Unlike a harami, which compares bodies, an inside bar compares full ranges. The previous bar is called the mother bar. Two or more inside bars in a row indicate strong compression.
The standard play is a breakout of the mother bar's range with a stop on the opposite side. Because the mother bar range is by definition larger than the inside bar, risk is defined and often modest relative to the move that follows a genuine expansion.
Realistically, many inside bar breakouts fail: contraction resolves in whichever direction, and both sides get run in choppy markets. Filters that help are requiring the inside bar to sit in the upper or lower third of the mother bar, requiring an existing trend, and skipping setups where the mother bar range is tiny relative to atr.
Related: outside-bar, harami, narrow-range-bar