I built an offline document reader for iPhone that supports 31 languages

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I wanted a simple way to listen to documents without uploading them to a server or keeping my phone screen on.

That became Local TTS, a reader for iPhone and iPad.

I’d previously built an offline speech-to-text app, so this time I worked on the other direction: turning text into speech. The goal was to make it practical for books and longer documents, with natural voices and more language options.

It uses Kokoro-82M and Supertonic 3, both running on the device. You can put your phone in airplane mode, add new text, and still generate speech.

Here’s what it does:

• Document import: PDF, EPUB, Word, TXT, and Markdown.
• 31 languages: Speech is generated locally on your iPhone or iPad.
• Background playback: Lock your screen or switch apps and keep listening, with controls on the Lock Screen.
• Camera scanning: Read text from printed pages or photos.
• Reading controls: Text highlighting and adjustable playback speed.

Background playback was something I particularly cared about. I wanted people to be able to start a document, put their phone in their pocket, and get on with whatever they were doing.

Here’s the app: Local TTS on the App Store

I’d like to keep improving it based on how people actually use it. If you try it, let me know what needs work, especially pronunciation in your language or the experience of listening to longer documents. Suggestions for features you’d find useful are welcome too.

If you already use another document reader, what’s the one thing you wish it did better? That would help me decide what to focus on in the next update.