What detection checks

The generator checks number patterns and check digits right in your browser.

• 1Z identifiers: 18-character 1Z format with its check digit.
• Numeric tracking formats: supported 12- and 15-digit formats, Ground 96, 34-digit formats and legacy ASTRA. Short numeric IDs overlap other numbering systems: they need review unless the pasted text provides matching context.
• Postal numeric formats: supported numeric 91–95 prefixes and lengths with a GS1 check digit, including supported 420 routing prefixes.
• International post: 13-character S10 format and check digit.
• Containers: supported identifiers are checked for format and length. Unverified formats remain review candidates.

Green: supported format/checks pass. Amber: possible match—review and select it yourself. Red: a supported check failed. When nothing matches, the generator says no recognized sequence was found. You can turn detection off to encode custom data.

Input and output

With detection on, the tool extracts supported complete sequences and ignores surrounding prose. It never slices a long uninterrupted number into shorter tracking IDs. With detection off, each line becomes one barcode; “Spaces separate barcodes” instead splits whitespace. Duplicate entries and leading zeros are kept. Printed spacing inside recognized IDs is normalized; identifier letters are uppercased for recognized postal/carrier formats. Custom input retains its case and internal spacing.

Switching the barcode format changes the rules. Some formats need a specific number of digits, standard prefixes or a set structure, so they cannot hold just any tracking number. Their standard check characters may be added by the encoder. “Use format example” loads an example for the selected format.

CSV and XLSX imports use your selected column A–J; XLSX uses the first worksheet. The limit is 2 MB per file and 100,000 characters per paste. Store identifiers as text in Excel: long numeric cells and leading zeros may already have been lost. Formula cells are skipped. XML entities (special character references) and linked spreadsheet tabs are not loaded.

PNG and SVG downloads include the recognition caption and the original input value below the barcode. The barcode itself contains the selected format's encoded data. Batch ZIP export is not currently available. Print at actual size and verify the result with your intended scanner.

Sources

• Postal barcode specification (DMM 204)
• Carrier formulas and reference fixtures
• bwip-js format catalog

Rules reviewed October 17, 2026. Third-party licences.