Barcode Generator

EAN-13 only for now — Code128 needs a ~107-symbol bar-width lookup table, and transcribing that from memory carries real risk of a subtle, hard-to-notice error (unlike EAN-13's much smaller, well-documented digit tables). Rather than ship a Code128 encoder we can't be confident is byte-for-byte correct, we're leaving it out until it can be built against an authoritative reference.
Please scan-test a generated barcode with a real scanner/phone app before relying on it — as with the QR Code Generator, static review can't confirm the actual bar pattern scans correctly.