Field notes
Playbooks, teardowns and the occasional argument — everything we have learned helping creators grow across every major platform.
The answer is arithmetic from your canvas and your font size, and the thing that actually breaks a quote card is a last line with one word on it.
No platform limits the text on a carousel image. What limits it is whether anybody can read it at feed size, which makes the answer arithmetic rather than a rule.
Instagram writes an automatic description for every image whether you do or not. Yours replaces it, you get 100 characters, and the field is three taps deep.
Instagram stores 100 characters, LinkedIn 120, X 1,000, Bluesky 2,000. A description written for one and pasted into another is cut mid-sentence, and nothing tells you.
Upload 2560×1440. Design for 1546×423 — the window every phone shows, which is 17% of the file. Four devices crop the same image four different ways.
Spotify publishes album and artist images at 640, 300 and 64 pixels. There is no original behind the 640 — every 'HD Spotify cover art' result is upscaling the same file.
Apple's public directory hands out a 600-pixel copy. The 3000×3000 the publisher submitted is at the same address with one number changed.
Upload a square image of at least 600×600. That is also the largest Twitch stores — and the page only ever publishes the 300, which is why avatars look soft when reused.
The picture rendered fine when you pasted it and is a broken icon now. The expiry was in the URL the whole time — here is how to read it.
Bluesky is the one platform that will simply tell you what is on a post. You get every image, the alt text, and the file exactly as it was uploaded.
Threads answers a signed-out request honestly, which makes it one of the easier platforms to get a picture out of. Two details are worth knowing first.
Two different links, two different routes. A post gives you what its link card publishes; a Page gives you its picture at the size Facebook stores.