The numbers each platform actually uses.
Sizes, lengths and limits for Instagram, Threads and Bluesky, taken from their developer documentation and checked in October 2026.
Instagram image sizes for posts and carousels
Instagram image sizes, aspect ratios and limits for feed posts and carousels: JPEG, up to 8 MB, from 4:5 to 1.91:1, carousels of up to 10. Checked Oct
ReadInstagram Reels specs that never get refused
Instagram Reels video specs through the API: MP4 or MOV, H.264 or HEVC, AAC audio, 23 to 60 fps, up to 1920 px wide, 3 seconds to 15 minutes, up to 30
ReadThreads limits: characters, photos, videos
Threads limits through the API: 500 characters, JPEG or PNG photos up to 8 MB, carousels of 2 to 20, videos up to 5 minutes and 1 GB. Checked October
ReadBluesky limits: 300 characters, 4 photos
Bluesky post limits: 300 characters, up to 4 images of up to about 976 KB each, one video of up to 3 minutes and 100 MB, clickable links and hashtags.
ReadOfficial API or browser bots?
Why the way an app posts for you matters.
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