPC/EAN Number and Serial Number of Returnable Asset	14 Digit UPC +1-16 Alphanumeric Serial Number
8004	UPC/EAN Serial Identification	1-30 Alphanumeric
8005	Price per Unit of Measure	6 Digits
8100	Coupon Extended Code: Number System and Offer	6 Digits
8101	Coupon Extended Code: Number System, Offer, End of Offer	10 Digits
8102	Coupon Extended Code: Number System preceeded by 0	2 Digits
90	Mutually Agreed Between Trading Partners	1-30 Alphanumeric
91	Internal Company Codes	1-30 Alphanumeric
92	Internal Company Codes	1-30 Alphanumeric
93	Internal Company Codes	1-30 Alphanumeric
94	Internal Company Codes	1-30 Alphanumeric
95	Internal Company Carrieres	1-30 Alphanumeric
96	Internal Company Carrieres	1-30 Alphanumeric
97	Internal Company Codes	1-30 Alphanumeric
98	Internal Company Codes	1-30 Alphanumeric
99	Internal Company Codes	1-30 Alphanumeric