I needed to send an invoice maybe four times a year, and every option wanted an account and a monthly subscription. So I tried to see how far one file could go. This is the whole thing: one HTML file, 52KB. No build step, no dependencies, no CDN, no backend. Save it to your desktop, turn off your wifi, and it still works — there is nothing to sync because there is nowhere to sync to. The parts that took longest were not the ones I expected. Due dates were computing a day early for anyone east of UTC, because I had turned a calendar date into an instant. Money had to be rounded per line and then summed, not summed and then rounded, or the total disagreed with the printed rows by a cent. And getting a browser to emit a real A4 page instead of 1.5 pages took longer than the entire form did. If you would rather not trust me on the arithmetic, add #selftest to the URL and it runs 26 assertions in front of you. It is free and unlicensed, source is on GitHub. I would like to know where it breaks — especially the print output on browsers I could not test.

Offline Invoice

An entire invoice generator in one 57KB HTML file

An entire invoice generator in one 57KB HTML file