Threads carousel limits: 2 to 20 items, images and video

A Threads carousel through Meta's API holds at least 2 and up to 20 items, and each item can be an image or a video. Images are JPEG or PNG up to 8 MB with a width of 320 to 1440 pixels in sRGB. Read 2026-09-29.

What are the carousel and image limits?

Meta's page lists video specs separately (MOV or MP4, H.264 or HEVC, up to 300 seconds); the carousel line only says items can be images, videos or a mix.

How do I make a matching set of images?

Use POST /v1/images with one aspect_ratio for every slide so the carousel does not crop unevenly. 4:5 and 9:16 are in the image docs' ratio list; check GET /v1/images/models for the model you pick. With openai/gpt-image-2.5, use image_size (both edges a multiple of 16), e.g. 1088x1360, which is 4:5 and inside 320 to 1440 wide.

1088 x 1360 = 1,479,680 pixels, inside the model's 655,360 to 8,294,400 range.

curl -X POST https://api.sume.com/v1/images \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "openai/gpt-image-2.5",
    "prompt": "Slide 1 of 5: minimalist poster, five steps to brew pour-over coffee, warm palette",
    "image_size": "1088x1360"
  }'

Can video items be Sume clips?

Yes. Generate each with the same aspect_ratio. Note that no Sume video model lists 4:5, so mixing 4:5 images with video means video at 9:16 or 1:1, or cropping with POST /v1/video-filter (crop op takes fractions of the frame).

What are the limits of this answer?

Sume does not publish to Threads or check the 8 MB image limit.