Privacy Policy

Koi Karte is an app developed and operated by SOLVLET for keeping a record of each koi you own — where it came from, how it has grown, the care it has had, its show history and its photos, gathered into one record per fish.

This page describes what Koi Karte keeps about you, what it is used for, and where it is stored. It describes what the software actually does; nothing is collected that is not listed here.

Creating an account takes three things: an email address, a display name, and a password. The address is used to sign you in and to reach you (including the password-reset link you ask for); it is stored in lower case so that capitalisation cannot split one person into two accounts. The display name is what the app calls you — it does not have to be your real name. The password is stored only as a bcrypt hash. The plain text is kept nowhere, so nobody running this service can read your password.

We also ask, optionally, for your age range (six bands) and gender (three options). They are used only to understand who the app is for, so that it can be made better. Both start at “Prefer not to say”; if you leave them alone, nothing is stored for either.

On your first visit, and then as you sign up and use the app, we automatically record where your first visit came from (the referring site, the advertising parameters (UTM), and the first page you opened), your device type (one of three values only: phone, tablet or computer), the display language and time zone at sign-up, and when you last used the app. They tell us how people find Koi Karte, which screen widths and languages deserve the work, and whether people sign up and leave or keep using it.

A record of the first visit itself — at the same moment the referral above is noted in a cookie (kk_src), the same details (the host name of the referring site, the UTM values, the first page opened, the display language, the device category, and the date and time) are also written as a single row that belongs to nobody. It is tied neither to signing in nor to an account, and it holds neither your IP address nor the raw User-Agent string. It is there only to count how many people arrived from where, and it is deleted 400 days after it is written.

IP addresses are not stored in our database. The details your browser sends about itself (the User-Agent) are discarded the moment they are reduced to those three categories. No device name, no OS version.

We also record the milestones you hit inside the app — reaching the free plan’s limit, starting the subscription flow, having the Hobbyist plan become active — as the kind of event and the time it happened, nothing more. They tell us where people get stuck; none of what you typed is part of them.

Everything you write afterwards — a koi’s name, variety, breeder, region, bloodline, where you got it, what you paid, your notes, your ponds, measurements, care logs, show results, and the photos and certificate images you upload — is stored. Keeping that is what the app is for.

If you subscribe to the Hobbyist plan, we store the customer and subscription identifiers held at Stripe, the state of the subscription, and the end of the current billing period, so that the app can show which plan you are on and, after you cancel, how long you can keep using it. Only Stripe handles your card number; it never reaches us.

These are the cookies we use, and that is all of them. None of them are for advertising or analytics.

kk_session — keeps you signed in. It lasts 30 days, cannot be read by JavaScript (httpOnly), and is deleted the moment you sign out.

kk_src — a note of where your first visit came from. It lasts 30 days and is also httpOnly. It is written on your first visit only and never overwritten.

NEXT_LOCALE — remembers the language you chose. It is set automatically by the language-switching library (next-intl), and it disappears when you close your browser.

On your first visit we also read your browser’s language preference (the Accept-Language header) to decide which language to show. It is read, not stored.

What you entrust to us is used for running the service and for deciding how to improve it: showing you your records, keeping you signed in, handling the subscription you asked for, sending the messages you need such as a password reset, and understanding who uses the app and how.

What you entrust to us is never sold to anyone, and never handed over for advertising. There is no analytics SDK and no advertising tag, so opening a page sends nothing to an outside service.

If we change the price or the terms, we announce it on the terms page and by email at least 30 days in advance. Changes to this page are announced here.

The database and the servers that hold your records are in Render’s Singapore data centre. The photo and certificate image files themselves are stored in Cloudflare’s storage (R2), and the mail you send to our contact address is received through Cloudflare as well. What you entrust to us is therefore kept outside Japan.

For a Hobbyist subscription, your email address, display name, and your user number here (along with the language the payment screen is shown in) are passed to Stripe when you start the sign-up flow, and the receipt reaches that address from Stripe. Only Stripe handles your card number; it never reaches us.

Email delivery — a password reset, for instance — goes through Resend, and the recipient address and the text of that mail go to them. It goes there only so that the mail arrives; it is not used for advertising.

Beyond these, nothing you entrust to us goes anywhere else. All of them are used under terms that do not let them use the data for anything beyond that purpose.

All of them are based outside Japan. If you ask us at the contact address below, we will tell you without delay which country each one is in, what that country’s personal-data protection regime is, and what measures that company takes.

The photos and certificate images you upload are shown only to you, while signed in. Opening an image’s address as somebody else shows nothing.

An uploaded image is converted to a form the app can display (WebP) and resized before it is stored; the original file is not kept. That conversion strips the information embedded in the file — the time it was taken, the location, and the rest of the EXIF data.

A breeder or health certificate can show other people’s details — a breeder’s name, a previous owner’s name. Whether to upload such an image is your own responsibility. We use those images for nothing but showing them back to you.

Deleting a photo removes the stored image file itself, not just the row in the database.

Your koi, measurements, care logs, show history and ponds can be exported as CSV at any time and kept yourself. This works on the free plan too. Photos and certificate images are not included in the CSV — save those from the screen, one at a time.

For as long as your account exists, your records are kept. This is an app for looking back, and the oldest entries are the ones worth the most. When you sign out, the record of that session held on the server is deleted at the same time.

Koi, measurements, care logs, show results and photos can be deleted from the app at any time. To have everything removed along with the account, write to the address below from your registered email address, and we will delete the account together with its records and photos. If you are on the Hobbyist plan, the subscription is cancelled at the same time, and we do not refund the rest of the period you have paid for.

The records of what you paid — the invoices and the receipts — stay with Stripe for a period after you leave, because the law requires those books to be kept. A record that we sent you an email — the address and the time — stays with Resend for a while too.

For anything on this page, for questions about your own data, or to close your account and have it deleted, write to:

Write to this same address for our postal address and the name of the person responsible, and to ask us to disclose, correct, add to, delete, or stop using the personal data we hold about you, or to stop passing it to anyone else. Once we have confirmed that the request is yours, we act on it without delay.

hello@solvlet.app

If what we collect or what it is used for changes, this page is updated first and the date at the top moves forward. If a change works against you, we announce it here and by email at least 30 days beforehand. That date is how you can tell whether anything has changed.