Gemini 2.5 Flash vs Gemini 3 Flash Preview vs DeepSeek-V3.1
Gemini 3 Flash Preview comes out ahead, 73 to 68 and 55 on our weighted score, though DeepSeek-V3.1 is 47% cheaper per token.
GoogleGemini 2.5 Flash
68/100- ECI140.8
- Price$0.30 / $2.50
- Context1.05M
- Our pickGoogle
Gemini 3 Flash Preview
73/100- ECI151.8
- Price$0.50 / $3.00
- Context1.05M
DeepSeekDeepSeek-V3.1
55/100- ECI139.9
- Price$0.385 / $1.25
- Context131K
Gemini 3 Flash Preview is our pick
Gemini 3 Flash Preview is the better all-round choice, scoring 73/100 against Gemini 2.5 Flash (68) and DeepSeek-V3.1 (55). It leads on capability. DeepSeek-V3.1 wins on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityGemini 3 Flash PreviewCapabilities Index (ECI): Gemini 3 Flash Preview 151.8 · Gemini 2.5 Flash 140.8 · DeepSeek-V3.1 139.9
- Lowest priceDeepSeek-V3.1DeepSeek-V3.1 $0.601 · Gemini 2.5 Flash $0.85 · Gemini 3 Flash Preview $1.13 per 1M tokens (3:1 blend)
- Longest contextGemini 2.5 Flash and Gemini 3 Flash PreviewGemini 2.5 Flash 1,048,576 · Gemini 3 Flash Preview 1,048,576 · DeepSeek-V3.1 131,072 tokens
- Widest inputsGemini 2.5 Flash and Gemini 3 Flash PreviewGemini 2.5 Flash: Text, Images, PDFs, Audio, Video · Gemini 3 Flash Preview: Text, Images, PDFs, Audio, Video · DeepSeek-V3.1: Text
- Self-hostingDeepSeek-V3.1Publishes downloadable weights (MIT License)
| Measure | Weight | Gemini 2.5 Flash | Gemini 3 Flash Preview | DeepSeek-V3.1 |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 67 | 80 | 65 |
| Price | 25% | 53 | 47 | 60 |
| Inputs & features | 15% | 100 | 100 | 35 |
| Context window | 10% | 61 | 61 | 24 |
| Overall | 100% | 68/100 | 73/100 | 55/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Gemini 2.5 FlashGoogle | Gemini 3 Flash PreviewGoogle | DeepSeek-V3.1DeepSeek |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 140.8 | 151.8 (best) | 139.9 |
| ECI rank | #97 of 148 | #43 of 148 (best) | #100 of 148 |
| GPQA DiamondGraduate-level science questions | — | 89.4% | — |
| FrontierMath Tiers 1–3Research-level mathematics | — | 51.2% | — |
| OTIS Mock AIME 2024–2025Competition mathematics | — | 95.6% | — |
| SWE-bench VerifiedFixing real GitHub issues | — | 75.4% | — |
| SimpleQA VerifiedShort factual questions | — | 66.8% | — |
| Price per million tokens | |||
| Input | $0.30 (best) | $0.50 | $0.385 |
| Output | $2.50 | $3.00 | $1.25 (best) |
| Cached input | $0.03 (best) | $0.05 | — |
| Blended (3:1) | $0.85 | $1.13 | $0.601 (best) |
| Long-context rate | Same rate | Same rate | Same rate |
| Price source | Official Google API | Official Google API | Median of 8 providers |
| Limits | |||
| Context window | 1,048,576 tokens (best) | 1,048,576 tokens (best) | 131,072 tokens |
| Max output | 65,536 tokens (best) | 65,536 tokens (best) | 8,192 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | No |
| PDFs | Yes | Yes | No |
| Audio | Yes | Yes | No |
| Video | Yes | Yes | No |
| Reasoning | Yes | Yesminimal · low · medium · high | Yes |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | No |
| Availability | |||
| Weights | Proprietary | Proprietary | OpenMIT License |
| API model ID | gemini-2.5-flash | gemini-3-flash-preview | — |
| API providers | 22 (best) | 20 | 8 |
| Released | Jun 17, 2025 | Dec 17, 2025 | Aug 21, 2025 |
| Knowledge cutoff | Jan 2025 | Jan 2025 | — |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Gemini 2.5 Flash$8.00
- Gemini 3 Flash Preview$11.00
- DeepSeek-V3.1$6.35
Which should you choose?
Which is better: Gemini 2.5 Flash, Gemini 3 Flash Preview or DeepSeek-V3.1?
Gemini 3 Flash Preview is the better all-round choice, scoring 73/100 against Gemini 2.5 Flash (68) and DeepSeek-V3.1 (55). It leads on capability. DeepSeek-V3.1 wins on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, Gemini 2.5 Flash, Gemini 3 Flash Preview or DeepSeek-V3.1?
DeepSeek-V3.1 is cheaper at $0.385 input / $1.25 output per million tokens (median across 8 API providers). Gemini 2.5 Flash costs $0.30 input / $2.50 output per million tokens (official Google API price); Gemini 3 Flash Preview costs $0.50 input / $3.00 output per million tokens (official Google API price). At a typical mix of three input tokens to one output token, that is $0.601 per million tokens for DeepSeek-V3.1 versus $0.85 for Gemini 2.5 Flash (1.4× as much) and $1.13 for Gemini 3 Flash Preview (1.9× as much).
Which scores higher on benchmarks?
Gemini 3 Flash Preview scores higher on the Capabilities Index (ECI): Gemini 3 Flash Preview 151.8 (#43 of 148), Gemini 2.5 Flash 140.8 (#97 of 148) and DeepSeek-V3.1 139.9 (#100 of 148). Their confidence ranges do not overlap (150.4–153.7 vs 138.5–142.3), so the gap is a real one.
Which is better for coding?
There are no published SWE-bench Verified results for Gemini 2.5 Flash and DeepSeek-V3.1 yet, so there is no like-for-like coding score. On overall capability, Gemini 3 Flash Preview leads, which tends to carry over to coding, but test on your own codebase. All three support tool calling for agent workflows.
Which has the bigger context window?
Gemini 2.5 Flash and Gemini 3 Flash Preview have the largest context windows (1,048,576 and 1,048,576 tokens), against 131,072 for DeepSeek-V3.1. Maximum output per response: Gemini 2.5 Flash up to 65,536, Gemini 3 Flash Preview up to 65,536, DeepSeek-V3.1 up to 8,192 tokens.
Which can read images, PDFs, audio or video?
Gemini 2.5 Flash accepts text, images, PDFs, audio and video; Gemini 3 Flash Preview accepts text, images, PDFs, audio and video; DeepSeek-V3.1 accepts text. Gemini 2.5 Flash handles the widest range of inputs.
Are any of these open source?
DeepSeek-V3.1 publishes its weights (MIT License) and can be self-hosted; Gemini 2.5 Flash and Gemini 3 Flash Preview is proprietary.
Which is newer?
Gemini 3 Flash Preview is the newest, released Dec 17, 2025. DeepSeek-V3.1 came out Aug 21, 2025; Gemini 2.5 Flash came out Jun 17, 2025. Knowledge cutoff: Gemini 2.5 Flash Jan 2025, Gemini 3 Flash Preview Jan 2025.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.
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