Channel saturation is the point where additional spend in a channel produces diminishing returns, because you have already reached most of the reachable audience. Costs rise and efficiency falls. It signals the need to expand into new channels rather than push harder on the current one.

A channel that worked brilliantly and then quietly got expensive has not broken. It has saturated. Pushing more budget into it is the most common and most expensive mistake, because rising CAC looks like a performance problem when it is actually a capacity limit. The signal to read is efficiency falling while spend rises.

Example:

A channel delivering steady CAC begins to require more spend for the same result. Nothing is wrong with the execution. You have simply reached most of the people it can reach.

How do you recognize channel saturation?

Acquisition cost rises steadily while spend increases and volume flattens. Efficiency declines even though execution has not changed.

What should you do when a channel saturates?

Expand into additional channels rather than pushing more budget into the saturated one, where the marginal return is now poor.