Online notepad

The text is kept in your browser’s local storage, which is a per-site, per-device store the page can read and write without a server. That is the whole design, and both halves of it matter. Nothing is transmitted, so a note you would not put in someone else’s document is safe here. But equally nothing is synced — open the same page on your phone and it will be empty, because the two browsers have separate stores.

What clears it is worth knowing, because it will eventually happen. Clearing browsing data removes it. A private or incognito window keeps its own store and discards it when the window closes. Some browsers evict storage for sites you have not visited in a long time. And on iOS, Safari clears storage for sites unvisited for seven days. So this is right for a scratchpad and wrong for anything you cannot afford to lose — download the file if it matters.

Saving is deferred by a fraction of a second rather than run on every keystroke. Writing to local storage is synchronous, meaning it blocks the page while it happens, and on a document of a few thousand words doing that per character is felt as a stutter while typing.

There is a size ceiling of roughly five megabytes per site, shared with everything else this site stores. That is about two million characters — far more than anyone types into a scratchpad, but the page says so if the write is ever refused rather than silently losing your work.