Shinkansen Web Translator

Shinkansen is a fast, smooth, privacy-first Safari translation extension for web pages and YouTube subtitles, built for iPhone and iPad. Three things make it different:

• Watch the page start turning into your target language within one second of pressing translate (Instant Translation, Gemini engine)
• Text is replaced in place — fonts, sizes, colors, and layout are preserved; links, bold, and italics survive untouched
• You bring your own API key; every setting lives on your own device; your reading never touches a third-party server

[Built for iPhone & iPad]

• Three- or four-finger tap any web page to toggle translation (tap again to restore) — no keyboard needed
• Hardware keyboard shortcuts when an external keyboard is attached
• Hover translation with a trackpad or mouse: hold a modifier key and rest the cursor on a paragraph to translate just that one
• First-launch onboarding walks you through your Gemini API key and a default translation method

[Languages]

Translate into 8 target languages. The extension UI is available in the same 8 languages — pick independently or follow your system language.

[Features]

• Three engines: Gemini (best quality, API key), Google Translate (free, no key), any OpenAI-compatible model
• Single-language overlay / bilingual side-by-side modes — one-click toggle, with 4 visual treatments for the bilingual layout
• Free Chinese variant conversion: built-in dictionaries, no API key, works offline; auto-convert on by default
• YouTube subtitle translation: real-time replacement styled like native captions; bilingual option; live stream links supported
• YouTube AI smart segmentation: auto-generated captions are re-segmented by AI for natural full sentences
• Adjustable YouTube subtitle size, readable even in full screen
• Custom translation shortcuts: bind a key to each of the three presets, recorded on the settings page
• Auto-translate specific sites: add domains and they translate on load
• Cross-tab continuity: opening a link from a translated page auto-translates the new tab with the same preset
• Translation cache + live cost report: cached content is free next time; a notification shows token count and cost
• Custom glossary with CSV import (two columns: source,translation) with room for hundreds of entries, blocked-word list, and on-page translation editing
• Respects the page's do-not-translate markup: marked names and codes stay untouched and are never sent to the API; icon-font glyphs are never turned into text
• Send to Instapaper: save the whole translated article to Instapaper in one click

[Bring your own API key]

Shinkansen doesn't sell translation as a service — you bring your own Google Gemini API key. Gemini's free tier makes everyday use typically free. Prefer no key? Google Translate works with no setup, and Chinese variant conversion runs offline. Setup steps are in the GitHub repo and the in-app onboarding.

[Privacy]

Shinkansen has no server, no telemetry, no analytics. Every setting lives only on your device:

• Your API key is stored locally in Safari — never synced, never uploaded
• Translation content goes directly from your browser to the endpoint of the engine you chose
• Shinkansen never relays, caches, or logs translation content
• The local cache lives on your device only; clearing browser data wipes it

[First-install note]

After installing, enable the extension in Safari and grant website access:

Settings → Apps → Safari → Extensions → Shinkansen → turn on, set website access to Allow

(The exact path varies slightly by iOS version.)

[System requirements]

• iOS 15 or later / iPadOS 15 or later
• Universal — iPhone and iPad

[Open source]

Open source under Elastic License 2.0 on GitHub — view, learn from, modify, and use it yourself; you may not repackage it (or a modified version) as a hosted or managed service for third parties.