Your videos stay with you.

Undertekst is an iPhone app by Peter Theill. Updated 4 October 2026. Contact: support@undertekst.theill.com

Your videos stay on your phone

Undertekst makes a copy of the video you pick in the app's own storage on your iPhone. The speech is transcribed on the phone with Apple's speech recognition or, if you've downloaded it, with Whisper. The subtitles are burned into a new video on the phone. Videos, sound and text are never sent anywhere.

When you save, Undertekst asks for permission to add the new video to your photo library. The app can't see your other photos and videos.

Speech models

For some languages, iOS downloads Apple's speech model the first time, directly from Apple. If you choose Whisper in Settings, the app downloads the model from Hugging Face. Those are the only times the internet is used, and nothing about you or your videos is sent along.

No account and no tracking

Undertekst has no account, ads, analytics or tracking SDKs. The App Store label is “Data Not Collected”. If you delete the app, your projects are deleted too.

Purchases

If you buy Supporter, Apple handles the payment. We never get any payment details.

Support emails

If you write to support, we use what you send to answer you. Mail is handled by our email providers. Write if you'd like your correspondence deleted.

This website

Cloudflare hosts this website and processes technical request data, such as IP address and browser, to deliver and protect it. The site has no ads, analytics or tracking pixels. See Cloudflare's privacy policy.