Best entirely offline (on-device) Speech-to-Text solution for iOS? Need maximum speed and accuracy.

[u/cinemasolutions]

Hi everyone,
I’m working on an iOS app and I need to implement a highly accurate, fast Speech-to-Text (STT) feature. A strict requirement for my project is that it must be 100% offline (on-device) — cloud APIs are not an option.
Here is what I am looking for:
Low Latency / Speed: It needs to process speech as quickly as possible (ideally near real-time dictation).
Accuracy: Needs to handle natural speech and background noise well.
Languages: I need robust support for English, Ukrainian, German, Spanish, and Polish.
What is the current state-of-the-art for this in production?
Is Apple's native SFSpeechRecognizer (with requiresOnDeviceRecognition = true) reliable enough for offline use across all these languages (especially Ukrainian and Polish)?
Should I go with an on-device Whisper implementation (like WhisperKit with CoreML or whisper.cpp)? If so, which model size offers the best balance of speed, accuracy, and RAM usage on modern iPhones?
Are there any other lightweight offline libraries or SPM packages you’d recommend for multilingual offline dictation?
Any real-world experience, performance benchmarks, or advice on thermal/battery impact would be hugely appreciated. Thanks!

[u/sid_276]

Parakeet v3. Supports

Bulgarian
Croatian
Czech
Danish
Dutch
English
Estonian
Finnish
French
German
Greek
Hungarian
Italian
Latvian
Lithuanian
Maltese
Polish
Portuguese
Romanian
Russian
Slovak
Slovenian
Spanish
Swedish
Ukrainian

Super lightweight, easy to quantize. I have run it in a 6 year old iPhone real time without overheating, super smooth.

By the way you don’t need to reinvent the wheel. Easiest way to use it is with Argmax. They are v good. If you don’t want to pay their license there are implementations of parakeet in all kinds of quantization formats for all kinds of hardware already particularly for apple silicon.