DeepSeek V4 vs ChatGPT
DeepSeek V4 vs ChatGPT (GPT-5.6): which one to choose in 2026?
It's the most-searched comparison. DeepSeek V4 and ChatGPT (powered by GPT-5.6 since July 2026) play in the same league on reasoning, but two differences change everything: DeepSeek is open source (MIT license) and costs up to 34 times less than GPT-5.6 via the API. GPT-5.6 keeps the edge on multimodal and some science scores. Here's the honest comparison, backed by official numbers, to choose based on your real usage and budget.
Head to head
DeepSeek V4 vs ChatGPT on the criteria that matter
Two very high-level models, but opposite philosophies: open and cheap versus closed and premium.
Price: DeepSeek is massively cheaper
This is the most striking gap. Via the API, GPT-5.6 Sol costs $5 for input and $30 for output per million tokens. DeepSeek V4-Pro costs about $0.44 for input and $0.87 for output, roughly 34 times cheaper on output. And V4-Flash ($0.14 / $0.28) widens the gap even further. For the same work, the DeepSeek bill is in a different league.
Free tier: both have one, but not the same limits
ChatGPT offers limited free access, then pushes toward the Plus subscription to reach the best models. DeepSeek gives free access to V4-Flash in the browser and the app, with no mandatory subscription. If your priority is "powerful and free with no credit card," DeepSeek is more generous.
Open source: DeepSeek is open, GPT-5.6 is closed
DeepSeek V4 is released under the MIT license: you can download the weights, self-host, adapt it, and build it into a commercial product with no restriction. GPT-5.6 is fully closed: available only via the API and OpenAI products, with no access to the model. For sovereignty, self-hosting, and data control, this is a decisive point in DeepSeek's favor.
Code and reasoning: close level, different measures
DeepSeek V4-Pro reaches 80.6% on SWE-bench Verified, one of the best open-source scores for autonomous code. OpenAI, for its part, doesn't publish this benchmark for GPT-5.6 (it reports other measures), which makes a direct comparison impossible on that specific point. On scientific reasoning (GPQA Diamond), GPT-5.6 leads (94.6% versus 90.1%). Both are excellent; DeepSeek offers this level in open source and far cheaper.
Privacy and data: neither hosts in Europe
Important point for use in Europe. With the official DeepSeek app, data passes through China (regulators have opened an inquiry). With ChatGPT, it goes to the United States. Neither is a sovereign European solution. If confidentiality is critical, the real workaround on the DeepSeek side is self-hosting the open-source version; on the ChatGPT side, there's no equivalent.
The European alternative: where does Mistral (Le Chat) fit in?
Many European users are actually torn between three options: DeepSeek, ChatGPT, and Mistral's Le Chat. Mistral, a French company, emphasizes European hosting and data sovereignty, but its models have a shorter context (256K) and often lag on pure code. In short: Le Chat for European sovereignty, DeepSeek for the best power-to-price ratio in open source, ChatGPT for the most polished multimodal.
Context window: DeepSeek V4 holds a million tokens
DeepSeek V4 (Pro and Flash) handles up to a million tokens of context, enough to analyze an entire codebase or a very long document in one pass. GPT-5.6 also handles a very large context according to third-party evaluations. On this criterion, both are on par; DeepSeek's advantage is offering that context at a fraction of the price.
In short: which one to choose?
Choose DeepSeek V4 if you want an open-source model, very strong at code and reasoning, at an unbeatable price, with the option to self-host. Choose ChatGPT (GPT-5.6) if you need the most advanced multimodal (image, audio) and the OpenAI tool ecosystem, and budget isn't a constraint. For most text and code use cases, DeepSeek delivers 90% of the result at a few percent of the cost.
Quick verdict
When to choose DeepSeek V4 over ChatGPT
Two excellent models, two opposite economic logics.
Choose DeepSeek V4 when
- Budget matters: up to 34 times cheaper than GPT-5.6
- You want open source (MIT) and the ability to self-host
- You need strong code performance and a 1M-token context
- You want free and powerful access without a subscription
Choose ChatGPT (GPT-5.6) when
- Image and audio multimodal is central to your usage
- You're already invested in the OpenAI ecosystem
- Certain high-end science benchmarks are a priority
- Cost per token isn't a constraint
Benchmarks
DeepSeek V4 vs GPT-5.6: the official numbers
A comparison based only on official data. Where OpenAI doesn't publish a benchmark for GPT-5.6, it's noted: we don't make up numbers.
OpenAI made a communication choice: GPT-5.6 (released July 9, 2026) isn't systematically evaluated on classic benchmarks like SWE-bench Verified, AIME, or MMLU, which it considers saturated. Comparing DeepSeek V4 and GPT-5.6 case by case therefore calls for caution: we only put head to head what's officially published, and leave the rest blank (Not published). What remains indisputable and verifiable is the price gap and the open-source status, two structural differences in DeepSeek's favor.
Output price: DeepSeek V4-Pro $0.87 vs GPT-5.6 Sol $30 per million tokens (about 34x)
Open source: DeepSeek V4 under MIT license, GPT-5.6 fully closed
Code: DeepSeek V4-Pro 80.6% SWE-bench Verified, GPT-5.6 not published on this test
Science: GPT-5.6 leads on GPQA Diamond (94.6% vs 90.1%)
Context: DeepSeek V4 handles 1M tokens
Free: V4-Flash accessible without a subscription in the browser
Comparison on official data
DeepSeek V4 vs GPT-5.6 Sol
A head-to-head limited to the numbers published by each vendor.
| Benchmark | V4-Pro Max Open source MIT DeepSeek | V4-Flash Fast and free DeepSeek | GPT-5.6 Sol Closed OpenAI |
|---|---|---|---|
SWE-bench Verified Autonomous code editing | 80.6% | 79.0% | Not published |
GPQA Diamond Scientific reasoning | 90.1% | 88.1% | 94.6% |
Terminal-Bench Terminal operations methodologies not identical | 67.9% | 56.9% | 91.9% |
SWE-bench Pro Code, extended variant | Not published | - | 64.6% |
Context window Maximum tokens | 1M | 1M | 1M |
Input price Per million tokens | ~$0.44 | $0.14 | $5 |
Output price Per million tokens | ~$0.87 | $0.28 | $30 |
License Model openness | MIT (open) | MIT (open) | Closed |
Multimodal Image and audio | Text and code | Text and code | Image, audio |
Sources: official DeepSeek model cards (April 2026, updated pricing) and OpenAI (GPT-5.6, July 2026). "Not published" means the vendor doesn't report that score, not that it's poor. Some tests use different methodologies and aren't directly comparable.
Price and openness
The same level, at a fraction of the price, and open source
The real difference between DeepSeek V4 and ChatGPT isn't raw quality, where both are excellent, but the business model. GPT-5.6 is a closed, premium service. DeepSeek V4 is an open model you can use free online, call by API for next to nothing, or host yourself. For a team watching its costs or wanting to keep control of its infrastructure, it's a step change.
- API output: $0.87 (V4-Pro) vs $30 (GPT-5.6 Sol) per million tokens
- V4-Flash free in the browser, no subscription
- Open weights under MIT license, self-hosting possible
- Free commercial use, no cap or restriction
Code and long context
A million tokens to reason over entire projects
DeepSeek V4 processes up to a million tokens in a single pass, so you can hand it a complete codebase, a long legal file, or several documents to analyze together. Combined with its 80.6% score on SWE-bench Verified, that makes it an excellent choice for assisted development and large-scale document analysis, where the cost of a premium model would quickly become prohibitive.
- 80.6% on SWE-bench Verified (autonomous code editing)
- 1M-token context for large projects and documents
- Two modes: direct answer or deep thinking
- Ideal for development on a controlled budget
Related pages
Continue the comparison
DeepSeek against the other major models, and the details of each version.
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The best way to compare is to try it on your real tasks
Open the chat and run DeepSeek V4 on a coding problem, a translation, or a long document. Free, no install, no credit card. You'll immediately see whether you need to pay for a premium model, or whether DeepSeek already does the job.