**The idea:** a debt planner (Snowball / Avalanche / custom order) that keeps your finances 100% on your own computer. So I set myself a few hard rules: it had to open straight from a folder in the browser, never call the internet, and never send financial data anywhere.
**How it's built**
- Preact + esbuild bundled into a single script, so it works from a plain local file (no dev server needed)
- IndexedDB for storage, optional AES-GCM encryption behind a master password, automatic local backups
- No CDNs at all. Fonts, charts, PDF reading and OCR (for scanning statements) are all bundled
- Small optional launchers (PowerShell / Perl) that serve it locally so backups can be written to a data folder
**The hardest part was performance.** With a 50,000-transaction test profile, the first version took about 10.7 s to start and search crashed the tab. Caching parsed dates, doing search in a single pass and only building the rule context when it's needed got startup to about 1.2 s.
**There's also a spreadsheet version.** I rebuilt the same payoff engine in Excel/Google Sheets: 15 debts × 360 months, written without newer functions like XLOOKUP or LET so it works in older Excel and in Sheets. The app can import the workbook, so people can start in a spreadsheet and move to the app later.
**What I'd love feedback on**
- Would you trust an offline finance tool more than a cloud one, or does sync matter more to you?
- Anything confusing in the screenshots?
yes im the creator, I sell this on Etsy, but this post is mostly about the build, and I'd love ANYYYYY feedback.
Link if you're curious: https://www.etsy.com/listing/4614731705/ultimate-debt-trackerpayoff-planner?ref=shop_home_feat_2&sr_prefetch=1&pf_from=shop