How to add automatic captions to a video on iPhone

Start with clear audio

Automatic captions are only as accurate as the speech they hear. Record close to the microphone, reduce background noise and speak at a steady pace. Names, numbers and brand terms are the words most worth double-checking afterwards.

• Record in a quiet place or use an external microphone
• Speak one idea at a time
• Choose the correct spoken language before transcribing

Edit the text and the timing

Treat the transcript as a draft. Fix misheard words, split long lines so each caption fits one or two short lines, and adjust the timing where a caption appears too early or lingers. In PromptFy, the grouped captions and the individual word timings stay in sync after every edit.

Pick a style that stays readable

On a phone, contrast and size matter more than decoration. Use a bold font, a color that separates from the footage, and a highlight or box style for busy backgrounds. Word-by-word effects such as karaoke or one-word captions suit fast, energetic delivery, while a classic or minimal style suits a calmer talking-head video.

• Ten presets, from Bold Pop and Highlight Box to Karaoke, Neon and Minimal
• Five bundled fonts, including Montserrat, Poppins and Anton
• Adjustable color, opacity, size and position

Keep captions inside the safe area

Instagram Reels, TikTok and YouTube Shorts place buttons and descriptions over the bottom and right side of the frame. Preview your captions inside the safe area before exporting so nothing important is covered.

Export, then translate if you need to

Exporting creates a new video with the captions burned in, so your original stays untouched. If you publish in more than one language, translate the captions and review the result, or dub the video when you also want translated speech.