Browsers can remember small pieces of data for a site. localStorage is one of those slots: key–value strings kept on the device, scoped to the site’s origin (scheme + host + port). It is not a password vault, and it is not automatically emptied when you close the tab.
localStorage vs cookies: Cookies can be sent with HTTP requests. localStorage is not attached to every request by default. localStorage can be read by JavaScript on that origin. Cookies can too, unless they are marked HttpOnly.
What localStorage is for
Typical uses: a saved theme preference, To-Do List tasks, and saved invoice company defaults. ToolsTask uses it for theme preference, the to-do list, and Invoice Generator seller/company defaults — on your device, under this site’s origin. Clearing site data in the browser removes it.
How long it lasts
There is no expiry field. Data stays until the site deletes the key, you clear storage, or you use another browser profile. sessionStorage is similar but clears when that tab’s session ends. IndexedDB is for larger structured data; calculators on this site do not need it.
Privacy in practice
Because localStorage stays on the machine, another person with access to your logged-in OS account and browser profile can open DevTools and read it. It is the wrong place for passwords, card numbers, or health records. A shared family computer is a shared drawer.
localStorage does not replace the rest of the site’s network behavior. ToolsTask still uses Google Analytics on pages, and the Contact form sends a message through Web3Forms if you submit it. Calculator inputs are not the contact form. Details are in the Privacy Policy.
How to inspect or delete it
- Open the site, then DevTools (often F12).
- Application (Chrome/Edge) or Storage (Firefox) → Local Storage → the origin.
- Delete keys, or use the browser’s “clear data for this site” control.
Private/incognito windows often isolate or discard this storage when the window closes — convenient for a one-off calculation, useless if you wanted a to-do list to persist.
Practical habits
- Do not paste secrets into any web tool you would not write on a sticky note on the monitor.
- Export anything important (an invoice PDF) rather than trusting the browser as backup.
- On a public PC, use a private window and close it when finished.
See a tool that can save locally
The to-do list stores tasks in the browser. The invoice generator can save seller/company defaults there; it does not keep a complete invoice backup. Treat them as device-local notes, not cloud accounts.
Open To-Do List →What this site stores versus what it sends
Theme keys and some drafts live in localStorage. Google Analytics, when the page includes it, uses its own cookies and network calls to measure traffic. Submitting Contact sends the fields you typed through Web3Forms. Those are three different pipes. Clearing localStorage does not opt you out of Analytics; using a form is a choice to send a message.
A password generated in the tab is not written to localStorage by the generator pages. If you paste it into the to-do list, that is you storing it — do not do that.
Takeaway
localStorage is convenient, origin-scoped, and visible to scripts and to anyone who uses your browser profile. Use it for preferences and drafts; keep secrets out of it; remember analytics and contact forms are separate channels.