How to add auto captions to Instagram Reels and TikTok

Most people start watching a Reel or a TikTok with the sound off. If the first line isn’t written on screen, the thumb moves on before your hook lands. That’s why captions stopped being an extra: in vertical video, they’re part of the edit.

This guide covers how to caption Reels and TikTok with FilmScribe, which size and position to use in 9:16, how to keep captions readable on a six-inch screen, and when the app’s own captions are enough.

App captions or burned-in captions?

There are two routes, and they solve different problems.

If you post one video a week shot on your phone, the app’s captions will do. If you cut a podcast, a sermon or a talk and publish the same clip on three platforms, burning in the captions once in FilmScribe saves work and keeps the same look everywhere.

How to add captions to Reels and TikTok with FilmScribe

When the video comes from a long recording (a church service, a podcast episode, a livestream, a talk), FilmScribe does the clip and the captions in one place.

1. Upload the video or paste a YouTube link

Upload the file (MP4, MOV, MKV, WEBM and more) or paste a YouTube link, including a Short or a livestream. FilmScribe accepts YouTube links; if the video lives on another platform and it’s yours, download the original and upload the file. We transcribe in 90+ languages, with the timing of every word and speakers separated.

2. Pick the clips

FilmScribe suggests up to 60 moments per video, each with a score from 0 to 100 and the type of moment: hook, story, insight, humor, emotion and more. When you upload, you can pick a length range (up to 30 s, 30 to 59 s, 60 to 89 s or 90 s to 3 min) and give instructions in plain text, like “only the parts about family”. If you already know the section, mark the start and end in the transcript.

3. Go vertical

The FilmScribe clip comes out in 9:16 with the camera following whoever speaks, with hard cuts between speakers or a split screen when two people talk. You can also download 1:1 or 4:5 for the feed.

4. Pick the captions

There are 235 styles, from classic TV to word-by-word animation, with 54 fonts. Highlight keywords automatically, build a per-word style and hide sounds like [music]. For a complete look, use one of the 48 templates, which carry the clip title inside the design.

5. Place and review

Drag the captions wherever you want in the preview, above the profile area and away from the buttons. What you see in the FilmScribe preview is what ends up in the video. If you fix a word in the transcript, the fix carries over to the captions on every clip.

6. Download the MP4 and post

Download the clip and post it through each app. On paid plans, there’s no watermark and the original recording quality is preserved; on the trial, clips end with the FilmScribe mark. See the details in animated captions and vertical video.

Caption size in 9:16

Reels, TikTok and Shorts use the same frame: 1080 x 1920 pixels, a 9:16 aspect ratio. Captions have to work on that narrow screen, held in one hand.

In vertical video, the practical limit is the speech itself: if the person talks fast, split into smaller blocks instead of shrinking the type. In FilmScribe, line breaks and size are adjusted right in the preview. If you’re working with an SRT, the subtitle reading speed checker flags blocks that go by too fast.

One rule settles most questions: test on a phone. On a monitor, any font looks big. Send the MP4 to your phone and watch it at arm’s length. If you pulled it closer to read, go bigger.

Where to place captions: the safe zone

The app interface covers parts of the video: tab names and the camera at the top, the like, comment and share column on the right, and the profile name, description and audio at the bottom. Captions under those elements are captions nobody reads.

The areas below are the ones FilmScribe’s free safe zone tool uses, measured on a 1080 x 1920 frame. They’re approximate, because each app changes its interface often.

In practice:

• Captions: centered, between the middle of the screen and the top of the profile area, with at least 60 px of margin on the sides.
• Title or text hook: in the top third, below the app bar.
• The speaker’s face: in the center of the frame, with no caption over the mouth.
• Same video on three platforms: use the tightest margin on each side. TikTok has the tallest bottom area.

Readability: what makes a Reels caption work

Size and position solve half of it. The other half is the text.

1. Blocks that respect the sentence. “God won’t give up / on you today” reads better than “God won’t give / up on you today”.
2. One highlight color, not five. Highlighting the spoken word helps people follow. Changing color, font and size on every word wears them out.
3. Numbers as digits. “3 steps” reads faster than “three steps” on a small screen. Change it in the FilmScribe transcript and the captions follow.
4. No captions over on-screen text. If the video already has a title on screen, move one of them.
5. Leave out sounds that don’t help. In FilmScribe, hide sounds removes [music] and [applause] from the captions.
6. The hook captioned from the first frame. The first line decides whether people stay.

Animated captions: when to use them

Word-by-word animated captions became the standard for podcast, sermon and interview clips because they follow the rhythm of the voice: each word lights up the moment it’s said. They need the timing of every word, not just every sentence. In FilmScribe, that timing comes from the transcript, so the highlight lands at the right instant.

Use animated captions when the video is talk-driven and pace matters: styles like viral, karaoke and boxes. Use a cleaner style, like classic TV, when the content is serious or long, like a testimony or a lesson. The guide on how to add captions automatically explains how the animation works under the hood.

Instagram and TikTok auto captions

Both apps generate captions from audio. On Instagram, the feature sits among the stickers in the Reels editor; on TikTok, under the Captions button in the editing screen. You review the text in the app and post. It’s free and quick, and for a video shot on your phone and posted to one platform, it’s usually enough. Phone editors like CapCut also have auto captions.

The limits show up in a routine: few styles, limited placement, captions viewers can turn off and no file to reuse elsewhere. When the same clip goes to several platforms with your channel’s look, captions burned in with FilmScribe come out the same on all of them. If the captions are already burned in, leave the app’s captions off on the post so the text doesn’t show twice.

Checklist before you post

• The hook is written on screen from the first second.
• Names, numbers and references checked in the FilmScribe transcript.
• No block longer than two lines.
• Captions clear of the profile area and away from the buttons.
• Captions don’t cover the speaker’s mouth.
• Watched on a phone with the sound off.
• The app’s auto captions off, if captions are already burned in.

Common mistakes

• Captions at the very bottom, like on TV. On Reels, the bottom belongs to the interface. Move them up.
• Thin type with no outline. It disappears against a white wall, sky or a light shirt.
• A whole sentence on screen. In 9:16 with a large font, a long block covers half the video.
• Posting without proofreading. A misspelled name is what people comment on most. Fix it in the FilmScribe transcript before you download.
• A different style on every video. Pick one style in FilmScribe and use it on every post: that’s how people recognize you.