# FAQ

## General

### Is it really free?
Yes. MIT licensed, no sign-up, no hidden costs.

### Do I need to install anything?
No. Just open the site in a modern browser.

### Is my data safe?
All data stays in your browser's localStorage. Nothing is sent to external servers except API calls you explicitly trigger.

### Can I use it offline?
Yes. After the first visit, the Service Worker caches the site for offline use.

### Can I contribute?
Absolutely. See `CONTRIBUTING.md` in the repository root.

## Technical

### What browsers are supported?
Latest versions of Chrome, Firefox, Safari, and Edge.

### Does it work on mobile?
Yes, fully responsive.

### Why no React/Vue/Angular?
To keep the project simple, dependency-free, and deployable as pure static files. Vanilla JS is powerful enough for our needs.

### Can I self-host it?
Yes. Clone the repo and serve the root directory with any static file server.

## Modules

### How do I add a new module?
See the [Developer Guide](DeveloperGuide.md).

### Can I request a new module?
Open an issue on GitHub with the `enhancement` label.

### Are the calculations accurate?
Yes. All formulas are based on standard finance/accounting textbooks and verified.