The generator above encodes data into a one-dimensional barcode as you type. It covers the eleven symbologies that account for nearly every linear barcode in retail, logistics, healthcare and industry, validates your input with character-level diagnostics, and exports print-ready PNG or vector SVG — all without a single network request.
What a barcode is
A 1D barcode is a row of bars and spaces of varying widths that a scanner reads left to right. The pattern is not a picture of the data; it is the data, expressed as a sequence of narrow and wide elements defined by the symbology’s specification. Where a QR code stores information along two dimensions, a linear barcode stores it along one — which keeps symbols short, cheap to print at small sizes, and universally readable by the simplest scanner hardware built in the last forty years.
Every symbology defines three things: an alphabet (which characters it can encode), an encoding table (how each character becomes bars and spaces), and a check digit rule (how the symbol proves it was scanned correctly). The generator implements all three faithfully for each of its eleven symbologies, and its encoding engine is verified pattern-for-pattern against the BWIPP reference implementation — the same engine the barcode industry uses to certify printers.
The eleven symbologies
Code 128 is the workhorse for logistics and shipping labels. It encodes the full ASCII set, switches between three subsets automatically to stay compact, and carries a mandatory mod-103 check digit. Code 39 is the classic industrial alphabet — digits, capital letters and seven symbols — still common on nameplates and in warehouses. Code 93 is Code 39’s denser sibling: full ASCII through shift characters, two mandatory check digits, and a smaller footprint.
EAN-13 and EAN-8 are the retail barcodes you see on nearly every product outside North America; UPC-A and UPC-E are their North American counterparts, with UPC-E compressing zero-heavy UPC-A numbers into roughly half the width. ITF-14 encodes 14-digit shipping container codes with interleaved pairs and the bearer bars the GS1 specification requires. Codabar lives in libraries and blood banks, MSI / Plessey in inventory shelves and point-of-sale add-ons, and Pharmacode packs a single number into the tiny symbol printed on pharmaceutical packaging to prove the packet passed through a packing line.
Check digits, computed and verified
A check digit is a final character computed from all the others. When a scanner reads a barcode, it recomputes that digit from what it actually saw; if the two disagree, the read is rejected instead of silently entering a wrong number into your inventory system. EAN, UPC and ITF-14 use weighted mod-10 sums, Code 128 uses mod 103, Code 93 carries two separate mod-47 digits, and MSI offers mod 10, mod 11 or compound variants.
The generator’s default mode computes the check digit for you: type the twelve digits of an EAN-13 and the thirteenth appears in the symbol automatically. Switch to verify mode and it validates the full number you supply instead, telling you exactly which digit it expected — useful when you are transcribing existing barcodes from packaging.
Quiet zones and sizing
The quiet zone is the empty margin on each side of the barcode. Scanners need it to find where the symbol starts and stops; the GS1 standard asks for ten modules (ten narrow-bar widths) on each side, and the generator warns you when you go below it. Bar width — the X dimension — sets the physical scale: every other measurement in the symbol, from wide bars to quiet zones, is a multiple of it. For screen use, a bar width of two pixels reads cleanly; for print, size the symbol so the final bar width lands above 0.25 mm and the height stays in proportion, or scanners aimed at an angle will lose the line they are tracing.
EAN-13, EAN-8, UPC-A and UPC-E get the classic retail text layout: digits printed under the bars, split around the guard bars, with the guard bars extended down through the text zone and the outer digits sitting in the quiet zones — exactly the geometry a checkout scanner expects.
Colors and scannability
Barcode scanners measure reflected light, not color. Dark bars on a light background give the strong reflectance contrast they need; the generator warns when your palette drops below safe contrast or inverts the polarity. Blue and green inks scan as dark, red as light — a red barcode on white will not scan at all. Keep bars black or dark blue on white or pale paper for anything that must be scanned by equipment you do not control.
Privacy: everything stays on your device
The encoding engine, the validation, the SVG construction and the PNG rasterization all run in your browser as plain JavaScript. Nothing you type is uploaded, logged or stored — close the tab and it is gone. There is no account, no rate limit and no service that could see your product numbers.
Exporting
PNG exports render at 1×, 2× or 4× the preview size with bars aligned to whole pixels so edges stay crisp, and SVG exports are true vectors that scale to any print size without blur. Both carry the human-readable text, guard bars and quiet zones exactly as previewed. Copy either format straight to the clipboard or download the file — the filename is derived from your data, locally.
Limitations
The generator produces linear (1D) symbologies; for two-dimensional codes use the QR Code Generator. EAN/UPC two- and five-digit add-ons, GS1-128 application-identifier parsing and rotated symbols are deliberately out of scope for this release. Code 128 supports ASCII 0–127; characters beyond that cannot be encoded in a single symbol without GS1 escape conventions.