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 EPUB books using AI. 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 300-page novel costs €0.50–€3 depending on the model.

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 five providers to choose from.

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: Libyx has not tested the Google free tier, so we can't confirm which Gemini models it covers, what the current daily limits are, or whether it's sufficient to translate a full book. Treat it as a starting point to experiment with, and check Google's own terms and current limits before relying on it.

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 — best for literary quality

• 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 with Claude Sonnet 4.6 in Batch mode costs €1–2.

OpenAI — reliable option

• 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 — European, good value

• Credit card required.
• Mistral Large 3 is excellent for Nordic and Romance languages.

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

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's cost estimate does not apply to OpenRouter models — the app shows €0 for them. This does not mean the translation is free; the cost is deducted from your OpenRouter credits. Track your actual 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 is divided into six numbered 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.

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 (auto-glossary)

Enabled by default.

Before Libyx starts translating, it reads through the entire book and builds a list of character names, places, and recurring terms. This list — the glossary — is then used throughout the translation to ensure the same name or term is translated consistently in every chapter.

• Without a glossary, the same character could end up with inconsistent name spellings from one chapter to the next.
• You can choose a separate, cheaper model for glossary extraction. This is recommended — the task is mechanical rather than creative.

Voice & style analysis (requires Glossary to be enabled):

• A separate model reads representative chapters to capture the author's tone, pacing, and rhythm.
• Produces more faithful, natural-sounding translations.
• Recommended for fiction; rarely necessary for simple non-fiction.
• The default model is Claude Opus 4.7, but you can choose another.

4. Translation model

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

Recommended for most users:

• Claude Sonnet 4.6 (Anthropic) — the best balance of quality and cost, and the default choice in Libyx. Strong at preserving voice and dialogue register.
• Gemini 3.1 Pro (Google) — the strongest multilingual performance in the Libyx selection. A good choice if you have a Google key.
• GPT-5.4 (OpenAI) — OpenAI's production model. Solid general-purpose translation.
• DeepSeek V4 Flash (via OpenRouter) — the cheapest option; runs in realtime mode.

Model choice by language group:

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.
• Available via Anthropic, OpenAI, and Google (not Google's free tier, not OpenRouter).

Realtime:

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

6. Polish

Disabled by default.

Polish is an extra pass where a model reads through each chapter and rewrites it to sound more natural in the target language — fixing stiffness, improving rhythm, and matching the author's voice.

• In the worst case, Polish roughly doubles time and cost. In practice it's usually less: with Reviewer enabled (see the Polish tab below), each chapter is assessed first, and those that are already well written are skipped — so you only pay for polish where it's needed.
• Worth it for novels and literary texts; rarely necessary for simple non-fiction.
• Requires Glossary to be enabled.
• Advanced settings: choose a separate polish model and intensity (Light / Standard / Strong).

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.

The Polish tab — post-processing

If you already have a translated book, you can polish it separately via the Polish tab.

1. Select a book from the list.
2. Choose intensity: Light (minor adjustments), Standard (balanced), or Strong (deeper rewrite).
3. Choose the polish model and provider.
4. Reviewer: An AI reads each chapter before it is polished and judges whether the text actually needs improvement. Chapters that are already well written are skipped — saving both time and money. Enabled by default; Claude Haiku 4.5 is plenty, since the task is a simple yes/no decision.
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 (default) — balanced; natural flow, faithful to the content.
• 1.5–2.0 — creative; more rephrasing, but a higher risk of drift.

Advanced settings

Accessed via the Advanced button next to the Start button.

Models and pricing

Prices are in USD per million tokens. Output dominates the cost — a chapter typically produces 4–6 times more output tokens than input tokens. In-app estimates are shown in EUR (1 USD ≈ 0.92 EUR).

Batch mode halves the cost for every model that supports it (Anthropic, OpenAI, and Google's paid tier).

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. You can leave the app and come back later — Libyx retrieves the result automatically the next time you open it.

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 blackislandcrew+libyx@gmail.com.

Contact and support

Email: blackislandcrew+libyx@gmail.com

Support the project: ko-fi.com/blackislandcrew