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.
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.
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YouTube Banner Size: One Image, Four Different Crops
2560 × 1440 is the figure everyone quotes. The minimum, the safe area and the 6 MB cap are on YouTube's page too, inside a collapsed section, and the safe area it gives is not the one guides repeat.
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YouTube Thumbnail Size: What Changed, and Whether Your Old Files Still Work
YouTube now recommends 3840 × 2160, but most of page one — and Google's own AI Overview — still says 1280 × 720. Here is what actually changed, and why your existing thumbnails are fine.
Read the articleWe write this down because we hit it ourselves.
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