Is Qwen3.5-2B-Base or Qwen3.5-4B smaller?

Qwen3.5-2B-Base is smaller at Q4_K_M: 1.19 GiB against 2.52 GiB.

Which uses less memory at long context?

Qwen3.5-2B-Base — its KV cache at 32K context is 2.7x smaller, because of how its attention layers cache.

Model comparison

Qwen3.5-2B-Base vs Qwen3.5-4B

At Q4_K_M, Qwen3.5-2B-Base is the smaller download — 1,274,396,032 bytes against 2,707,513,696. At long context the gap widens: Qwen3.5-2B-Base's KV cache at 32K is 2.7× smaller, which usually matters more than the difference in weights.

From the file· summed bytes, KV per layer

Side by side

	Qwen3.5-2B-Base	Qwen3.5-4B
Parameters	2.3B	4.7B
Architecture	qwen35	qwen35
Layers	24	32
Native context	262,144	262,144
Mixture of experts	no	no
Quantizations published	8	57
Smallest quantization	1.15 GiB	1.42 GiB
Q4_K_M	1.19 GiB	2.52 GiB
Licence	apache-2.0	apache-2.0

KV cache by context

the term that decides long-context viability

Context	Qwen3.5-2B-Base	Qwen3.5-4B	Ratio
4,096	0.05 GiB	0.13 GiB	2.67×
8,192	0.09 GiB	0.25 GiB	2.67×
16,384	0.19 GiB	0.50 GiB	2.67×
32,768	0.38 GiB	1.00 GiB	2.67×
65,536	0.75 GiB	2.00 GiB	2.67×
131,072	1.50 GiB	4.00 GiB	2.67×