What 込 means
The verb around it sets the sense. In Japanese compounds ending in 込む, it can show movement inward, as in 押し込む (“force something in”), or an action carried on deeply, as in 話し込む (“talk at length”). Read the whole compound to choose the meaning.
込 is a Japanese-made kanji (kokuji), built from 入 (“enter”) and 辵, a movement element written 辶 on the left. Japanese dictionaries cite 込む meaning “put into” in the Japanese tale Utsuho Monogatari around 970–999, and “be crowded” in writer Murasaki Shikibu’s diary around 1010. These dates mark word uses, not the invention of the character.
For a crowded train or road, 混む is the clearer everyday spelling; 込む is also accepted.
Read the whole compound before translating 込 as “crowded.”
Don't confuse it with
1Combination ideas
3Questions people ask
1Why does 込 show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
How to type 込
込\8FBCCodes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.

