Serial number duplicate and range check
Paste serial numbers or a CSV column. The tool reports duplicates, consecutive ranges and the gaps between them, length and character inconsistencies, and values damaged by spreadsheet software; you can copy the summary.
One number per line, or a delimited table (; , tab). If there are several columns choose the column to check below. At most 200,000 rows. The check only compares the list you paste; a serial number must be unique per GTIN, so paste the list of a single product (GTIN).
Input options
The check runs in your browser; the list you paste is not sent anywhere.
- Rows read
- 17
- Unique values
- 16
- Extra duplicate rows
- 1
Problems found in 4 checks.
Duplicate serial numbers(1)
| Value | Count | Lines |
|---|---|---|
| SN000106 | 2 | 5, 6 |
Same number apart from leading zeros
No different spellings collide when read as numbers.
Format consistency
Length distribution
- 8: 15 (dominant)
- 7: 1
- 9: 1
Character pattern · A = letter, 9 = digit; other characters as they are.
- AA999999: 15 (dominant)
- AA99999: 1 · example: SN00114
- AA-999999: 1 · example: SN-000117
Rows that deviate from the dominant length or pattern (2)
- line 11: SN00114
- line 14: SN-000117
Character and length check
Leading or trailing whitespace (trimmed for the check) (1)
- line 12: SN000115␣
Consecutive ranges and gaps
Prefix: SN · 15 unique · Span 000101 – 000122
Coverage: 68.18% · Missing numbers: 7
Consecutive ranges (4)
000101 – 000103; 000105 – 000106; 000110 – 000116; 000120 – 000122
Gaps (missing numbers) (3)
000104; 000107 – 000109; 000117 – 000119
Prefix: SN- · 1 unique · Span 000117 – 000117
Coverage: 100% · Missing numbers: 0
Consecutive ranges (1)
000117
Duplicate = same value on several rows · range = prefix + trailing digit string, consecutive numbers under the same prefix · gap = missing numbers between two consecutive ranges · coverage = unique / (largest − smallest + 1)
The tool only examines the list you paste. A gap can mean the number was not printed, was scrapped or is on another list; check the reason for every gap against printer and line records. This tool is a preliminary check, not legal or technical advice.
Let's compare printer, camera and database records together to find where duplicate and missing numbers come from.
Request a conversation01
How to use it
A
Paste the serial numbers; if you pasted a table, set the column number and the header option.
B
Review the duplicates, format deviations, damaged characters and lost leading zeros.
C
Look at the consecutive ranges and gaps; copy the summary and compare it with the printer records.
02
What to look for in a serial number list
A duplicate serial number means two separate units of the same item received the same identity; when one code is read twice later, you cannot tell which is genuine. That is why a number list is scanned for duplicates before and after printing.
A serial number must be unique together with the GTIN it belongs to; the same serial number can legitimately repeat under different GTINs. This tool compares a single list, so paste the list of each GTIN separately.
03
Gaps and consecutive ranges
In a batch numbered sequentially the numbers run in consecutive blocks. A gap between two blocks shows that those numbers were not printed, were scrapped, went to another line or were transferred incompletely. A gap is not always an error but every gap should have an explanation.
The tool splits serial numbers into a prefix (the letter part) and a trailing digit string; it sorts the numbers under the same prefix and splits them into consecutive ranges. The coverage ratio shows how much of the numbers between the smallest and the largest is present in the list.
04
Format, character and spreadsheet problems
The GS1 application identifier (21) carries at most 20 characters and uses GS1 character set 82: digits, letters and some signs. Spaces and non-ASCII letters (such as ı, ş, ğ, İ) are not in this set and can cause problems in readers or systems.
Spreadsheet software can turn long digit strings into scientific notation (1.23E+12) and strips leading zeros; both errors silently lose numbers. The tool reports them separately. Keep the serial number column in text format in your spreadsheet.
FAQ
- Why is a duplicate serial number a problem?
- A serial number exists to identify a unit uniquely. The same number on two units leaves it unclear which unit is meant when it is read, and breaks traceability.
- Is a gap in the list always an error?
- No. The number may have been scrapped before printing, used on another line or reserved. What matters is that every gap can be explained with printer and line records.
- How does spreadsheet software damage my serial numbers?
- For values made of digits it strips leading zeros (000123 → 123) turns long numbers (in General format 12 digits and more) into scientific notation and zeroes the digits after the 15th. Set the column to text format and keep the values in quotes when exporting.
- Can serial numbers of different GTINs be checked together?
- They can, but the result would mislead: the same serial number can legitimately repeat under different GTINs. Paste the list of each GTIN separately.
- Is the list I paste sent anywhere?
- No. The check runs in your browser; the list is not transmitted to a server or stored.
Let's find where duplicate and missing numbers come from
We compare printer, camera and database records together and set up unique number allocation on the line.