Nothing here is waiting to be unlocked

“Free” in this category is normally a shape rather than a fact, and it is worth naming the shapes before claiming the word. A text-to-speech app usually becomes paid in one of four ways:

• A character cap. Five hundred characters per note, or a few thousand per day — enough to test, never enough to read a chapter.
• A listening quota. So many minutes or hours a month, refilled on a billing date, gone the night before a deadline.
• Locked voices. The free tier gets two or three flat ones; the voices you would actually listen to for an hour are the premium pack.
• A trial that converts. Everything works beautifully for seven days, and then the app you built a habit around asks for a card.

Sandbook has none of the four, and not as a promotional position. There is no in-app purchase in the app at all, so there is no tier for anything to be held back from. Nothing counts your characters, nothing counts your minutes, nothing counts your documents, and all 41 voices are bundled in the download with nothing marked premium. You can also try the voices online, free, on a computer, before installing.

There is also no account. No email, no Apple sign-in, no sign-up screen anywhere in the app — which means nothing to cancel, nothing to restore on a new phone, and no password to forget.

The reason is not generosity, and you should not have to take it on trust. It is a consequence of where the audio is made.

A cloud reader meters you because every minute of speech it produces costs it money — GPU time on someone's server, billed per character. Charging you per character is how that app stays solvent, and no amount of goodwill changes the arithmetic.

Sandbook generates speech on your own device. Kokoro-82M runs on the iPhone or iPad GPU through Apple MLX, so a book you listen to costs the people who made the app precisely nothing. There is no per-character cost to pass on, and therefore no reason to count characters in the first place.

The second question is fair too: if not money, then data? No. Sandbook shows no ads and does not track you, and everything stays on your device (the privacy policy has the details). Your books are copied into the app's own storage and never uploaded; your position, each book's voice and speed, and your starred voices live on the phone.

So there is no ad tier, no reading history to resell and no account graph to be worth something later. Free here is an absence of billing code, not the first step of a funnel.

A claim this broad is only believable if it is specific. Everything in this list is in the free app, which is the only app there is:

• 41 voices in six languages: 28 English voices (20 American, 8 British; the default is Heart), plus Spanish, French, Italian, Brazilian Portuguese and Hindi. Audition any of them before you commit to a book.
• EPUB, PDF, TXT, RTF, Markdown and HTML import, plus typed or pasted text, your clipboard and web pages, with nothing counting characters, documents or minutes.
• Scan printed pages with the camera, or pick a photo, and hear them read aloud. The text is recognized on your iPhone.
• Word-by-word highlighting inside a tinted current paragraph, tap any paragraph to read from there, and every book opens where you stopped.
• PDF line-wrap repair — visual line breaks rejoined and hyphenated words stitched back together, so a paper reads as prose rather than as a list of lines.
• Reading options: light, sepia and dark themes; System, Serif, Rounded, Mono and Legible fonts; text size and line spacing on top of your system text size.
• Speed from 0.5× to 2.5×, applied inside the model rather than by resampling the finished audio, and remembered per book along with its voice.
• Listen with the screen locked by preparing a chapter's audio ahead of time; real-time reading pauses when the screen locks.
• M4A export from the Reader tab, and Continue Reading through Siri and the Shortcuts app.
• Everything above with no connection, including on the first launch, straight out of the box.

The honest half. None of the following is a paywall — there is no tier where these appear. They are simply not in the app, and if one of them is the thing you need, you should install something else.

• Six voice languages, not dozens: US and UK English, Spanish, French, Italian, Brazilian Portuguese and Hindi. French has one voice.
• iPhone and iPad only, on iOS 18.2, with an iPhone 12 or later or an iPad with an A14 or M1 chip or later. There is no Android or web version.
• Real-time reading pauses when the screen locks. The model holds real GPU memory while it works. You can prepare a chapter's audio ahead of time and listen to that chapter locked, but a whole book will not play on in your pocket.
• No text recognition for image-only PDF files. Camera scans and photos are read; a scanned PDF file is not.
• No DOCX or MOBI, no iCloud sync between devices, no voice cloning and no sleep timer.
• No whole-book export. Text in the Reader tab exports as M4A; you cannot turn an imported book into an audiobook file.

That list is the price. If it is acceptable, the rest of the app is genuinely, permanently free — and you can verify every line of this page in about two minutes inside the app itself.