User Guide

Translate entire books with AI, right on your own computer.

What is Libyx?

Libyx is a desktop application for macOS and Windows that translates books using AI — EPUBs, and PDFs it rebuilds into EPUBs first. You download the app, connect an API key from an AI provider of your choice, and can then translate whole books directly on your computer.

Core principles:

• No Libyx server, no subscription. You pay the provider (Anthropic, Google, OpenAI, and others) directly — Libyx takes no cut.
• Your book never leaves your computer except to the AI provider you chose yourself.
• No Libyx accounts, no data collection.
• A typical novel costs from under $1 to about $3 depending on the model — and Batch mode halves what you pay.

Installation

Libyx is available for both macOS and Windows. Download the right version from libyx.app — the site has separate downloads for each platform.

macOS

Libyx runs on both Apple Silicon (M-series) and Intel-based Macs. These are two separate downloads — pick the one that matches your computer. Not sure which you have? Click the Apple menu → About This Mac; if it says "Apple M1/M2/M3…" it's Apple Silicon, if it says "Intel" it's Intel.

1. Download the DMG file for your architecture from libyx.app.
2. Open the DMG and drag Libyx into your Applications folder.
3. Launch the app.

Windows

1. Download the Windows installer (Libyx_…_x64-setup.exe) from libyx.app.
2. Run the installer and follow the steps.
3. Launch Libyx from the Start menu.

About the SmartScreen warning: When you first run the installer, Windows will show a SmartScreen warning ("Windows protected your PC"). To proceed, click More info and then Run anyway.

This warning appears because the app is not signed with an Authenticode certificate, and it will keep appearing — the app is not going to be signed. Authenticode signing is a recurring annual cost, and Libyx is developed and maintained by a single person, so this expense isn't justified for the project. The warning is expected and does not indicate anything wrong with the download. If you'd rather be certain, you can verify the installer against the signature published on libyx.app.

Step 1 — Add an API key

Libyx needs an API key from at least one AI provider in order to translate. The key is what gives the app access to the provider's models, and the provider is who you pay — not Libyx.

Open Settings (the gear icon in the top right) and add your key. There are six providers to choose from, plus any OpenAI-compatible endpoint of your own.

Google — easiest to start with

• Free to start. No credit card required.
• Google offers a free tier for its Gemini models with daily usage limits.
• Please note: daily limits apply, and not every Gemini model is included. Libyx checks what your key's plan allows when you add it and greys out what the free tier can't do — so you see what works before you spend anything.

How to get a key:

1. Go to aistudio.google.com/apikey
2. Sign in with a Google account (Gmail works)
3. Click Get API key → Create API key
4. Copy the key (starts with AIza…) and paste it into Libyx Settings

Note: Batch mode (50% discount) is not included in the free tier — for that you need to add at least $10 in credits. On the free tier, Google may use your translations to improve its products. The paid tier protects your data.

Anthropic — makes Claude · Libyx’s default

• New accounts get a small starting credit; most people will need to top up for longer books.

How to get a key:

1. Go to console.anthropic.com
2. Create an account and verify your phone number via SMS
3. Go to Settings → API Keys → Create Key
4. Copy the key (starts with sk-ant-…) and paste it into Libyx Settings

A typical novel on a mid-tier Claude model in Batch mode costs $1–2.

OpenAI — GPT-5 family · card required

• Credit card required, minimum $5 prepaid.

How to get a key:

1. Go to platform.openai.com
2. Go to Settings → Billing and add a payment method
3. Go to API Keys → Create new secret key
4. Copy the key (starts with sk-…) and paste it into Libyx Settings

Mistral — EU-hosted, low prices

• Credit card required.
• EU-hosted (your book data stays in the EU); Mistral Large 3 has a 256K context and among the lowest per-token prices. Whether it suits your target language is worth checking with a Preview chapter.

How to get a key:

1. Go to console.mistral.ai
2. Add a payment method
3. Go to API Keys → Create new key
4. Copy the key and paste it into Libyx Settings

DeepSeek — low prices, China-hosted

• Credit card required; you top up a small balance up front.
• Two models, both marked beta in the app: V4 Flash, its cheap workhorse, and V4 Pro, a frontier-class model for a fraction of what frontier models normally cost. Both have a 1M-token context.
• Please note: DeepSeek runs on servers in China, and the text you translate is sent there. If that matters for your book, pick another provider.
• No batch mode. DeepSeek doesn't run a batch queue, so these models are realtime only — there is no 50% batch discount to be had. That is worth weighing before calling it the cheap option: a provider that does offer batch can end up cheaper per book at a higher list price. The Polish pass does work.
• DeepSeek bills by time of day: a run costs half as much outside its two daily peak windows. The app shows those hours converted to your own time zone.
• Translation runs with reasoning set to High by default. Under Advanced options you can lower it — reasoning is billed as output you never see — and let DeepSeek translate up to 8 chapters at once, which is much faster.

How to get a key:

1. Go to platform.deepseek.com
2. Create an account and top up a small balance
3. Go to API keys → Create new API key
4. Copy the key and paste it into Libyx Settings

OpenRouter — one key, many models

• Acts as an intermediary layer: you buy credits and can use models from Anthropic, OpenAI, Google, DeepSeek, Meta, and others with a single key.
• $1 in free credits on sign-up.
• Note: Batch mode and the Polish pass are not supported via OpenRouter.
• Note: Libyx can't estimate costs for OpenRouter models — the app shows “Cost varies by model” instead of a figure. The translation still costs money: it is deducted from your OpenRouter credits, so track your usage on openrouter.ai.

How to get a key:

1. Go to openrouter.ai
2. Sign up and create a key under Settings → Keys
3. Copy the key (starts with sk-or-…) and paste it into Libyx Settings

How your keys are stored

Your keys are saved in the file api_keys.json in the Libyx data folder (see Where are files stored? below), with read access restricted to your user account. They are never sent to any Libyx server — only directly to the provider they belong to.

Step 2 — Translate a book

The Translate view walks you through five steps.

1. Book

Drag an EPUB file onto the app window, or click the drop zone to browse for a file. Once the book is loaded, Libyx shows an estimated time and cost for the translation. A PDF can be dropped here too — it is converted into an EPUB first, and Translating a PDF below describes what that involves.

2. Languages

Choose the source and target languages. The default is English → Swedish. Click Change to open the language pickers and ← Done to close them. Over 40 languages are supported.

3. Glossary — optional

A glossary is a list of the book's names and special terms, each with a chosen translation. Libyx can build one before translating: it reads a sample of the book for names, scans the whole text for recurring terms, and sends the list with every chapter — so the same invented word is more likely to come out the same way in chapter 2 and in chapter 30.

• It is not free, and it is not recommended for most books — an ordinary novel rarely repays it. Switch it on for science fiction, fantasy, or anything built on invented words. The app explains the trade-off, and the cost, right where you turn it on.
• Libyx pauses so you can review and edit the list before the translation starts — or you can skip the automatic build and write the list yourself.

Voice & style analysis — a separate switch, and it runs with or without the glossary:

• A model reads representative chapters and writes a short profile of how the book is told — tone, pacing, rhythm — which the translation then follows.
• Worth it for novels and strongly-voiced writing; rarely needed for plain non-fiction.
• The cost is small and does not grow with the book's length — it reads a fixed-size sample.

4. Translation model

Choose which AI model will translate the book. Models are grouped by provider (Anthropic, OpenAI, Google, Mistral, DeepSeek, OpenRouter).

Sensible starting points — translation quality varies a lot by target language, and no single model wins everywhere. The one reliable test is your own: run a Preview chapter and judge the result before committing to a long run.

• Literary fiction — try a Claude model first; the family is often favoured for literary tone and dialogue.
• Broad language coverage, including lower-resource languages — Gemini's frontier models are a common pick.
• Keeping your book data in the EU — Mistral is EU-hosted.
• On a budget — Mistral Small carries the lowest list price and takes the 50% batch discount on top. DeepSeek's V4 Flash is the next cheapest, and cheaper still outside its peak hours, but it is realtime only and processes your text in China.

The app's model cards carry current star ratings, prices, and a cost estimate for your actual book, grouped by provider or by quality tier. That list is kept up to date with each release — trust it over anything written here.

5. Speed — Batch or Realtime

Batch (recommended, −50% in price):

• Sends the book to the provider's queue and costs half as much as Realtime.
• The provider guarantees delivery within 24 hours, but in practice the job is often finished considerably faster.
• Once you see "Batch submitted…" in the status bar, the job is in the provider's hands and Libyx will collect the result and assemble the EPUB the next time you open it.
• Important: Wait until you see "Batch submitted…" before closing the app. If Glossary or Voice analysis is enabled, a local preparation pass runs first (anywhere from 30 seconds to a few minutes) before the job is sent off. If you shut down during that step, the job is cancelled.
• A note on closing the app: In principle you can close Libyx, and even shut down your computer, after "Batch submitted…" appears, and Libyx will retrieve the finished book when you reopen it. However, this close-and-resume flow has not been thoroughly tested. If it's important to you that the book comes through reliably, the safest approach is to leave Libyx running until the job completes.
• Not every provider offers batch — Libyx greys out the option where it isn't available.

Realtime:

• Results appear while the job runs.
• You can cancel at any time.
• Full price.

Polish — after translating

Polish is a separate, optional second pass that re-reads a finished translation and rewrites it to sound more natural in the target language — fixing stiffness, improving rhythm, and matching the author's voice. It roughly doubles the cost and time, and it's worth it for novels and literary texts; rarely necessary for simple non-fiction.

You run it from your Library once a translation is done — see Polishing a finished book below.

Preview a chapter

Before starting a full translation, you can click Preview chapter to:

• Translate one representative chapter and see the result side by side with the original.
• Get a cost estimate for the whole book based on that chapter.
• Try a different model without paying for the entire book.

In preview mode you can choose the model and enable glossary, voice analysis, and polish independently of the main settings.

Start the translation

Click Start translation →. During translation you'll see:

• A chapter grid showing the status of each chapter (pending / in progress / done / failed / skipped).
• A progress bar with the current phase and chapter count.
• The book cover, if the EPUB contains one.
• An estimated cost that updates in real time.

You can cancel with Cancel at any time during a Realtime job.

The result

When the translation is complete, Libyx shows the path to the finished EPUB file, the total cost, and a Show in Finder (macOS) / Show in Explorer (Windows) button that takes you straight to the file. The file is saved automatically in the Libyx data folder.

Polishing a finished book — post-processing

If you already have a translated book, you can polish it separately from your Library. There is no separate Polish tab — polish is started from the book itself.

1. Open the Library tab, find the finished book, and click Polish this book.
2. Choose intensity: Light (minor adjustments), Standard (balanced), or Strong (deeper rewrite).
3. Choose the polish model and provider.
4. Add translation notes (optional): after polishing, an AI reviewer re-reads the result, adds an “About this translation” page to the book, and shows a quality report comparing the translation before and after. Still experimental — the reviewer's judgments can be uneven.
5. Choose Speed (Batch or Realtime) and Temperature.
6. Click Start polish →.

Temperature controls how freely the model rephrases sentences:

• 0.0–0.5 — conservative; stays close to the original translation.
• 1.0 — balanced; natural flow, faithful to the content.
• 1.5–2.0 — creative; more rephrasing, but a higher risk of drift.

Translating a PDF

A PDF is dropped on the app the same way an EPUB is. It cannot be translated as it stands — a PDF is a description of printed pages, not a book — so Libyx reads the text out of it and rebuilds it as an EPUB first. That reading happens entirely on your computer.

Libyx asks what kind of PDF it is, because the answer changes how the pages are read:

• A book — one continuous text. Libyx finds the chapters afterwards.
• A magazine or newspaper — each article becomes a chapter. Adverts, contents lists and chart labels are left out.
• A single article or paper — one piece with an abstract, sections and notes. Its top-level sections become chapters; numbered subsections stay inside them.

Pictures come across with the text, though not all of them: one that fills a whole page, or that the typesetter cut into tiles, is left behind. The page layout does not come across at all — the result is a reflowable book, which is what makes it readable on a phone or an e-reader.

The one step that costs money is optional and is offered before the import runs: Mend words broken across line ends. Print breaks words at the right-hand margin, and only some of those hyphens belong to the word. A small model decides which are which — the default is Gemini 3.1 Flash Lite, right about 97% of the time and the cheapest of the options. Switch it off and the hyphens are left as the page had them.

A pure scan cannot be translated. If the pages are photographs of text with no text layer underneath, there is nothing to read and Libyx says so rather than guessing. Text recognition is not part of Libyx today.

Proof & Fix — after the import, the button next to the verdict opens the imported book so you can read it and correct it before paying to translate it. It has three modes: Proofread (the book's own text, nothing beside it), Structure (its chapters, and what can be done to them — rename, split, join), and Review findings (what the import did, and the paragraphs worth a second look). The view also keeps a receipt of the import: how many running heads were taken out, how many broken words were rejoined, how many page numbers were dropped. Everything you change is written straight into the book.

Collect — turning articles into a book

The Collect tab builds a book out of things that were never one. Articles gather in a pile, wait as long as you like, and are bound into a single EPUB when the pile is worth reading — which you then translate like any other book.

There are three ways in:

• Paste a link into the field at the top and press Add. Libyx fetches the page from your machine, strips the navigation and the advertising, and files the article into the pile.
• Paste text… opens a dialog for pasting an article you already have on the clipboard. The dialog also takes an address of its own, and shows you what came back before anything is added. This is where the Fetch pictures switch lives.
• Add EPUBs…, or drop EPUB files anywhere on the view.

Rows can be reordered by dragging, renamed, opened in the reading view and corrected, or removed. The panel beside the pile shows the book as it stands — its chapters, its word count, and an estimate of what translating it would cost. Click the title on the cover to name the book, and drop a picture on the cover to make it the cover.

Bind into a book turns the pile into one EPUB in your Library. The pile is not emptied by binding: an article stays where it is, marked as having been in a book, and can go into another one later.

What leaves your machine when an article is fetched is described in the privacy policy — briefly: one request to the address you gave, no cookies, no account, and no record of it anywhere but your own computer.

Advanced settings

Accessed via the Advanced button next to the Start button.

Models and pricing

Model prices change too often for a page like this to stay honest, so they live in the app instead: the $ Prices button above the model list shows every model's current price, and each model card shows an estimated cost for your actual book before anything starts. All prices and estimates are in USD.

Two things hold generally: output costs more than input (a translated chapter produces several times more text out than in), and Batch halves what you pay on every model that supports it. A typical novel runs from under $1 to about $3 depending on the model.

Where are files stored?

Libyx stores all of its files in a data folder on your computer:

• macOS: ~/Library/Application Support/Libyx/
• Windows: %LOCALAPPDATA%\Libyx\ — typically C:\Users\<your name>\AppData\Local\Libyx\

The folder contains:

Privacy and data protection

• No Libyx server. There is no Libyx backend. The app never communicates with the Libyx project.
• Your book text is sent directly from your computer to the AI provider you chose. The Libyx project never sees your text, your translations, or your API calls.
• No API keys are passed to anyone other than the provider they belong to.
• No telemetry. No crash reports and no usage statistics are sent.
• The bug report in Settings automatically redacts file paths and book titles, and is not sent anywhere automatically — you copy and share it manually.
• Read each provider's own privacy policy to understand what they do with your text once they receive it.

Troubleshooting

SmartScreen warning on launch (Windows)

Click More info → Run anyway. The warning appears because the app is not signed with an Authenticode certificate, and it is expected — see the Installation section above for why the app is not signed.

"No API key set" — the Start button is greyed out

Open Settings (the gear icon) and add a key for the provider you've chosen.

The batch job is taking a long time

Batch jobs are handled by the provider's queue. The provider guarantees delivery within 24 hours, but the job is often finished considerably sooner. In principle you can close the app and come back later — but that flow isn't fully verified yet, so if reliability matters, leave Libyx open until the EPUB is assembled (see the note under Speed above).

Cancelling a running batch job

Click Cancel in the progress view. Note that you pay for the work the provider has already done — cancelling stops further charges but does not refund the portion already completed.

Creating a bug report

Settings → Generate report creates a diagnostic report with logs, version, and settings (without API keys or personal file paths). Send it to [email protected].

Contact and support

Email: [email protected]

Support the project: ko-fi.com/blackislandcrew