zerotoneroAcademy · Lesson 7 of 9 · 7 min
Captions, text overlays and sound
Plenty of people watch muted, and the rest need to hear you clearly. Make your promo work with sound off and sound good with it on.
Design every promo to survive two audiences: people watching with sound off and people watching with sound on. Sound-off viewers need captions and text overlays to follow along. Sound-on viewers need a clear voice that is not fighting the music. If your video only works for one of them, you are throwing half your views away.
Captions are the words of your A-roll on screen. Keep them short: a few words per line, one or two lines at a time, timed to the speech. Large, high-contrast text with an outline or a background box so it reads over any footage. Most editing apps and the platforms themselves can auto-generate captions, but always proofread them. A mangled app name in your captions looks careless, and auto-captions love mangling app names.
Text overlays are different from captions. They are headlines, not transcripts: '2 taps', 'Rent: in 4 days', 'Free on iOS'. Use them to land the hook, label a key moment, or repeat the CTA. One idea per overlay, on screen long enough to read twice. If you have to choose between a caption and an overlay fighting for space, simplify one of them.
Placement matters. Short-form apps draw their own interface over your video: usernames and descriptions near the bottom, buttons down the right side, tabs at the top. Keep captions and overlays in the middle area of the frame, away from those edges. Most editors can show a safe-zone guide, and it is worth checking the current guides for each platform since the interfaces change.
For sound, voice comes first. Record in a small, soft room (a closet full of clothes works wonders), close to the mic, away from the fan. If you add music, duck it well under your voice. A good test: listen on your phone speaker at low volume. If you have to strain to hear the words, the music is too loud. Use only music you have the rights to, or the platform's built-in licensed library.
Small sound effects (a tap, a whoosh on a transition, a soft ding when a goal completes) can make UI moments feel tactile. Use them sparingly and keep them quieter than the voice. They are seasoning, not the meal.
Key points
- Design for sound-off and sound-on viewers at the same time.
- Captions transcribe; overlays headline. Proofread auto-captions, especially your app name.
- Keep text in the middle of the frame, clear of platform UI at the top, bottom and right.
- Voice first: record close and quiet, duck music well under speech.
Good: Works muted, sounds clean
A made-up language-flashcard app. Captions in the safe zone, headline overlays, and music ducked under a clear voice.
- 1s Hook overlay sits mid-frame, away from the username and buttons.
- 4s Captions run throughout: short lines, outlined, proofread app name.
- 9s One quiet tap effect, well under the voice.
- 12s Music ducked low; the voiceover is clear even on a phone speaker.
Bad: Loud music, no captions, text under the buttons
Same app. Muted, it is a silent mystery. Unmuted, the music buries the voice. The overlay sits right where the platform UI goes.
- 1s No captions and no overlay: muted viewers see a face moving its mouth.
- 5s Music sits as loud as the voice. Words get lost on a phone speaker.
- 8s Five-card feature is never named on screen, so muted viewers miss the point.
- 16s CTA text placed where the username and description will cover it.
Common mistakes
- No captions, so the video means nothing on mute.
- Publishing auto-captions without proofreading them.
- Music mixed as loud as (or louder than) the voice.
- Placing text at the very top, bottom, or right edge where platform UI covers it.
- Overlays crammed with full sentences instead of short headlines.
- Using music you do not have the rights to.