What each platform accepts

How long can a caption be?#

The composer counts against each targeted platform live and warns you before you send, so you rarely need this table — but here it is.

X is the odd one out: it wraps every link in its own shortener, so any URL costs exactly 23 characters no matter how long it looks. The counter already knows that.

Do stories need a caption?#

No — a story has no caption. Neither Instagram nor Facebook has anywhere to print one on a story, so if you post one anyway the text is thrown away and nobody sees it.

So a post that's only going to stories can be sent with the caption box empty: xpost stops asking for one, and the counter says so. Add a feed post or a reel to the same send and the caption is needed again — those two do print it.

If you want words on a story, they have to be in the image or video itself.

How many images can one post carry?#

Every platform publishes a different number of them, and the extras are dropped — quietly, by the platform, with no error. xpost cuts the list to the real limit before sending so what you see in the preview is what gets published.

Pinterest and YouTube take one. If you attach a three-image carousel and target Pinterest, you get a single pin of the first image. The composer flags this on the platform's row, but it surprises people, so: check the preview before you send.

The order you arrange them in the composer is the order they publish in — so the one you want kept is the first one.

Facebook won't take photos and a video in the same post — that's Meta's rule, and its own composer refuses it too. Attach both and xpost publishes the photos to Facebook and leaves the video out, saying so on the platform's row; everywhere else still gets all of it. To put the video on Facebook as well, send it as its own post.

Can I post a picture with no caption?#

On X, Instagram and LinkedIn, yes — a picture on its own is a normal post on all three, and none of them asks for words to go with it. Leave the caption box empty, attach the media, and the Post button stays live.

The caption tools stay where they are, because all three *do* print a caption if you write one. Nothing is asking you to — they're just still there if you want them.

Everywhere else still needs one. Bluesky, Facebook, Threads, TikTok and Pinterest keep asking, and YouTube needs at least a title or your video publishes as "Untitled". Some of those probably would accept an empty caption; they stay on the strict side until each one has been tried for real, because the alternative is a post that fails after we told you it would work.

Sending to several places at once? The caption is shared across all of them, so one destination that needs words brings the requirement back for the whole post.

Which platforms won't take a text-only post?#

These four need something attached: Instagram, TikTok, YouTube, Pinterest. YouTube specifically needs a video.

xpost tells you at the composer rather than letting it fail at delivery time.

What files can I upload?#

Images and video, up to 100 MB each.

Video length is capped differently everywhere — X takes about 140 seconds, Bluesky 3 minutes, Instagram 15 minutes, TikTok 10. Pinterest is the one with a floor as well as a ceiling: 4 seconds to 5 minutes, and it refuses a shorter clip without saying why. The media tray checks the length as you upload and warns you then, rather than minutes later when the delivery fails.

Stories and reels have their own, shorter caps — the placement you pick decides which applies. An Instagram story stops at 60 seconds where a feed video runs to 15 minutes, and a Facebook reel stops at 90 seconds where a Facebook feed video has no practical limit at all. Both refuse anything under 3 seconds.