Is Disneyland crowded on Friday nights in winter?

Yes Disney is crowded everyday

some days more than others

and Fri -Sun its always crowded

Generally, Fridays to Sundays are crowded in Disneyland because most people have no engagements that day or the next day. It also depends on whether it's the holiday season or not. Generally, late September to mid-November is not busy, along with the first couple weeks of December. January generally isn't too busy either. However, any breaks celebrated during these times, like 3 day weekends will most likely be busy.

Hope you have fun at Disneyland!