Carousels on Threads and TikTok: Sizes and What Works
Threads and TikTok both accept image carousels, and both reward a slightly different cut of the one you made for Instagram: Threads wants fewer slides and a text-first post around them, TikTok wants a 9:16 vertical set with music and a hook that reads like a video title. Neither needs a redesign; they need a re-export and a rewritten opening line. Here are the specifications and what changes on each.
Threads
What it accepts. Up to 20 images per post, any common ratio, and a text post of up to 500 characters that the images sit under. Images display in a horizontal strip in the feed, swiped like Instagram’s.
What is different. The feed is mostly text, so an image carousel stands out and the text post above it does the hook’s job. People read the post, then swipe. A 4:5 set exported for Instagram works as is; square works too.
What works.
- Shorter sets. Three to six slides. The Threads feed moves faster than Instagram’s and a long swipe gets abandoned.
- The text post is the hook. Write it as a one-line claim or question, then let the first slide repeat it in large type. The two together are the hook.
- Replies as the close. Threads is a reply network. End with a question in the text post and make the last slide ask the same question; comments carry the post further than saves do here.
- Reposting an Instagram carousel. Same files, shorter text, and cut to the strongest six slides. How many slides a carousel should have covers how to cut without losing the argument.
TikTok photo posts
What it accepts. Up to 35 images, displayed as a swipeable or auto-advancing set with music. The vertical 9:16 (1080 by 1920) format fills the screen; other ratios are letterboxed on a background.
What is different. Photo posts are shown to non-followers the way videos are, so a photo carousel on TikTok is a reach format, not a saves format. The audio matters: a trending sound on a photo post behaves like a video with that sound. Text on slides is read with the sound playing and the caption overlaid at the bottom.
What works.
- 9:16 slides. Re-render the carousel at 1080 by 1920 rather than letterboxing the 4:5 version. Karou renders 9:16 from the same slides, with the layout adjusted for the taller frame.
- Bigger text, fewer words. Slides auto-advance in some views, so each slide has about two seconds. A title and one short line per slide. How much text fits on a slide gives the counts; cut them by a third for TikTok.
- The hook reads like a video title. “3 pricing mistakes (I made all of them)” works; a quiet editorial hook does not.
- Keep the bottom clear. The caption, the sound and the buttons overlay the lower part of the screen. Keep the slide’s text in the upper two thirds.
- The close asks for a follow. Saves exist, but TikTok’s loop is reach then follow.
Side by side
| Threads | TikTok photo post | ||
|---|---|---|---|
| Ratio | 4:5 (1080 x 1350) | 4:5 or 1:1 | 9:16 (1080 x 1920) |
| Max slides | 20 | 20 | 35 |
| Sweet spot | 6 to 10 | 3 to 6 | 5 to 8 |
| Hook lives in | Slide one | The text post, repeated on slide one | Slide one, as a video-style title |
| Sound | No | No | Yes, and it matters |
| Best ask | Save | Reply | Follow |
| Reach | Followers first | Followers first | Non-followers |
One carousel, three exports
The cheapest way to be on all three is to write the carousel once and export it three ways:
- Instagram: 4:5, six to ten slides, the close asks for a save.
- Threads: the same 4:5 files, cut to the six strongest, with the text post carrying the hook and asking a question.
- TikTok: 9:16 re-render, five to eight slides, bigger text, a sound, the close asks for a follow.
With Karou the three exports are one create call for 4:5 and one edit call with format: 9:16 for the vertical set; the slides stay the same, the layout adapts, and both ZIPs come back in the chat. The structure of the carousel itself does not change between networks; carousel post ideas and brand consistency apply to all three.
What does not transfer
- Captions in the slide text. On TikTok the caption overlays the slide; a slide that needs the caption to make sense fails there.
- Long stories. A ten-slide confession works on Instagram, gets abandoned on Threads, and auto-advances past its beats on TikTok. Keep stories for Instagram and LinkedIn.
- Links. None of the three make slide links clickable. Threads allows a link in the post text; TikTok allows one in the bio.
FAQ
Should I post the same day on all three?
It does not matter for the algorithm; it matters for your routine. Posting all three from one render in one sitting is the routine most people can keep.
Does Threads show the first slide in the feed?
It shows the images in a strip under the text, with the first most prominent. The text post is still what people read first.
Can TikTok photo posts be square?
Yes, letterboxed on a blurred or solid background. They look like what they are: a repost. 9:16 is worth the re-render.
Do photo posts on TikTok get fewer views than videos?
They get shown through the same feed; a good hook and a current sound matter more than the medium.