Ultimate Smart Subs
The right subtitles. Found or created. Aligned for you.
Ultimate Smart Subs searches several subtitle sources at once, puts the subtitle that best fits your video file first, aligns its timing when needed, and translates one for you only when no human subtitle exists. It works for movies and series, in 31 languages today, with more languages and local sources added as the community asks for them.
Why try it
- The first option is the best one. Every language gets an ⚡AUTO row: the subtitle most likely to be in sync with your exact release (file hash, release name, frame rate). Up to two alternatives sit right below it.
- Human translations come first. A subtitle marked as human-made is preferred over a machine translation. A release-matched file only jumps ahead when it is also a human translation.
- Clear labels, no guessing. 👤 human, 🤖 AI and 📄 unknown origin, plus the source and translator, are shown the same way on the setup page, in the subtitle list and in a short note inside the subtitle.
- Timing fixed for your release. The addon checks each subtitle's timing against your video release and corrects it when it is off. When it is not confident, it leaves the timing alone instead of guessing.
- Translation only when nothing exists. Bring your own free Gemini key (no card) or DeepL key. Translations can be shared, so a film translated once is ready for the next viewer without spending anyone's quota. Gemini works out who is speaking to whom, so gendered grammar and forms of address stay consistent within a scene.
- Learn a language while you watch. Optional "Second language under each line" shows the matching line from a second language in italics under every subtitle.
- No empty lists. If your language has nothing for a title, you get its regional variant (e.g. Portuguese ↔ Brazilian Portuguese) or an English subtitle instead of a blank menu, clearly labelled.
- Local sources for each language. Besides the big international databases, the addon also searches sites made for a specific language, such as AltyaziDB and turkcealtyazi.org for Turkish and Subs.ro for Romanian. More country and language-specific sources will be added as users suggest them.
- Series aware. Picks the right episode from season packs and catches mismatched episode numbering between releases.
- Private by design. No account. Your settings and keys are stored encrypted inside your own install link. No ads are inserted into subtitles. The only exception: on a day the free server's storage quota runs out, the short playback note (if notes are on) says so once per installation and includes the optional support link.
Sources
| Source | Needs |
|---|---|
| OpenSubtitles V3 | Nothing (global) |
| OpenSubtitles.com | Your API key (free tier available) |
| SubDL | Your API key (free tier available) |
| SubSource | Your API key (free tier available) |
| Subs.ro | Your API key (Romanian) |
| AltyaziDB | Nothing (Turkish) |
| turkcealtyazi.org | Your API key (Turkish) |
Know a good subtitle site for your language or country? Suggest it, and we will look at adding it as a local source!
Languages
Today: Turkish, English, German, French, Spanish, Italian, Portuguese, Portuguese (Brazil), Arabic, Russian, Ukrainian, Polish, Dutch, Greek, Czech, Hungarian, Romanian, Serbian, Bulgarian, Swedish, Danish, Finnish, Norwegian, Japanese, Korean, Chinese, Vietnamese, Indonesian, Malay, Thai and Persian.
This list is not final. If your language is missing, ask for it and it will be added.
How to install
- Click Install (or open the configure page). Setup opens first.
- Pick your subtitle languages. OpenSubtitles V3 works with no key; add free keys for more sources if you like.
- Optional: turn on translation and paste a Gemini key from Google AI Studio (free) or a DeepL API Free key.
- Press Install in Stremio.
- While watching, choose Ultimate Smart Subs ⚡AUTO in the subtitle menu. Stremio may pick an embedded or another addon's subtitle first; the addon cannot override that choice.
Changing settings creates a new install link; install it again. Keep the link private because it contains your keys.
Good to know
- The hosted server runs on a free plan. After a quiet period, the first request can take up to a minute.
- Timing correction is automatic and cannot guarantee perfect sync for every release.
- Human/AI labels come from the source's own metadata. "Unknown" never counts as human.
- Machine translations are always labeled and are not professional translations.
Help it grow 🙌
This addon improves with every viewer who uses it:
- Share translations. "Reuse translations other users already made" (translation step of the setup page) is on by default. Leave it on: you get translations others made, and every film you translate becomes free for everyone else. Only subtitle text is shared, never your keys or files.
- Bring your language and your local sites. Missing a language, or know the subtitle site everyone in your country uses? Suggest it and it can become a built-in source.
- Tell us what to improve. Got a subtitle that was out of sync? Write to us at [FEEDBACK CHANNEL] with your device, language, title/episode and which row you picked. Never share your API keys or install link.
Every suggestion is read, and user feedback decides what gets built next.
☕ Support development (optional, nothing is locked behind payment)