Most barcode generators make you do one at a time, require signup for bulk, or upload your data to their servers.
This one: upload Excel/CSV, pick column, download ZIP (with 600 DPI). Everything runs in browser - your data never leaves your machine.
Handles the Excel leading-zero problem (UPCs starting with 0 stay intact).
Free, no limits. Might add print on demand integration features later if there's demand, or (API, more formats) - for now just seeing if people find it useful.