POST SIZES · CHECKED 6 OCTOBER 2026

Eight channels. Eight sets of rules.

The image sizes, carousel counts, video lengths and caption limits for every channel, each with its source. Or let an AI CMO make every post at the right size for all eight.

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At a glance.

Channel	Feed image	Vertical video	Images a post	Text
LinkedIn	3:1 to 4:5 · 1,080 px wide	1:2.4 to 2.4:1 · 15 min	20, or a PDF	3,000
X	Not stated (ads: 1200 × 1200)	Up to 2 min 20 s	4	280 (weighted)
Instagram	4:5 or 3:4 · 1,080 px wide	Reels 9:16 · 1080 × 1920	10 through the API	2,200 · 5 hashtags
TikTok	Photo mode · up to 1080p	9:16 · 60 min upload	35	4,000 (2,200 via API)
YouTube	Thumbnail 1280 × 720	Shorts: vertical or square, ≤ 3 min	—	Title 100 · description 5,000
Facebook	JPG under 15 MB (reported)	Reels 9:16 · 1080 × 1920	Not stated	63,206
Threads	JPEG/PNG ≤ 8 MB · 1,440 px	Up to 5 min · 1 GB	20	500
Bluesky	Any shape · up to 2 MB	Up to 10 min · 300 MB	4, or 1 video	300

Each channel's page has the details, the exceptions and the sources.

LinkedInLinkedIn image sizes, multi-photo and PDF carousel limits, video length and file size, and the 3,000-character post — sourced and dated.
X (Twitter)X image and GIF limits, how many photos a post takes, video length with and without Premium, and the weighted 280-character count — sourced.
InstagramInstagram feed sizes (4:5, 3:4, 1.91:1), carousel rules, Reels specs and the 5-hashtag cap — with the source for every number.
TikTokTikTok's vertical 9:16 size, upload length, photo mode's 35 photos, and what a scheduling tool is held to through TikTok's API — sourced.
YouTubeWhat counts as a YouTube Short, upload limits, the bitrate YouTube recommends, the 1280 × 720 thumbnail and the title and description limits — sourced.
FacebookFacebook image advice, why every video is now a Reel, the Reels specs a scheduling tool is held to, and the 63,206-character post — sourced.
ThreadsThreads image and video limits, the 20-item carousel, and the 500-character post where an emoji counts as several — from Meta's Threads API docs.
BlueskyBluesky's 4 images or one video, the 2 MB image and 10-minute, 300 MB video limits, and 300 characters — read from Bluesky's own open-source code.