The attacking team passes from one side to the other, and the defending team seems to move as a single dark band. A low block is easier to understand when you stop following only the ball and watch how that band changes shape.
Low describes the team’s position closer to its own goal. Compact describes the distances within the shape. Those are related choices, but they are not identical: a team can defend deep while leaving gaps between players or between its lines.
Follow the player furthest from the ball
When the ball moves towards one touchline, look at the defender or winger on the opposite side. Do they move inwards to protect central space, or remain wide near an opponent? That choice helps explain where the next pass might go.
Now watch the space between midfield and defence. An attacker standing there may appear unmarked on television, but the pass into them might be difficult because another defender blocks the route. Space on the screen is not automatically usable space on the pitch.
Notice what a switch changes
A quick switch of play can make the block travel further. Watch whether the receiver controls the ball before the defenders arrive, and whether a supporting runner offers an option beyond a simple return pass. A slow switch may allow the entire shape to reset without much disruption.
For your next match, follow three possessions with one question: which pass made the defending team change its spacing? It could be a pass backwards that draws a player out, a diagonal towards the far side, or a ball into a forward who can protect it.
There is no single pass that defeats every low block. Player quality, game state and the defending team’s decisions all matter. Watching width gives you a more useful explanation than assuming the side with more possession must be attacking well.