In short
- Your Vocabulary Wallet, reviews and settings are stored in your browser.
- When you ask for a meaning, the word and the sentence around it are sent through Stemmy's server to our AI provider, Anthropic.
- X-Ray and Immersion send text from the page you are reading, and only when you start them.
- Cloud pronunciation runs when you press play, or for each new word if you turn on automatic pronunciation.
- When a word you saved appears on a page you read, Stemmy notes the site name on your device. This never leaves your device.
- We do not sell personal data or use your words for advertising.
What stays in your browser
The extension stores your Vocabulary Wallet (each saved word with its meaning, the sentence you found it in and the address of that page), your review progress and your settings in Chrome's extension storage on your computer. Page addresses are stored without the part after "?" or "#", which can contain sign-in tokens.
Seen again. When a word you already saved appears on a page you open, Stemmy keeps the site name (for example, nytimes.com) and a short snippet of the sentence, for up to ten such notes per word, so it can show you where you met the word again. These notes stay on your device: they are not synced and not sent to anyone. Stemmy does not keep a list of the pages you visit.
Timings that help diagnose slowness are kept only for the current browser session and are never sent.
Your account
AI features need a free account, created with Google Sign-In or with your email address. AI features need a free account (Google Sign-In or email). Each account gets 150 free AI uses in total, once; Ghost Card lookups and cloud voice draw on them. Accounts, sync and the count of AI uses are handled by Supabase, our database and authentication provider. Your account stores your email address and how you signed in.
What is sent, and to whom
Meanings, stories and word categories
When you ask for a meaning, the word and up to a few sentences around it are sent through Stemmy's server to Anthropic, which runs the Claude model that writes the meaning. AI Stories send the words a story is written from; organizing your wallet sends saved words and their meanings. Anthropic processes this text to return the result; see Anthropic's privacy policy.
X-Ray and Immersion
If you choose "Find hard words on this page" (X-Ray), up to about 3,000 characters of the visible page text are sent to find hard words. If you turn on the Immersion button in Settings and press it, up to about 8,000 characters of sentences from the page, with some of your saved words, are sent to find natural places for your words. Neither runs unless you start it.
Pronunciation
Cloud pronunciation sends the word to Mistral AI, which returns the audio. It runs when you press play, or the first time each word is shown if you turn on automatic pronunciation. Audio is cached on your device, and if cloud audio is not available, your browser's built-in voice is used instead, which does not involve our servers.
Wallet Letters (optional)
If you switch on Wallet Letters, emails built from your due words are sent through Resend, our email delivery provider, which receives your email address and the finished message. Story and news letters are written with Anthropic from the words and meanings in that letter. If you press "Yes, I remembered" or "No, I forgot" in a letter, that answer is stored with your account so your review schedule can use it. Consent, delivery, unsubscribe, bounce and complaint states are kept as needed to run the service and to honour unsubscribe requests.
What sync stores
Sync turns on when you sign in. Your saved words, their meanings, the sentence and page address you saved them from, your review progress and the number of times a word was seen are stored under your account, so they stay the same across the browsers you sign in to. The "seen again" notes described above are not synced. Words you saved before signing in stay only on that browser unless you choose to copy them into your account.
This website
The stemmy.app home page and guides use Microsoft Clarity to understand how visitors use the site, for example which sections they scroll to and where they click. Clarity sets cookies and processes this usage data on Microsoft's behalf; see the Microsoft Privacy Statement. Clarity loads only after you choose "Allow analytics" in the banner shown on your first visit; choosing "No thanks" keeps the site free of analytics, and you can change your choice from the "Analytics" link in the footer. The blog, this page and the pages that Wallet Letters link to never load Clarity.
On phones, the "Copy link" and "Share" buttons only copy or share the Chrome Web Store link from your device; this website does not collect anything when you use them. Links to the Chrome Web Store carry campaign tags so we can see which page a visit came from; they do not identify you.
What we do not do
- We do not keep a list of the pages you visit.
- We do not sell personal data.
- We do not use your words to build an advertising profile.
- We do not store API keys in the extension: AI requests go through Stemmy's server.
How long data is kept
Data in your browser stays until you delete it or remove the extension; removing the extension also removes its local storage. Synced data is kept under your account while your account exists; deleted words are removed from this browser's sync records after 30 days. Wallet Letters states are kept as needed to honour unsubscribe and suppression requests.
Export and deletion
You can export your whole wallet as a file at any time and import it again. You can delete individual words, or all of them, in the extension; when you are signed in, deletions also apply to your account and your other devices. Removing the extension deletes the data it stored in your browser.
To delete your account and the data synced under it, email us at the address below.
Contact
Questions or requests about your data: hello@stemmy.app.
Changes to this policy
When this policy changes, the date at the top of the page changes too.