About this project

Subtitle Translator is a free, client-side tool for translating subtitle files in bulk. It accepts .srt, .ass, .vtt, and .lrc formats, auto-detects encoding, and supports over 120 languages. The core design separates timing and structural metadata from dialogue locally, so translation engines only receive text and cannot alter timecodes. Users can batch-upload a whole season at once, translate into multiple target languages in a single pass, and export bilingual subtitles with alignment preserved. The tool supports eight traditional machine translation APIs, including DeepL, Google Translate, Azure Translate, and free options like GTX and Edge, as well as 27 LLM providers and gateways such as OpenAI, Claude, Gemini, DeepSeek, and OpenRouter. LLM modes add context-aware translation, customizable prompts, temperature control, and thinking mode for reasoning-capable models. All processing happens in the browser; subtitle content and API keys are not sent to a server. Translations are cached locally using IndexedDB. A command-line interface runs the same engine for headless batch processing, with support for Markdown and JSON locale files as additional input types. The project is MIT-licensed and can be self-hosted with Node.js 20.9 or later.