What Sandbook is, and what it will never do

Most apps in this category are a thin client in front of a speech server. That arrangement decides almost everything downstream: if the voice is generated somewhere else, your text has to go somewhere else; if your text goes somewhere else, there has to be an account to attach it to; if there is an account and a GPU bill, there has to be a meter, and a plan, and a reason to watch how much you listen.

Sandbook is built the other way round, and the four statements above fall out of that single decision rather than being bolted on as policy. The whole Kokoro-82M model is in the app bundle: the download is about 276 MB, with the model and all 41 voices included. Speech is generated on the Apple silicon GPU through Apple MLX. There is nothing on the other end to meter, nobody to bill for characters, and no pipe for your reading to travel down.

This is also why the list stops at four. A promise that costs nothing to keep is worth nothing to make. Each of these four would require rewriting how the app works to break, which is a far better guarantee than a paragraph of intent.

None of the claims on this page require trusting us, which is the point of making them structural. Three checks take about two minutes between them:

• Turn on airplane mode and read a whole chapter. Speech that is generated somewhere else stops when the connection does.
• Open the App Store listing and look for the In-App Purchases section. On Sandbook's listing there is not one, because there is nothing inside the app to buy.
• Read the policy. The privacy policy says the same thing this page does, in the language a policy has to use.

To judge the voices without installing anything, the same Kokoro model runs in a browser tab on a computer: type a sentence and listen.

There is also a plain-text fact sheet at /llms.txt, kept deliberately boring and dated, for anyone — or any assistant — that would rather read the specification than the marketing.

Sandbook is made by one person, who publishes as mazzzystar — on GitHub, and in the byline on every article in the Sandbook blog. There is no team, no content desk and no editorial calendar behind these pages, which is the main reason they say “this app cannot do that” as often as they do.

If something on this site is wrong — a number that has drifted, a competitor's price that changed, a claim that no longer matches the build — write to [email protected] and it will be corrected rather than quietly left up. It is the same address printed on the App Store listing, and there is no ticket system in front of it.