Why social image sizes differ: the method behind one big table
'How big is this platform's cover' is a question creators look up daily. The answer is more than one number — behind each size is a platform's own display and crop logic. Understand it and you know where to put the text.
Sizes are dictated by how the feed displays
A platform's cover size isn't a designer's guess — it's back-derived from its feed layout. Xiaohongshu is a two-column masonry feed where vertical images dominate, so 3:4 (even 4:5) covers win; YouTube is a 16:9 horizontal player, so thumbnails are naturally 1280×720.
Grasp this and you stop memorizing: a platform built on fullscreen vertical playback (Channels, Douyin) will always favor tall covers; a horizontally laid-out platform (Bilibili, YouTube) will favor wide ones.
Safe zones: right size, right position
Knowing the size isn't enough. A WeChat header is 900×383, but when shared into a chat the system crops the middle to a 1:1 thumbnail — put your headline on the left and only half of it survives the share.
So every size deserves a 'safe zone' note: where key text goes, what gets cropped. Poster Cat's size dataset tags safe-zone notes for the tricky ones (WeChat header, Facebook cover, Pinterest pin) so you place text correctly the first time.
A maintained dataset beats searching for stray numbers
Search 'WeChat cover size' and you get a pile of contradictory, stale numbers — nobody updates them after a redesign. Poster Cat organizes the exact pixels for WeChat, Xiaohongshu, video, general and print into one structured dataset, each size carrying its ratio, group and safe-zone note, maintained as platforms change.
More importantly the dataset isn't there to read — it drives the tools. Click any size in the size guide and the matching canvas opens at those exact pixels, type and it's done. The numbers and the tool share one source, so they never disagree.
How to use the table
Decide the platform and format (cover / thumbnail / vertical story), find the matching entry in the size guide, note the ratio and safe zone, then jump into the right tool and type.
If you're reposting one image across platforms (same graphic to Xiaohongshu and to a feed), make the master at the tallest ratio (usually 4:5 or 3:4) and crop down for the rest — cropping large-to-small loses nothing, scaling small-to-large goes soft.
Make it now
Frequently asked questions
What's the WeChat cover size, and why does it change after sharing?
The header is 900×383. When shared into a chat the system crops the center to a 1:1 thumbnail, so keep important text in the central safe zone or it gets cropped on share.
Why do platform cover sizes differ so much?
Because feeds display differently. Fullscreen vertical platforms (Channels, Douyin) want tall covers, horizontal players (YouTube, Bilibili) want wide ones, and two-column masonry (Xiaohongshu) prefers 3:4 verticals.
I want one image on several platforms — what about sizes?
Make the master at the tallest ratio (usually 4:5 or 3:4) and crop down for other platforms. Cropping large-to-small keeps content; scaling up goes soft.
Updated · Poster Cat team