Shinkansen - Blazing fast web & YouTube translator

Recently added: • New floating button: tap to translate the page, long-press to switch translation engines or open the menu • New Send to Instapaper: save the entire translated article to Instapaper in one click for later re-reading • iOS / iPadOS version coming soon to the App Store — stay tuned

Highlights: • Privacy-first — connects directly to Google, no third-party servers in between • Open source — the code is public on GitHub, so anyone can audit its security • Multilingual translation + multilingual UI — Traditional Chinese / Simplified Chinese / English / Japanese / Korean / Spanish / French / German

Web page translation • Instant streaming: the page starts changing into your language within 1 second of pressing translate — no waiting for the full API batch to return (Gemini only) • Translated paragraphs are cached automatically, so re-translating costs nothing • Two display modes: "Monolingual" replaces text in place; "Bilingual" shows the original and translation side by side • Edit translations: after translation completes, edit the translated text directly on the page to polish rough spots before exporting to PDF • Multilingual translation + multilingual UI — Traditional Chinese / Simplified Chinese / English / Japanese / Korean / Spanish / French / German • Translate-the-opening option: translate only the first N paragraphs as a preview, saving a large amount of tokens

PDF translation (beta) • Analyzes the layout locally, sends the text for translation, and presents the result in a side-by-side two-page comparison view • The entire document is processed inside your browser — nothing is ever uploaded to any server • Edit PDF translations: edit the translated text paragraph by paragraph inside the reader, then save to regenerate the two-page preview • Document glossary: before translating, ask the AI to extract a glossary of names and proper nouns from the document; confirm or edit it, then translate — keeping terminology consistent throughout the entire document

YouTube caption translation • Translates YouTube captions in real time, with caption styling that matches native YouTube • AI smart sentence segmentation: auto-generated (ASR) captions are re-segmented by meaning, turning fragmented short lines into readable full sentences • Bilingual captions: original + translation shown on two lines at once — great for listening practice

Three translation shortcuts / three engines • Alt+A / Alt+S / Alt+D each bind to a preset translation engine • Gemini AI (best quality, requires an API key) • Google Translate (free machine translation, no API key needed, faster) • Custom AI model (OpenAI-compatible — connect to hundreds of models via OpenRouter / Claude / DeepSeek / Groq / local Ollama, and more)

Translation quality control • Fixed glossary: force specific terms to always be translated the way you specify (global + per-domain layers) • Customizable banned-word list: explicitly tell the LLM which words it must never use • Document-wide terminology consistency: names and proper nouns stay consistent throughout long articles • Translate-the-opening option: translate the first few paragraphs as a preview before deciding whether to read on, saving a large amount of tokens

Auto-translate and cross-page continuation • Auto-translate specified sites: add a domain and pages are translated automatically on entry • Cross-tab continuation: open a link from a translated page in a new tab, and the new tab is translated automatically with the same preset

Usage tracking and savings reports • Records token counts, cost, and cache hit rate for every translation, with charts and CSV export • Two-layer caching (local cache + Gemini implicit context cache), with cache hit rate and actual savings shown right after each translation