GUIDE · SHORT VIDEO
A carousel you already made is a short video waiting to happen: the slides are the pictures, and a line of voice per slide carries the story. Here is how to do it so the slides follow the voice — and how to have it made every time you post.
THE SHORT ANSWER
Write two to four spoken sentences for each slide (the slide states it, the voice explains it), record them, then place each slide in a video editor for as long as its line lasts, with music low underneath. Export a vertical video — 1080 × 1920 is common practice — and upload it as a Reel, a TikTok and a YouTube Short. Shorts can run up to three minutes; Reels take any shape from 1.91:1 to 9:16.
| Channel | Shape | Length |
|---|---|---|
| Instagram Reels | From 1.91:1 to 9:16; at least 720 px | Short is best for reach; see Instagram's current upload limit |
| YouTube Shorts | Square or vertical | Up to 3 minutes (uploads since 15 October 2024) |
| TikTok | Vertical | Uploads up to 60 minutes; up to 10 recorded in the app |
1080 × 1920 (9:16) is the common working size, not a platform rule.
Write a line per slide
Two to four spoken sentences a slide, about 30–55 words: the slide states the point, the voice explains why or how. The first line hooks; the last one asks for the action.
Record the voice
Record each line on its own (a phone in a quiet room is fine) or use a text-to-speech voice. Separate clips make the timing easy.
Lay the slides on the timeline
In any video editor, place slide one, then its voice clip under it, and stretch the slide to the clip's length plus a short beat. Repeat for every slide.
Add music, low
Put a track under the whole video at a low level so it never fights the voice.
Export vertical
Export an MP4 at 1080 × 1920. A 4:5 carousel can sit in the middle with bands above and below, or be redrawn at 9:16.
Upload to each channel
Post it as a Reel, a TikTok and a YouTube Short, each with a caption written for that channel.
Most slide videos fail because every slide gets the same few seconds — too short for a dense slide, too long for a simple one. Record the voice first and let each slide last as long as its line: the viewer hears the explanation while the slide is on screen.
WITH PAPERFLIGHT
When PaperFlight's Writer writes a deck, it also writes the spoken line for each slide. The voice is made first; each slide then lasts its line plus a beat, music sits underneath at a low level, and the one video goes to Instagram, TikTok and YouTube — at the feed size with bands, or full-screen 9:16 if you choose.
PaperFlight is an AI CMO with its own team: it plans the week, writes and designs every post in your brand, publishes it to eight channels and learns from the results. 7 days free, no card.
Last checked 6 October 2026. Platforms change their limits and features often — check their help pages before you rely on a number.