Why one video rarely fits every network
Vertical 9:16 video is the shared format of Reels, TikTok, Shorts, Threads and Pinterest, but the limits around it differ. Lengths range from 30 seconds on Google Business Profile to 12 hours on YouTube, file size caps from 75 MB to several gigabytes, and a ratio that one network shows full screen can be padded or cropped on another. Checking the target networks before you edit saves a second export.
App limits and API limits
Many networks publish two sets of numbers: what the app accepts and what the publishing API accepts. Scheduling tools, PostBoost included, publish through the API, so the API row is the one that applies when you schedule. Facebook's app takes videos of any length while its Reels publishing API takes 3 to 90 seconds, and Instagram Reels can run 20 minutes in the app but 15 minutes through the API. Rows marked "ads" are the ad placements, which often allow longer and larger files.
Text and safe zones
Each app draws buttons, captions and profile details over the edges of a vertical video. Only Instagram (for Reels ads) and Pinterest publish exact zones, so those are the only rows with numbers; for other networks, keep text and logos near the centre. This page lists no invented safe zones.
How the checker decides
"Does not fit" means the length, the ratio or the file size is outside a limit the source states. "Check" means it fits but the source recommends something else, such as 16:9 for a regular YouTube video, or a long video that only some accounts can post. Codec, frame rate and bitrate are not read from the file, so check them in your editor's export settings.