Cross-post notice: this is the canonical version. Reposts on Medium, Hashnode, and Indie Hackers will link back here. A few months ago I shipped a free invoice generator. The kind of tool freelancers find at 11pm when a client wants an invoice and they don't want to register on a CRM just to send a PDF. The whole product runs under four hard constraints I refused to break: 100% online — open the URL, use it. No install, no desktop app, no browser extension. Works on any laptop, tablet, or phone with a browser. Unlimited use — no per-invoice cap, no "after 5 invoices please sign up," no monthly quota. Generate one a day, generate a hundred a day. Same tool either way. No login — anonymous by default. No email capture, no account creation, no password reset flows, no session cookies tied to identity. Your data lives in your browser's localStorage; close the tab and nothing is sent anywhere we don't show you. Free, period — no paid tier, no credit card, no "premium templates," no watermark on PDFs.…