Browser-only tools: what stays on your device

A name changes into decorative lettering as you type. A date becomes a Japanese era year before you press a submit button. Neither interaction needs an account, but that alone tells you little about where the input goes. A site can send text to a server without asking you to sign in. The useful question is narrower: does this particular calculation or transformation need to send its input anywhere?

In our current Symbol Copy and Kurashi Tools implementations, the transformations and calculations run in JavaScript on your device. They do not call a calculation or text-generation API with your input. That is a description of the tool operation, not a promise that the whole website makes no network requests, stores nothing, or protects information after you deliberately share it.

Downloading the tool is different from submitting an answer

Opening a website first downloads a document and resources such as styles, fonts, and JavaScript. Those requests reach the hosting service. Once the code has arrived, it can perform work locally. For example, Symbol Copy maps ordinary letters to other Unicode characters using data included with the site. Changing the input does not require a server to choose the replacement characters.

This distinction matters when a network panel looks busy. A downloaded font is not evidence that your nickname was uploaded. Conversely, an attractive interface or a quick response is not evidence of local processing. What matters is the request's destination and contents, and whether your test input appears in it. Treat the label “browser-only” as a claim you can examine, not a substitute for that examination.

Try a small check with fictional text

You can inspect an ordinary browser session without putting real personal information into a test. Start with the Fancy Text Generator and use a distinctive fictional string such as moss-lantern-482. Do not use a password, private message, or actual birthday. The Chrome network-panel guide explains the controls used below; names may differ in other browsers.

1. Open the tool, then open Developer Tools and choose the Network panel.
2. Reload once with the panel open so you can see the initial resource downloads.
3. Wait for loading to settle, remove any request filter, and clear the recorded list.
4. Type the fictional string, change it, and inspect the displayed results.
5. Examine any new requests, including their URL, query parameters, and request payload where available.
6. If you test Copy too, inspect that action separately from typing. Do not click an advertisement.

The transformation should not need a request carrying that string to produce its result. If you see requests, identify them before drawing a conclusion. An analytics event, a resource download, and a request to calculate an answer are different things. Looking only at Fetch/XHR can also miss other traffic; start with the complete list.

This is a check of one page, action, browser, and version. It is not a formal security audit. A clear log does not prove what every browser extension does, what a different page sends, or what future code will do. If something looks inconsistent, report the page and action using a fictional example rather than forwarding a log containing personal data.

Local storage is still storage

Symbol Copy's recent copies and favorites are saved in browser storage. Kurashi can remember a birth date for use across its own tools. “No account” therefore does not mean “nothing is remembered.” Someone returning to the same browser profile may see information you left there, even though it was not saved to a GreedMonster account.

MDN describes localStorage as storage associated with a site's origin that can persist across browser sessions. It is not automatically shared between our two service subdomains. Closing a normal tab does not necessarily remove it. Browser privacy settings can restrict it, and private-browsing storage has a different lifetime. We do not treat browser storage as a permanent backup.

The current Symbol Copy storage code keeps bounded recent and favorite lists, not an unlimited archive. Use the site's clearing controls when you are finished on a shared device. If you clear storage through your browser, check which site's data you are removing; clearing unrelated sites is unnecessary.

A shared URL changes the boundary

Some Kurashi tools offer an explicit result-sharing action. That action can put selected inputs, including a birth date, into the query part of a URL. The sharing implementation makes that link for you. It is different from silently uploading each keystroke, but the resulting link is not private merely because the calculation was local.

Anyone receiving the link can read its parameters. Opening it sends its path and query to the hosting service as part of the page request. Copying it into a message also gives that messaging service the link. Our analytics URL filter removes queries and fragments from the events it handles; it cannot undo a URL you chose to distribute or remove information from every other system involved.

Before sharing, inspect the address. If it contains personal information, share a non-personal result in ordinary text instead, or use a fictional input. Never rely on a shortened URL to make the underlying information confidential. The important boundary is your deliberate decision to send the information, not whether the earlier arithmetic happened in a browser.

Advertising and analytics are separate operations

The services use Vercel Web Analytics, and Kurashi includes an AdSense script. Those systems can make their own requests even when the tool needs no calculation server. A copy or calculation event is not the same as sending its contents: our event handlers use tool or style identifiers rather than the input text. Nevertheless, network inspection should include these requests rather than pretending they cannot exist.

For the current service-specific details, read Symbol Copy's privacy notice or Kurashi's English privacy notice. The useful promise is limited and testable: the core tool processes input locally. Storage, sharing, hosting, advertising, and measurement each deserve their own question.

Local processing also does not guarantee a correct answer. Our calculation correction note explains the separate question of how a result is checked.