Read articles, PDFs, and documents aloud without ever sending your data to the cloud. Fully offline synthesis powered by local ONNX transformers.
"Human speech is a delicate mechanism of waves. In the local sandbox of the modern browser, Castor processes and synthesizes language directly, guaranteeing absolute privacy."
Everything you need for an immersive, robust document listening experience, packaged in an offline-first PWA.
Your private documents remain strictly private. Speech synthesis and parsing run inside secure browser sandboxes, preventing external server leaks.
Seamlessly switch to high-performance remote models like Gemini-Lite, Voxtral, or Orpheus for premium cloud voice capabilities under user consent.
Keep your reading list stored directly on your disk via Origin Private File System (OPFS) binaries and IndexedDB relational catalogs. Listen anywhere, anytime.
No playback cutting off. Using custom silent loop mechanisms, Castor continues running seamlessly in the background and respects native lock screen control keys.
Save and restore your personal reading lists and scripts effortlessly across multiple devices with secure, encrypted cloud backup.
A gorgeous layout designed for mobile, tablet, and desktop viewports alike. Supports smooth animations, interactive sliders, and strict light/dark custom color themes.
Castor relies on the power of modern client-side APIs to render, manage, and read text without intermediate servers.
Paste raw text or upload a PDF/DOCX file. Castor's native Web Worker parsed extraction splits text into clean sentence arrays instantly.
Scripts are saved in IndexedDB, and parsed audio bundles are saved into Origin Private File System (OPFS) as high-quality WAV buffers on your device's local drive.
Castor reads sentences aloud using in-browser Kokoro pipeline transformers, or queries OpenRouter API when choosing premium remote models online.
Listen locally for free, or top up your USD wallet for premium remote model support.
Synthesize speech locally on your device with no limits and absolute privacy.
Load your wallet to invoke premium remote models and voices on demand.