Whole folders at once
Every video’s subtitles are found and matched to it, by name, by episode number or from a Subs folder, and each video gets only the translations it’s missing.
SubStantial for Mac
Translate whole folders of subtitles
SubStantial finds the subtitles for every video in your folders, translates them with the language model you choose, and saves each translation next to its video, named so media players find it.
Free · macOS 14 or later · Apple silicon and Intel · SRT, VTT, ASS and SSA
How it works
Add the folders your films and shows are in. SubStantial works out what each video is missing, and fills the gaps.
- 1
Add your folders
Drop them on the window. Every video is listed with the languages of its subtitles, whether they’re next to it, in a Subs folder or inside the video.
- 2
Choose a language
Videos without subtitles in it are checked for you. Each is translated from its best subtitles, English first, with forced subtitles translated separately.
- 3
Translate and check
Each translation is saved next to its video. Open the video to watch it with the original alongside, and fix any line.
Made for real libraries
Subtitles come in every format, encoding and naming style, next to videos and inside them. SubStantial handles the awkward parts.
Subtitles from speech
For a video without subtitles, Whisper writes down what’s said, on your Mac. Give it the names people say, and it spells them right.
Tracks inside videos
The subtitle tracks inside MKV and MP4 files are listed with the files next to them, and translated the same way. Nothing is ever written into a video.
Proofreading
Your language model fixes typos, grammar and misheard words. Each change is highlighted, with what it said before, for you to keep or undo.
Names media players expect
Subtitle files are renamed after their videos and moved next to them, the way Plex, Jellyfin, Kodi and Infuse look for them. You see every rename first.
Every format and encoding
Unicode, and the older encodings for European, Cyrillic, Greek, Turkish, Hebrew, Arabic, Thai, Japanese, Chinese and Korean text, are detected automatically. Italics, positions and styles are kept.
- SubRip (.srt)
- WebVTT (.vtt)
- SubStation Alpha (.ass, .ssa)
Watch, compare and fix every line
Each video opens in its own window: the translation over the picture, the original alongside, and every subtitle on a timeline of the sound. Edit a line, drag it to retime it, and undo anything.
The model is up to you
Translate with a provider’s model, or with one SubStantial runs on your Mac. Either way, only the text of each subtitle is sent, never its times, so nothing can slip out of sync.
With a provider
OpenRouter and OpenAI offer the strongest models, through your own account, with your API key kept in your keychain. Ollama and LM Studio run models on your Mac or network, and any OpenAI-compatible service works too.
- OpenRouter
- OpenAI
- Ollama
- LM Studio
- OpenAI-compatible
On your Mac
Download Google’s open Gemma 4 model, and translate with it on your Mac. Your subtitles never leave it, and there’s nothing to pay.
- Gemma 4 E4B 4.6 GB, for Macs with 16 GB of memory
- Gemma 4 26B 14.6 GB, for Macs with 32 GB; translates better
On an M4 Pro, either translates an hour of dialogue in about five minutes.
The details, handled
- Sentences kept whole, with names and forms of address consistent across a film
- Italics, positions and styles kept, and long lines broken in two again
- Lines a model skips or runs together spotted and asked for again
- Lines worth checking marked, and a translation in the wrong language reported
- Forced and SDH subtitles translated separately, keeping their tags
- Nothing replaced without asking, twice, and SubStantial’s own files marked as its own
- Saved as UTF-8, with a byte order mark where older TVs need one
- In English, Japanese, Korean, French, Spanish and Brazilian Portuguese
Your subtitles go only where you choose. SubStantial collects no data. Subtitle text goes only to the provider you pick, and you’re asked first. With a model on your Mac, and when making subtitles from speech, nothing leaves it.
Privacy policy
Get SubStantial
Free on the Mac App Store, for macOS 14 or later on Apple silicon and Intel Macs. Providers such as OpenRouter and OpenAI charge for what you translate, through your own account.
Questions
How do I translate an SRT file on a Mac?
Add the folder it’s in to SubStantial, choose the language and click Translate. The translation is saved next to the original, named so media players find it: Movie.en.srt gets a Movie.es.srt. A subtitle file without a video is translated the same way.
Is SubStantial free?
Yes, from the Mac App Store. Translating with a model on your Mac, or with Ollama or LM Studio, costs nothing. OpenRouter and OpenAI charge for what you translate, through your own account.
Which subtitle files does it work with?
SubRip (.srt), WebVTT (.vtt) and SubStation Alpha (.ass, .ssa) files, in Unicode or any common older encoding, and the text subtitle tracks inside MKV, MP4 and other videos. Blu-ray and DVD subtitles are pictures of text, so they’re listed but can’t be translated.
Where do my subtitles go?
Only the text of each subtitle goes to the language model, numbered: never the file, its times or your videos. With a provider, it goes to that provider, and SubStantial asks you first. With a model on your Mac, and when making subtitles from speech, nothing leaves your Mac.
Will it replace my subtitles?
Not without asking. Translations are saved as new files next to the originals. A video that already has subtitles in the language is skipped unless you choose to replace them, and you’re asked again, with the files named, before anything is replaced.
Can it make subtitles for a video that has none?
Yes: right-click the video and choose Create Subtitles…, or click Create Subtitles in its window. Whisper writes down what’s said, on your Mac, and the subtitles can then be proofread or translated.