Free Code 39 Extended Barcode Generator — Full ASCII, No Signup, Instant Download

Standard Code 39 encodes 43 characters: uppercase letters A–Z, digits 0–9, and eight special characters (space, -, ., $, /, +, %, *). Code 39 Extended — also called Code 39 Full ASCII — extends this to all 128 ASCII characters by encoding non-native characters as two-symbol sequences using the four shift characters ($, /, +, %). For example, lowercase 'a' is encoded as the two-character sequence '+A'. Physically, both variants use the same bar and space patterns; the difference is in how the scanner interprets multi-character sequences.

Code 39 Extended barcodes can be physically read by any Code 39 scanner. However, to decode extended characters — such as lowercase letters — correctly, the scanner must be explicitly configured for Code 39 Full ASCII mode. A scanner set to standard Code 39 mode will return the raw two-character shift sequences (e.g., '+A') rather than the decoded character ('a'). Check your scanner's programming manual or configuration sheet for the Code 39 Full ASCII enable code.

The Code 39 standard does not mandate a check digit, but an optional Mod 43 check character is widely supported. When used, the check digit is computed as the sum of all encoded character values modulo 43 and appended as the last data character before the stop symbol. Some regulated applications — including HIBC healthcare barcodes and certain aerospace standards — require the Mod 43 check digit. This generator computes and appends the check digit automatically when the option is enabled.

Code 39 Extended encodes all 128 ASCII characters: uppercase letters A–Z, lowercase letters a–z, digits 0–9, control characters (NUL through US and DEL), and all printable punctuation and special characters including @, #, !, (, ), [, ], {, }, \, ^, ~, and more. Characters are encoded either as single native Code 39 symbols (for the 43-character native set) or as two-symbol shift sequences (for all others).

Both Code 39 Extended and Code 128 can encode the full 128 ASCII character set. Code 128 is significantly more compact — it encodes each character in fewer modules, producing a narrower barcode for the same data. Code 128 also has mandatory check digit verification. Code 39 Extended is wider for the same data length, especially when many non-native characters are present (since each requires two symbols). Choose Code 39 Extended when your scanner infrastructure is already deployed for Code 39 and cannot be replaced; choose Code 128 for new deployments where barcode size or data density matters.

There is no fixed minimum or maximum data length specified by the standard, though practical implementations require at least one data character. The barcode width scales linearly with data length: native Code 39 characters each add one character width, while extended (two-symbol) characters each add two character widths plus an inter-character gap. There is no artificial data length limit in this generator. Very long strings or strings with many extended characters will produce wide barcodes — verify that the result fits your label dimensions using the live preview.

ISO/IEC 16388 requires a minimum quiet zone of 10 times the X-dimension (module width) on each side of a Code 39 or Code 39 Extended barcode, or a minimum of 2.54mm — whichever is greater. The quiet zone is the blank space to the left and right of the barcode that allows the scanner to detect the start and stop of the symbol. This generator automatically includes correct quiet zones at the default width and allows you to increase them through the margin setting.

Yes. All Code 39 Extended encoding is performed entirely in your browser using client-side JavaScript. Your input data — including any asset IDs, patient identifiers, document codes, or proprietary part numbers — is never transmitted to any server and never stored or logged anywhere. Close the browser tab and all data is gone. This tool is safe to use with sensitive or confidential identifiers.