Here are some important features and ergonomics criteria:
Adjustability
Seat height: So your feet are flat on the floor, and knees are about 90°.
Seat depth: Good ergonomic chairs let you adjust how deep the seat is so your thighs are fully supported but the edge isn’t pressing behind your knees.
Armrests: Adjustable ones (height, width) are very useful.
Backrest tilt / recline: Helps you change posture during the day.
Lumbar Support
Base & Mobility
A 5-point base (5 wheels) gives good stability.

Casters (wheels) according to your floor type: hard vs carpet.
360° swivel helps you reach different parts of your desk without twisting.
Material
Mesh back: breathable, good for long hours, especially in warm climates.
Seat cushion: firm but comfortable foam or padding.
Build + Durability
Ergonomics Use