The Social Magnum blog
Notes from building on all social networks — the platform rules, the publishing playbooks and the API behaviour nobody documents. Every figure here was checked on a live account.
Facebook Post Size: The Ratios Facebook Actually Keeps
Four different answers sit on page one because Facebook publishes no size for an organic feed post. The page ranking first is documentation for ads.
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Facebook Cover Photo Size: Desktop and Mobile Disagree
Facebook's own help page gives three numbers that do not reconcile: a 16:9 desktop display, a 2.4:1 mobile display, and an 851 × 315 file that matches neither.
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Instagram Reel Size: 1080 × 1920, and the Cover You Cannot Redo
The video is the easy part. The cover is a separate 420 × 654 image, it is what your profile grid is built from, and Instagram says you cannot change it once it is uploaded.
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LinkedIn Banner Size: 1584 × 396 for Profiles, 1512 × 256 for Pages
Two different images with two different shapes. The Company Page cover is 1512 × 256 — and the three figures circulating instead of it are not wrong in the same way.
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Instagram Story Size: 1080 × 1920, and What the Interface Covers
The dimensions are settled — every page agrees on 1080 × 1920. What is not settled is whether that is 9:16 or 16:9, and how much of your frame Instagram's own interface sits on top of.
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Instagram Post Size: 4:5, 3:4, and the Number Most Guides Get Wrong
Instagram accepts 1080 wide at any height from 566 to 1440 pixels. The tallest post is 1080 × 1440, not the 1080 × 1350 nearly every guide quotes — including one ranking on page one.
Read the articleWe write this down because we hit it ourselves.
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