Why does ClickBook need an AI model before I can read?

ClickBook explains words using an AI model that runs entirely on your device, so nothing you read is sent anywhere. That model has to be present before the reader can work. On iPhone and iPad it ships inside the app, so there is nothing to download. On Android it is downloaded once, roughly 1.73 GB, the first time you open the app.

What files can I open in ClickBook?

EPUB files, and PDFs that contain real text. Scanned PDFs, where each page is a photograph of paper, cannot be read or tapped because there is no text layer to extract.

ClickBook support

Support & FAQ

Q: What does ClickBook Pro unlock?

The Translation and Context tabs in the word popup, Think deeper for a more considered explanation, the mother-tongue language picker, and control over the order of the AI prompts. Meaning and Example are free. Pro is a single one-time purchase, not a subscription.

Q: How do I restore my ClickBook Pro purchase?

Open ClickBook, go to Settings then Purchases then Restore Purchases, and make sure you are signed in to the same store account you bought with. The restore option is also available on the upgrade screen.

Questions, problems or feedback about ClickBook on iPhone, iPad or Android? Email [email protected] and you will get a reply. Most common questions are answered below.

Contact

Email: [email protected]

To help diagnose a problem quickly, please include your device model, the operating system version, and what you were doing when the problem happened. Never send us book files you do not have the right to share.

Setup and the on-device AI

Why does ClickBook need an AI model?

ClickBook explains words using a model that runs entirely on your device, so nothing you read is sent anywhere. That model has to be present before the reader can work. It is roughly 1.73 GB — large, because it is a real language model rather than a dictionary lookup.

Do I have to download it?

On iPhone and iPad, no. The model ships inside the app, so it is already there when you install and nothing is downloaded at first run. This makes the app itself large in the App Store, but it means the reader works immediately and offline from the very first launch.

On Android, yes — once. The model is downloaded the first time you open the app. Use Wi-Fi if you can. It is a one-time download, not a subscription, and after it finishes word lookups work with no internet connection at all.

The Android download failed or stopped partway.

Reopen ClickBook and the download resumes from where it stopped. It pauses automatically when you leave the app and continues when you come back. If it will not start, check that you have at least about 2 GB of free storage — ClickBook asks for the model size plus some headroom before it begins.

ClickBook asked me to download the model again.

On Android the model file is large and can always be fetched again, so it is stored in a location your operating system is allowed to reclaim when the device runs very low on storage. It is also kept out of your device and cloud backups so those stay small. If the system reclaims it, ClickBook returns to the setup screen and offers to download it again. Freeing up storage makes this much less likely.

Which device do I need?

On iPhone and iPad, ClickBook requires iOS or iPadOS 15.1 or later on a device with an A12 Bionic chip or newer. Running a language model locally is demanding, and older hardware cannot do it reliably. On Android, a reasonably recent device with enough free storage is needed for the same reason.

Books and importing

What files can I open?

EPUB files, and PDFs that contain real text. ClickBook converts an imported PDF into a reader-friendly format so you can change the font, size and page colour, and so word tapping works.

My PDF will not open.

Scanned PDFs — where each page is a photograph of paper rather than text — cannot be read or tapped, because there is no text to extract. ClickBook tells you when it detects one. Very complex layouts may also convert imperfectly.

Where do my books come from?

From your own device. On iPhone and iPad you pick them through the Files app, including iCloud Drive; on Android through the system file picker. ClickBook copies the file into its own library so your reading position and settings stay with it. Public-domain sample books are included so you can try the app immediately.

Reading and word lookups

How do I look a word up?

Tap it. ClickBook highlights the word, reads the sentence around it for context, and writes a meaning, an example, a translation and a contextual explanation. The first answer appears quickly; the remaining tabs fill in shortly afterwards.

Why do the other tabs take a moment?

Each tab is generated separately by the on-device model. They are spaced slightly apart on purpose, so the phone is not running the model continuously and does not get warm. If you switch to a tab that has not finished yet, it jumps the queue and starts immediately.

Can I change how the reader looks?

Yes — font family, text size, line height, page colour (including sepia and dark), and paged or scrolling reading mode.

ClickBook Pro

What does Pro unlock?

The Translation and Context tabs in the word popup, “Think deeper” for a more considered explanation, the mother-tongue language picker, and control over the order of the AI prompts. Meaning and Example are free. Pro is a single one-time purchase, not a subscription.

How do I restore my purchase?

Open ClickBook, go to Settings → Purchases → Restore Purchases, and make sure you are signed in to the same store account you bought with. The restore option is also available on the upgrade screen. ClickBook never restores purchases silently in the background.

I bought Pro on Android — why is it not unlocked on my iPhone?

ClickBook has no accounts, so a purchase belongs to the store account you made it with. The App Store and Google Play run separate billing systems with no way to link them without an account, so a purchase on one does not carry over to the other. This is a deliberate trade-off for not asking you to sign up for anything.

I want a refund.

Refunds are handled by the store you bought from, not by ClickBook. Use Apple's Report a Problem page for App Store purchases, or the Google Play order history for Play purchases. If something in the app is broken, email us first — we would rather fix it.

Privacy

ClickBook has no accounts, no advertising, and no analytics. The text of your books and the words you tap are processed on your device and are never sent to us. Full details are in the Privacy Policy.

Open source

Word explanations are generated by Gemma 4 E2B XS, running through llama.cpp. ClickBook also builds on React Native, Expo, epub.js and other open source libraries. The full list, with licences, is in the app under Settings → Open Source Licenses.