Read articles, PDFs, and documents aloud without ever sending your data to the cloud. Fully offline synthesis powered by local ONNX transformers, with optional Bring-Your-Own-Key cloud speech.
"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.
Plug in your personal OpenRouter API key. Encrypted at rest via Web Crypto AES-GCM with zero platform fees, no credit lock-in, and direct provider billing.
Seamlessly switch to high-performance remote models like Gemini Flash, 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.
Listen locally for free, connect your personal OpenRouter key, or top up your USD wallet on demand.
Synthesize speech locally on your device with no limits and absolute privacy.
Connect your personal OpenRouter API key. Pay your AI model provider directly with zero Castor credit markups.
No API keys required. Load your prepaid USD wallet to invoke premium remote models and voices on demand.