Privacy Policy

Kitsumi browser extension Last updated: 11 November 2026

The extension has no accounts and no analytics. Everything it stores, it stores in your own browser. The developer runs one server, the Kitsumi Vault subtitle library, and the extension asks it for subtitles only when you switch the Vault on. It makes network requests only when you use a feature that needs one, or to show this month's support total on the occasional support reminder, and every one of those is listed below.

On a fresh install, nothing you type, hover, watch or listen to is sent anywhere. The features that would send something are off until you turn them on.

The Chrome Web Store asks every developer to tick which categories of user data their extension handles. Google defines handling as "collecting, transmitting, using, or sharing", and requires the declaration "even when data is processed or stored locally on a user's device and is not transmitted to external servers or third parties".

That is a much wider word than most people read into it. Reading the subtitle line on your screen in order to draw it back with a dictionary attached is handling, even though the line never goes anywhere. Kitsumi ticks the categories honestly rather than picking the flattering reading, so here is what each one actually is:

• Website content. The subtitle text on the page, read so the overlay can be drawn and so you can hover a word. That reading happens on your device. Two optional features then send a piece of it onward, and only the piece you asked about: online dictionary lookups send the word you hovered to the dictionary service (and, when you click the star to explain a line, that line and each of its words), and the AI features send the subtitle line, or the audio of the video, to the provider whose key you entered. Both are off until you switch them on, and both go to those services rather than to anything of Kitsumi's.
• Authentication information. The API keys you choose to type in, for Jimaku, OpenSubtitles, SubDL, Groq, OpenAI, Google Gemini, OpenRouter, WaveSpeed, KRDict or DeepL. They sit in your browser and go only to the service that issued them.
• Personally identifiable information. Only the email you may type in for MyMemory (Dict tab -> Keys, optional), which raises MyMemory's free daily limit. It sits in your browser and goes only to MyMemory, with its requests.
• Web browsing activity. The title and address of the tab you are watching, used to work out which show it is, and remembered per show so the next episode finds its subtitles. It is sent to a subtitle provider only on the sites you have put on your list, and only after you have accepted the providers notice inside the extension (see below).

None of it is collected by the developer. The extension has no account, no analytics and no telemetry. The one server of the developer's it can ask for subtitles, the Kitsumi Vault, receives only the search described below, and only when you have switched the Vault on. Those categories describe what the software touches on your machine, not what anybody collects about you. Everything below sets out exactly where each thing goes.

All of the following is kept locally in your browser, using extension storage and IndexedDB. None of it is transmitted anywhere.

• Your settings: subtitle appearance, position, timing offsets, per-show sync offsets, interface preferences, allowlisted sites.
• Your study data: words you have looked up, words marked as known, study time, streaks, active days, ranks and achievements, per-language statistics.
• A safety copy of your settings and study data, made once a day and kept for 3 days, so they can be restored if the browser loses them. It has no API keys, and it is removed with the extension.
• Dictionaries you install, stored as local databases.
• Fonts you download or add for subtitles, and word packs you download for Advanced scanning, also stored as local databases.
• Subtitle files you load, for the duration of playback.
• Recognition data for any OCR language you have used, cached after its first download.
• API keys you choose to enter for optional third-party services.

You can delete all of it at any time by removing the extension, or by using the reset controls in the extension's settings.

Subtitles you save from the subtitle timeline (the 📥 button, as .srt or plain text) are handed to your browser as an ordinary download: a file on your computer, which Kitsumi does not keep a copy of or send anywhere.

Apart from the support total and the optional Kitsumi Vault (both below), Kitsumi contacts only third-party services, and only in response to an action you take:

Online dictionary lookups are off on a fresh install. Until you switch them on, every lookup is answered from the dictionaries stored on your device, with no network request at all. You can turn them on in the popup, from the Dict tab or the switch on its main screen; the first time, Kitsumi shows a short notice saying exactly what is sent and to whom, and nothing is sent before you accept it. Turning every source off again switches them back off.

Custom subtitle providers are yours, not Kitsumi's. In Settings, Subtitle providers, you can add a subtitle site Kitsumi does not support (advanced). Kitsumi shows three warnings first and adds nothing until you pass all three; it records on your device when you accepted them. A custom provider only ever talks to the one site you confirmed, and only over https; your key goes to that site and nowhere else, and a request carrying it is never followed to another address. What comes back is limited to titles, ids and file names as plain text, and subtitle files that really are subtitles (anything else is refused, and web code in them is removed). Everything that site receives or does is between you and it; see the licence.

Subtitle providers need a key of your own. Kitsumi ships no shared key. Jimaku, OpenSubtitles and SubDL each stay dormant until you enter one, so none of them is contacted until you decide to set it up. The Kitsumi Vault needs no key; it stays off until you switch it on.

Subtitle providers are asked only on sites you list. The automatic search (in the background, and the one that runs when you open Kitsumi) is built from the page's title and address, so it runs only on the sites you have added to your list in the extension. On every other site nothing is sent to any provider. The title is the page's own title (cleaned of the site name); on rare pages a site puts other text there too, such as a user name or a message preview, and that would go with it. To search only with what you type, turn off "Auto-search subtitles from page title" (and leave "Auto-load subtitles without opening popup" off). The first time you enable a provider, turn on the background search, or search by hand, Kitsumi shows a short notice saying exactly this and asks you to accept it; nothing is sent to a provider before you do. Declining switches the providers off again. Your list stays empty until you accept the notice, and YouTube is never on it: there Kitsumi uses YouTube's own subtitle tracks and asks no provider. Text you type into boxes on a page (search boxes, forms, messages) is not looked up: hovering or clicking skips them always, and selecting or right-clicking skips them too unless you turn off "Skip text fields" (article reader settings). Password and payment fields are never read.

The AI features are off by default and stay dormant until you enter your own API key. With no key present, no request is made to Groq, OpenAI, Google Gemini, OpenRouter or WaveSpeed at any time.

About the OCR download. Japanese vertical recognition works entirely offline; its data ships inside the extension. Any other language downloads its recognition data once, from tessdata.projectnaptha.com, and keeps it on your device afterwards. The only thing sent is the name of the language. In the Opera version of Kitsumi this also applies to Japanese, because Opera's store does not accept that file type in a package. What is downloaded is recognition data, not program code, and none of your images or text is uploaded for it.

Each third-party service handles the data it receives under its own privacy policy. If you enable one of these features, you are choosing to send that content to that provider, under your own account where a key is involved.

Kitsumi shows optional donation options: Patreon, a Monobank Jar, Ko-fi, and crypto addresses (USDT, USDC, BTC, ETH, XMR, SOL, LTC). Donating unlocks nothing.

Showing them sends nothing. A link opens that service's own page in a new tab, and its own terms and privacy policy apply there. The addresses and QR codes ship inside the extension, and Copy address puts the address on your clipboard.

Kitsumi does not see your payment, card details or wallet. Most blockchains are public, so anyone can see a transaction to these addresses, including the developer. Only the support total above is fetched, and that request says nothing about you.

Kitsumi requests access to all sites because subtitles have to be rendered over video players it cannot know about in advance, including players inside embedded frames. It reads the page only to find the video player and its subtitle track, the word under your cursor on a site where you turned the article reader on (it runs only on sites you add yourself), and any image you point the OCR at. On YouTube (and wherever Kitsumi shows subtitles) the subtitle text itself is read so its words can be hovered and looked up - with no site to add, since that is the overlay. The rest of the page, such as titles or comments, is read only where you added the site to the article reader.

Reading the page is how the overlay gets drawn, and it is why the store listing declares website content. What Kitsumi does not do is keep any of it or send it away. Page content is read, used to render the thing you are looking at, and discarded; nothing about the pages you visit is stored beyond the show title Kitsumi remembers so the next episode finds its subtitles.

There are two exceptions, both entirely in your hands and both off until you switch them on:

• Online dictionary lookups send the word you hovered to the dictionary service you picked, because that is the only way it can look the word up. When you click the star on a subtitle to explain the whole line, each word of that line is looked up the same way, and the line itself goes to MyMemory for a translation - only if MyMemory is one of your online dictionaries. If you enter an email in the Dict tab (MyMemory email, optional), it is sent to MyMemory with each MyMemory request, which gives a higher free daily limit; it is kept only in your browser and sent nowhere else. Kitsumi asks before you type it the first time. If you enter your own DeepL API key (optional), the line you explain can go to DeepL with that key for its translation, in the order you choose (by default only when MyMemory's daily limit is used up); the key is kept only in your browser.
• The AI features send the subtitle line, or the audio of the video you asked to transcribe, to the provider whose API key you entered.

Nothing else from the page is ever transmitted, and none of it is ever stored outside your browser.

If you would rather narrow this, both browsers let you restrict an extension to specific sites:

• Chrome: right-click the extension icon, "This can read and change site data", "On specific sites".
• Firefox: Add-ons Manager, Kitsumi, Permissions.

All features continue to work on the sites you allow.

• No user accounts, sign-in, or registration.
• No analytics, telemetry, crash reporting, or usage tracking.
• No advertising and no advertising identifiers.
• No cookies. Kitsumi neither sets nor reads any. When it loads a caption file or an image from the site you are on, your browser sends that site's own cookies with the request, as it does for the page itself.
• No selling or sharing of data.
• No transmission of your study history, vocabulary, or statistics anywhere.
• No sending of your API keys to anyone but the service that issued them.
• No looking up what you type into pages: text boxes are skipped by default (the "Skip text fields" switch), and password and payment fields always.
• No contacting a subtitle provider on a site you have not listed, or before you have accepted the providers notice.

Everything above is about the extension. The website where this policy is published, kitsumi.org, is hosted on Cloudflare Workers:

• It sets no cookies, has no accounts, and shows no advertising. Its fonts and scripts come from kitsumi.org itself (no Google Fonts or other font services).
• Cloudflare, as the host, processes visitors' IP addresses and request data to deliver the pages and to protect the site from attacks, under Cloudflare's own privacy policy: https://www.cloudflare.com/privacypolicy/
• The site counts visits with Cloudflare Web Analytics. It uses no cookies and no fingerprinting; it records the page visited, the referring site, the browser type and how fast the page loaded, and reports them only as totals. Nothing it records is used to identify you.
• Download counter: when you download a PDF from the site, a Cloudflare D1 table adds 1 to that file's total - the table holds only the file name and its count. To avoid counting the same download twice, a Cloudflare rate limiter looks at your IP address together with the file name for one minute. Kitsumi does not store your IP address, and no record is kept per person.
• Settings the site remembers stay in your browser and are never sent anywhere: in localStorage the colour theme (k-theme), the page language (k-lang) and a dismissed hint (k-coach); in sessionStorage the lighter animations choice (k-lite) and the scroll position of each page.
• Videos: the home page and /videos show a thumbnail only. The YouTube player (youtube-nocookie.com) loads only after you press play; from then on YouTube's and Google's privacy policies apply.
• Donations (/support): the links to Patreon and Monobank open their own pages, where their terms and privacy policies apply. The site never receives card details. Those services may show the developer your name and message. If you donate in cryptocurrency, the transaction is public on its blockchain.
• Links to the Chrome Web Store, Firefox Add-ons, GitHub, Discord and social sites are ordinary links: nothing loads from them until you click one.

The Vault is the developer's subtitle library, hosted on Cloudflare Workers (Cloudflare's privacy policy applies to the hosting: https://www.cloudflare.com/privacypolicy/). Using its subtitles in the extension needs no account (see the table above). Sharing subtitles on vault.kitsumi.org does:

• Sign-in: you type your email and receive a 6-digit code. The email is sent through Resend (EU region, https://resend.com/legal/privacy-policy) to deliver the code. The Vault keeps only a keyed hash of the address, never the address itself, so it cannot email you or show your address to anyone.
• Robot check: the sign-in and change-email forms load Cloudflare Turnstile (https://www.cloudflare.com/turnstile-privacy-policy/), which looks at your browser and connection to tell people from bots before a code is sent. It runs only on those forms, not in the extension.
• Supporter badges: once a day the Vault gets the developer's active Patreon patrons (https://www.patreon.com/policy/privacy) at $50 a month or more - their email and monthly amount - through the developer's own site olexify.dev, which reads them from Patreon (a private, key-protected request; nothing is cached or logged). Each address is turned into the same keyed hash sign-in uses and compared with the accounts; the addresses are not stored. A Vault account with the same email as a patron at $50 a month or more shows a badge (Legendary Lion, Half King or Lionheart) next to its name while the support lasts.
• Stored with your account: the name you choose to show with your subtitles, when you joined, your uploads, your votes and your reports, and any warning a moderator gave you. Your uploads and that name are public.
• Public profile: your username (unique; a moderator can replace an offensive one), the avatar you pick (an emoji or a colour - nothing is uploaded), when you joined, and counts of what you shared (sets, episodes, shows, upvotes received) are shown on your profile page and the People page's leaderboard. Votes you cast stay private.
• Your sign-in stays in that browser (localStorage); the server keeps only a hash of it, for up to 10 browsers.
• Limits: to stop abuse, a keyed hash of your IP address and of your email is kept with a counter for up to about 2 days. Nothing else about your device is stored, and the Vault sets no cookies and has no analytics or advertising.
• Takedown requests (vault.kitsumi.org/takedown): the name, email, organisation and signature you enter are stored as written, so the request can be handled and answered.
• On vault.kitsumi.org/account you can change your name and email, fix or delete the sets you shared, sign out everywhere and delete the account (your sets are deleted; the shows you added and the votes you cast stay, with no name on them).

Kitsumi is a general-purpose study tool and does not knowingly collect data from anyone, including children.

Material changes to this policy will be published at kitsumi.org/privacy and in the project's repository, and its "last updated" date will change. The version history is public in the repository.

Questions about this policy: olexifyyy@gmail.com Or ask in the Discord.