Kern privacy policy

Last updated 17 October 2026

Kern is a to-do app for iPhone and Mac. This page says what Kern keeps, who handles it, and how to delete it. In short: your tasks are used only to make Kern work for you. Nothing is sold, and nothing is used for ads or tracking.

Who is responsible

Mielmpie B.V., Amsterdam, the Netherlands (KvK 76751619). For questions or requests, write to hi@kern.do.

What Kern keeps

On Kern's server, linked to your account:

• Your email address, to sign you in.
• Your tasks and everything in them: titles, notes, dates, reminders, labels, spaces and sections, links between tasks, and the Activity log of who changed what and when.
• What you said or typed when you added a task, including the written-out words of a voice capture.
• The history of every change, which is how your devices stay in sync.
• What Kern's AI adds: where to file a task, research notes with their sources, the line under a task's title saying how to get it done, the buttons under its notes (such as "Track package"), short descriptions of your spaces, sections and labels, and the "About you" profile described below.
• When you add a task on the Mac with the window in front attached: the window's link (a web address, a Mail message, or a document on your Mac) as a button, and what the AI read in the window as part of the task.
• Your iPhone's push address, so Kern can tell it quietly that something changed. These pushes carry no task and no text.
• Small counters that limit how often the AI features run each hour or day.

Only on your device:

• Voice recordings, on your iPhone or Mac. A recording stays on the device until it has been turned into words, then it is deleted. It is sent to the transcription service and never stored on Kern's server.
• Your app preferences.

Who handles it, and why

• Supabase hosts Kern's database, sign-in and server functions, in Ireland (EU), and sends the sign-in emails.
• OpenAI turns voice recordings into words. It receives the recording and the names of your spaces and labels, so they are spelled right.
• Anthropic (the maker of Claude) runs Kern's AI features: filing what you captured into a task, editing a task by voice, researching a task (including web searches run by Anthropic), writing the line under each open task, finding the buttons under its notes, reading a window you attached on the Mac, and writing the descriptions and the About you profile. Each time it receives only the text that feature needs, such as the task's title and notes, for filing the names and descriptions of your spaces and labels, and for research the About you profile.
• On the Mac, when you press Tab to attach the window in front to a new task, Kern sends one picture of that window, with the app's name and the window's title, to Anthropic, whose AI reads what the window is about. Nothing is sent until you press Tab, and the picture is not kept by Kern, on your Mac or on its server.
• Apple delivers the quiet pushes to your iPhone; they carry no task and no text.
• Sentry receives the apps' crash reports, and PostHog their usage statistics, both in Germany (EU). Neither receives your tasks, your email address or your account; see below.
• Vercel hosts this website, and Cloudflare runs the kern.do domain and forwards email sent to hi@kern.do. Neither receives your tasks.

OpenAI and Anthropic process this data in the United States, under their terms for business customers, which do not allow them to train their models on it. They may keep it for a limited time under their own policies, for example to detect abuse.

Crash reports and usage statistics

When the iPhone or Mac app crashes, freezes or hits an error, it sends a crash report to Sentry: where in Kern's code it went wrong, the app and system version, and the kind of phone or Mac. A crash report leaves out your tasks, what you said, your email address and your internet address, and it is not linked to your account: a random number the app makes tells one copy of Kern from another. One exception on the Mac: when the app itself crashes, the report can include a snapshot of its memory at that moment, which may hold what was on screen; Sentry reads it to find where Kern crashed and then throws it away. Crash reports are always on, because they are how bugs get found and fixed (Kern's legitimate interest under the GDPR); you can object at hi@kern.do.

While Settings › Share usage statistics is on, the app also sends PostHog a count of moments such as "app opened", "capture saved" or "task completed", with their kind (voice or typed, which list) and whole numbers (how many tasks). Never a task's words, the names of your spaces, sections or labels, your email address or your account. PostHog is told to throw away your internet address and not to work out where you are, and a random number the app makes ties the counts from one copy of Kern together. The switch is on until you turn it off; once it is off, Kern stops counting.

Sentry keeps crash reports for 30 days, PostHog keeps the counts for a year.

The About you profile

To make research fit you, Kern writes a short sketch of you from your tasks: where you live, what you do, what you use and prefer. It leaves out health details, finances, exact addresses and anything about other people beyond a first name. You can read and edit it in Settings, under Research. Turning research off there stops Kern from researching tasks and from updating the profile.

What Kern never does

Kern shows no ads, does not follow you across other apps or websites, and does not sell or share your data with anyone beyond the services above. Its usage statistics count what is used inside Kern, never what your tasks say.

Claude's connector

You can connect Kern to Claude, for example in claude.ai or Claude Code. Once connected, Claude can read and change everything in your Kern (tasks, notes, Activity, research, spaces and labels) when you ask it to, and every change it makes is logged in the task's Activity. What Claude reads is handled by Anthropic under your own agreement with Anthropic. You can disconnect Kern in Claude's settings at any time, and deleting your Kern account ends the connection.

How long Kern keeps it

For as long as you have an account. Tasks you delete go to the Trash and leave your iPhone after 30 days, but Kern's server keeps them, with the history of changes, until you delete your account.

Supabase keeps technical logs of requests to Kern's server (the time, your account's number, your internet address and which function ran; never your tasks) for 7 days.

Deleting your account

In the app, go to Settings and tap Delete Account. Your account and everything listed above are deleted from Kern's server straight away, and the app on your iPhone is emptied. Copies in the hosting provider's daily backups expire within 7 days. Crash reports and usage statistics are not linked to your account, so they expire on their own (see above), and the app starts a new random number. You can also ask by email at hi@kern.do.

Your rights

Kern uses your data to provide the app you signed up for. Under European privacy law (the GDPR) you can ask for a copy of your data, have it corrected or deleted, or object to how it is used: write to hi@kern.do. For a copy of everything Kern holds about you, in one file: on iPhone, Settings › Export My Data; on the Mac, File › Export My Data…. You can also complain to the Dutch data protection authority, the Autoriteit Persoonsgegevens.

Children

Kern is not meant for children under 16.

Changes

When this policy changes, the new version appears on this page with a new date.