Paste a post and see what your network actually sees, including the exact spot LinkedIn hides the rest behind "...more". Desktop and mobile. Free, no signup.
In the feed, LinkedIn shows roughly three lines on desktop, about 210 characters, and closer to 140 on mobile before hiding the rest behind "...more". Line breaks count against you too, so a post that opens with several short lines folds even earlier. Most readers never click through. Whatever sits below that fold, most of your audience simply never reads.
LinkedIn watches what readers do with your post. Click "...more"? Good sign. Linger a while? Better. A hook that survives the fold earns those clicks, and the algorithm responds by showing the post to more people. So check what actually fits above the line before you publish, on a phone, not just your monitor. That's where most of your readers are.