DeepSeek V4 Flash vs GPT-OSS 120B — Price, Context, and Capability Compared
DeepSeek V4 Flash vs GPT-OSS 120B: which should I use?
GPT-OSS 120B costs 1.5× more per blended million tokens than DeepSeek V4 Flash. GPT-OSS 120B has the larger context window (131,072 tokens). Default to DeepSeek V4 Flash unless you specifically need GPT-OSS 120B's edge. Only GPT-OSS 120B exposes an extended-thinking mode.
Price, speed, and task evidence
Task verdict
Best-fit task signals from the published model strengths; this is not a substitute for a controlled benchmark.
| Fact | DeepSeek V4 Flash | GPT-OSS 120B |
|---|---|---|
| Best fit | High-volume coding and text workloads where budget is the top priority. | Self-hostable or Groq-speed agentic workflows on open weights. |
| Reasoning mode | Unavailable | Available |
Effective workload cost
Modeled for Coding Agent: 20,000 input + 2,000 output tokens per task, 1 turn. This is a workload model, not a provider quote.
| Fact | DeepSeek V4 Flash | GPT-OSS 120B |
|---|---|---|
| Coding Agent / task | $0.0034 (modeled) (winner) | $0.0042 (modeled) |
| Input / output rate | $0.14 / $0.28 per M | $0.15 / $0.60 per M |
Speed
Only non-estimated benchmark results are shown as measured.
| Fact | DeepSeek V4 Flash | GPT-OSS 120B |
|---|---|---|
| Measured throughput | 132 tokens/s | 780 tokens/s (winner) |
| Time to first token | 280 ms | 160 ms |
API compatibility
Provider-level wire-format and SDK facts; model-specific parameter differences may still apply.
| Fact | DeepSeek V4 Flash | GPT-OSS 120B |
|---|---|---|
| OpenAI SDK | Usable | Usable |
| Request shape | OpenAI-compatible chat/completions; set model to a deepseek-* id and point base_url at api.deepseek.com. | OpenAI-compatible chat/completions endpoint at api.groq.com/openai/v1. |
| Streaming | SSE (OpenAI delta) | SSE (OpenAI delta) |
Privacy and retention
Provider policy and residency facts from the verified provider registry. A missing retention policy is not treated as a guarantee.
| Fact | DeepSeek V4 Flash | GPT-OSS 120B |
|---|---|---|
| Provider says API data trains models | Unavailable | Unavailable |
| Published retention period | Unavailable | Unavailable |
| Data residency | Unavailable | US |
Migration effort
Direction is from each displayed model to the other. Effort is derived from provider compatibility and published parameter maps.
| Fact | DeepSeek V4 Flash | GPT-OSS 120B |
|---|---|---|
| Move DeepSeek V4 Flash → GPT-OSS 120B | config; 0 breaking parameter differences | Target: GPT-OSS 120B |
| Move GPT-OSS 120B → DeepSeek V4 Flash | Source: GPT-OSS 120B | config; 2 breaking parameter differences |
| Why | Keep the `openai` SDK; change `baseURL` and the API key. | Keep the `openai` SDK; change `baseURL` and the API key. |
Spec comparison
| DeepSeek V4 Flash | GPT-OSS 120B | |
|---|---|---|
| Price (input) | $0.14/M ✓ | $0.15/M |
| Price (output) | $0.28/M ✓ | $0.60/M |
| Blended price | $0.17/M ✓ | $0.26/M |
| Context window | 128,000 tokens | 131,072 tokens ✓ |
| Max output | 32,000 tokens | 32,768 tokens ✓ |
| Modalities | text | text |
| Reasoning mode | No | Yes |
| Released | 2026-05 | 2025-08 |
| Speed | 132 t/s | 780 t/s ✓ |
Cost at scale (3:1 blended)
| Tokens / month | DeepSeek V4 Flash | GPT-OSS 120B | Delta |
|---|---|---|---|
| 1,000,000 | $0.17 | $0.26 | $0.09 (1.5×) |
| 10,000,000 | $1.75 | $2.62 | $0.87 (1.5×) |
| 100,000,000 | $17.50 | $26.25 | $8.75 (1.5×) |
Choose DeepSeek V4 Flash if…
- ✓Latest DeepSeek flagship, non-thinking mode
- ✓Aggressively cheap per-token pricing
- ✓Strong algorithmic coding
- ✓High-volume coding and text workloads where budget is the top priority.
Choose GPT-OSS 120B if…
- ✓Open-weight MoE flagship
- ✓Ultra-fast on Groq LPUs
- ✓Strong agentic tool-use
- ✓Self-hostable or Groq-speed agentic workflows on open weights.
Run this exact matchup right now
Send the same prompt to DeepSeek V4 Flash and GPT-OSS 120B side by side and see the outputs yourself.
Try DeepSeek V4 Flash vs GPT-OSS 120B FreeFAQ
Is DeepSeek V4 Flash cheaper than GPT-OSS 120B?
DeepSeek V4 Flash is cheaper, at $0.17 per million blended tokens vs $0.26 for GPT-OSS 120B.
Which has the bigger context window, DeepSeek V4 Flash or GPT-OSS 120B?
GPT-OSS 120B has the larger context window: 131,072 tokens vs 128,000.
Can DeepSeek V4 Flash replace GPT-OSS 120B for coding?
Both are viable for coding. Latest DeepSeek flagship, non-thinking mode (DeepSeek V4 Flash) vs Open-weight MoE flagship (GPT-OSS 120B) — pick based on which strength matters more for your workload.
Which is faster, DeepSeek V4 Flash or GPT-OSS 120B?
GPT-OSS 120B is faster: 780 t/s vs 132 t/s, measured on our speed benchmarks.
Neither of these? See GPT-OSS 120B alternatives.
Related
Pricing verified 2026-04-06. Specs verified 2026-08-08.