What were WW1 tracer bullets downsides?

Answer 1

Tracer bullets are still used today and any downsides would still apply today. I have a hard time seeing any unique disadvantages particular to those used in WW1.

Tracers are more expensive to manufacture.

Tracers are more hazardous to store due to the volatile chemicals they employ to create the glowing trails.

"Tracers work both ways" an old military proverb explained more in depth below.

Tracers lose energy more quickly than standard rounds. Kinetic energy is 1/2mv^2. All bullets lose energy as v decreases, but tracers also lose m, meaning both sides of the equation drop over distance. Though how much of a difference this makes is generally too small to really concern oneself with.

Tracers can cause fires because they use volatile chemicals, and a starting a fire may or may not be to your advantage.

It is important to understand that tracers have a very specific job they perform. Namely they create a visible trail that allows the operator of an automatic weapon to see (roughly) the path his bullets are taking. At long distances a gunner can "walk" his fire on the target by pivoting the gun until he sees his tracers going to the vicinity of those whom are the targets of his ill-will. Soldiers however have often quipped that "tracers work both ways". That is while it makes it easier for the gunner to see where his rounds are going, it also makes it easier for those being shot at to see where the rounds are coming from.