What does "high energy ahead" mean?

It indicates that there will be intensive screen content next.

For example, in the barrage video, Gao Nengjun will send a barrage reminder in advance before a horror clip or an amazing shot of a climax is about to be broadcast. If the energy is too high, you can also add "non-combatants evacuate quickly" to warn the audience;

In addition, there are hints such as "early warning of high energy ahead", "nuclear energy ahead", "low energy ahead" and "small high energy ahead", but there are also barrage hints of "false high energy ahead"

Source:

The earliest format was "high-energy reaction ahead, non-combatants quickly retreat", which was simplified to high-energy reaction ahead and finally evolved into a concise high-energy reaction ahead. There are variations such as nuclear energy ahead.

The high energy ahead comes from the Gundam series of mobile suit. Later, this line appeared in science fiction works such as Eva, Battlestar of Time and Space, and Battleship Yamato.