What an input method actually is
Every Android keyboard can read what you type. Not because of a flaw, but because that is what an input method is: the system hands it your keystrokes so it can put characters on screen, correct typos and suggest the next word.
That includes ours. LocalType reads the words around your cursor for exactly those reasons. Any page telling you it has found a keyboard that cannot see your text is describing something that would not function.
So the useful question is never "can it see my typing". It is "what does it do with what it sees, and what would it even be able to do".
Ruling out three things the word does not mean
"Private keyboard" gets used loosely enough to promise three things it does not deliver, so rule those out first.
It does not mean encrypted. Your keystrokes are not a message in transit, they are input to the app you are typing into, and encryption is not the relevant mechanism.
It does not mean anonymous. The app you type into knows perfectly well who you are. A keyboard cannot change that.
And it does not extend past the moment you press send. Once the words are in a message, a note or a form, they belong to that app and its rules. The keyboard's part ends when the text appears, exactly as if you had typed it yourself.
What is left is narrow and checkable: whether your typing is collected, whether your dictionary is synced, whether your voice is transmitted, and whether any of it needs a server. Four questions, and every one of them has an answer you can establish yourself.
The four things that actually decide it
Does it need the network at all? This is the strongest signal available to you, because it is binary and checkable. A keyboard that never contacts anything cannot send your typing anywhere, whatever its policy says. Some keyboards want a connection for genuinely useful features, translation, cloud clipboards, syncing your learned dictionary across devices. Those are conveniences with a cost, and the cost is that text leaves the device.
Is your learned dictionary stored locally or synced? Autocorrect improves by remembering your words. Where that memory lives matters: on the handset, or in an account that follows you to a new phone. Convenience and exposure are the same feature seen from two sides.
Is it excluded from backup? Android can back app data up to the cloud automatically. For most apps that is helpful, and for one that holds everything you have typed it is questionable. An app can opt out of it, and whether it does is a deliberate decision by whoever built it.
What happens in password fields? Android tells a keyboard when a field is a password. A careful keyboard changes its behaviour there, at minimum by not learning from what you type and not offering voice input.
Five minutes beats reading a privacy policy
Three checks, and none of them requires believing anything on a listing page.
Look at the permissions. In Android's app settings, see what the keyboard has been granted, and whether it requested internet access at all. A keyboard that was never given the network has no route to post your typing anywhere, whatever else turns out to be true about it.
Turn the network off and use it. Type for a day in airplane mode, dictate, switch languages, use the emoji picker. Whatever breaks was leaning on a server. Whatever carries on was never leaning on one.
Watch what happens on a new phone. If your learned words, your settings and your dictionary reappear without you doing anything, they were stored somewhere other than the old handset. If you start from scratch, they were not.
That last one is the clearest tell of all, and it cuts both ways: starting from scratch is mildly annoying and it is also the proof.
Keyboards worth a place on the shortlist
Open-source keyboards. Projects like AnySoftKeyboard and HeliBoard exist precisely because some people want to read the code and not simply trust a description. If that is your requirement, start there. They are free, and the trade-off is usually polish and the number of languages handled well.
FUTO Keyboard. Built around the same instinct, open source, paid once, with voice input available as a separate component you can attach.
The keyboard your phone shipped with. Mainstream keyboards are refined, fast and cover enormous numbers of languages. If you have read this far and nothing here worries you, there is no reason to change.
LocalType. A keyboard with dictation built in. The speech recognition runs on the handset, and no server is involved.
Whichever of those you shortlist, run the same three checks on it. A keyboard that is open source can still ask for the network, and a keyboard that came with your phone can still keep its dictionary on the device. The category tells you what to expect; the checks tell you what is true.
Our own answers to those four
Network. The app asks for internet access for exactly one purpose, fetching the speech model you choose, and it does not ask again after that. Typing has never needed a connection, and once the model is installed neither does dictation. You can verify that in airplane mode rather than taking our word for it.
Your dictionary. Words you add, surnames, jargon, product names, stay on the device. They improve typing suggestions and are also handed to the speech model as context so those words come out spelled correctly when you say them. They are not uploaded, because there is no service on the other end to upload them to.
Backup. The app's data is deliberately excluded from Android's cloud backup. The consequence is real: a new phone starts empty, and you install the app and fetch a model again. That is the cost of not putting your data somewhere it could be copied from.
Password fields. No microphone key appears there at all, so a password cannot be dictated by accident.
Beyond those four: no account exists, no sign-up, no profile, nothing linking the keyboard to a person. There is no advertising in the product, so nothing you type feeds a profile, and no behavioural tracking runs inside it. The speech model sits in storage only the app can read, and no archive of your recordings is kept, because audio becomes text and the audio is finished with.
What the clipboard sees
A keyboard usually offers a clipboard history. Convenient, and it also keeps a list of the last things you copied somewhere on the phone: bank details, one-time codes, addresses, passwords pasted from a manager.
Ask the same questions of it that you asked of your typing. Is that history on the device or synced to an account? Does it survive a reinstall? Can you clear it, and does clearing it actually clear it?
Two more belong to clipboards specifically. How many entries does it hold, and does anything expire on its own? And can an entry be pinned, since pinning is the setting that quietly converts a temporary list into a permanent one.
There is a check for this too. Copy a nonsense string you will recognise, force stop the keyboard, open it again and look at the history. Then uninstall the keyboard, reinstall it, and look one more time. Anything that came back was being kept somewhere other than the app you just deleted.
LocalType keeps its data on the handset and out of Android's backup, which answers those questions the same way it answers the others, and the general point stands whichever keyboard you end up with.