Privacy policy

Applies to the Sumico browser extension and the Sumico desktop app. Last updated 23 September 2026.

Sumico has no account, no sign-in and no server of its own. What you type stays in your browser on your device. The only thing that ever leaves it is a three letter currency code, sent to fetch an exchange rate.

What Sumico stores, and where

Everything Sumico keeps is written to your own device, in the browser profile the extension runs in, using IndexedDB. Nothing is uploaded, and there is no sync between devices.

• Your documents: the text you type and its title.
• Your preferences: theme, precision, thousands separator, base currency, angle unit, locale, rate source and font size.
• Session state: which document was open last, so it reopens where you left it.
• A cache of exchange rates, with the time they were fetched.

What Sumico sends

Exchange rates, and nothing else. Sumico requests them from three services, and which of them is used depends on your settings and on what your document mentions:

• open.er-api.com - daily rates for national currencies. This is the default source.
• api.frankfurter.dev - European Central Bank reference rates, used instead of the above if you select it in Preferences.
• api.coingecko.com - cryptocurrency prices, requested only when a line in your document mentions a crypto ticker such as BTC or ETH.

Each request carries the three letter code of your base currency, and for the crypto service also the tickers your document uses. It carries nothing else: not your text, not your document titles, not an identifier, not your browsing history. Rates are requested when Sumico starts and about every six hours after that, plus whenever you change the rate source or the base currency, or press Refresh rates now.

As with any request to any website, the service receiving it can see the network address it came from, and may log it under its own policy. Their policies: ExchangeRate-API, Frankfurter, CoinGecko.

Sumico also ships with a dated snapshot of rates inside the extension, so currency lines still resolve with no connection at all. When a rate is older than Sumico considers current, it marks it as stale rather than pretending otherwise.

What Sumico does not do

• No analytics, no telemetry, no crash reporting, no advertising and no third-party trackers.
• No account, no sign-in, no sync, no cloud storage.
• No AI and no API keys. Calculation happens on your device.
• No reading of the pages you visit. Sumico has no content scripts and no access to any website.
• No selling of personal data, no transfer of it to anyone, and no use of it for anything beyond the calculator itself.

Browser permissions

The extension asks for one Chrome permission, sidePanel, so that clicking the toolbar icon opens Sumico in the side panel. That is the whole interface.

It also declares the three addresses listed above as host permissions. They exist solely so the extension may request exchange rates from those three services, and they grant no access to any other site.

Keeping and deleting your data

Your documents stay until you delete them, inside Sumico or by clearing the browser data for the extension. Removing the extension removes its stored data with it. Because nothing is uploaded, there is no copy elsewhere for anyone to delete, and no request you need to send to have one removed.

Children

Sumico is a calculator. It is not directed at children, and it collects no personal information from anyone, of any age.

Changes

If what Sumico stores or requests changes, this page changes with it, and the date at the top moves. Substantive changes will be reflected in the extension's store listing as well.

Contact

Sumico is made by Maksim Golub. Questions about this policy: mak.golub@gmail.com. General help lives on the support page.