DeepSeek V4 Flash vs GPT-5.3-Codex
DeepSeek V4 Flash (2026) and GPT-5.3-Codex (2026) compare a standalone API model against a coding-specialized model. DeepSeek V4 Flash ships a 1m-token context window, while GPT-5.3-Codex ships a 400k-token context window. On SWE-bench Verified, GPT-5.3-Codex leads by 6 pts. On pricing, DeepSeek V4 Flash costs $0.10/1M input tokens versus $1.75/1M for the alternative. This page treats the result as workflow and deployment fit, not a universal model winner.
Treat this as a product-type comparison: DeepSeek V4 Flash is standalone API model, while GPT-5.3-Codex is coding-specialized model. Choose based on workflow fit before reading any benchmark or price row as decisive.
Decision scorecard
Local evidence first| Signal | DeepSeek V4 Flash | GPT-5.3-Codex |
|---|---|---|
| Product type | Standalone API model | Coding-specialized model |
| Best for | reasoning-heavy apps, tool-calling agents, and long-context analysis | custom coding agents, code generation, and tool loops |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1m | 400k |
| Cheapest output | $0.20/1M tokens | $14/1M tokens |
| Provider routes | 5 tracked | 3 tracked |
| Shared benchmarks | 3 rows | SWE-bench Verified leader |
Decision tradeoffs
- DeepSeek V4 Flash has the larger context window for long prompts, retrieval packs, or transcript analysis.
- DeepSeek V4 Flash has the lower cheapest tracked output price at $0.20/1M tokens.
- DeepSeek V4 Flash has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags DeepSeek V4 Flash for Coding, RAG, and Agents.
- GPT-5.3-Codex holds a shared-benchmark lead on SWE-bench Verified, ahead by 6 points.
- GPT-5.3-Codex uniquely exposes Vision, Code execution, and Computer use in local model data.
- Local decision data tags GPT-5.3-Codex for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
DeepSeek V4 Flash
$128
Cheapest tracked route/tier: OpenRouter
GPT-5.3-Codex
$4,900
Cheapest tracked route/tier: OpenRouter
Estimated monthly gap: $4,772. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
- GPT-5.3-Codex is $13.80/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- GPT-5.3-Codex adds Vision, Code execution, and Computer use in local capability data.
- Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
- DeepSeek V4 Flash is $13.80/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Vision, Code execution, and Computer use before moving production traffic.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-04-24 | 2026-02-05 |
| Context window | 1m | 400k |
| Parameters | 284B | — |
| Architecture | mixture of experts | decoder only |
| License | MIT(OSI) | Proprietary |
| Openness | Open source | Proprietary |
| Commercial use | Commercial use allowed | Commercial use with conditions |
| Knowledge cutoff | - | 2025-08 |
Pricing and availability
| Pricing attribute | DeepSeek V4 Flash | GPT-5.3-Codex |
|---|---|---|
| Input price | $0.10/1M tokens | $1.75/1M tokens |
| Output price | $0.20/1M tokens | $14/1M tokens |
| Providers |
Capabilities
| Capability | DeepSeek V4 Flash | GPT-5.3-Codex |
|---|---|---|
| Vision | No | Yes |
| Multimodal | No | No |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | No | Yes |
| IDE integration | No | No |
| Computer use | No | Yes |
| Parallel agents | No | No |
Benchmarks
| Benchmark | DeepSeek V4 Flash | GPT-5.3-Codex |
|---|---|---|
| SWE-bench Verified | 79.0 | 85.0 |
| SWE-bench Pro | 52.6 | 56.8 |
| Terminal-Bench 2.0 | 56.9 | 77.3 |
Deep dive
On shared benchmark coverage, SWE-bench Verified has DeepSeek V4 Flash at 79 and GPT-5.3-Codex at 85, with GPT-5.3-Codex ahead by 6 points; SWE-bench Pro has DeepSeek V4 Flash at 52.6 and GPT-5.3-Codex at 56.8, with GPT-5.3-Codex ahead by 4.2 points; Terminal-Bench 2.0 has DeepSeek V4 Flash at 56.9 and GPT-5.3-Codex at 77.3, with GPT-5.3-Codex ahead by 20.4 points. The largest visible gap is 20.4 points on Terminal-Bench 2.0, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint differs most on vision: GPT-5.3-Codex and code execution: GPT-5.3-Codex. Both models share reasoning mode, function calling, tool use, and structured outputs, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, DeepSeek V4 Flash lists $0.10/1M input and $0.20/1M output tokens on the cheapest tracked provider, while GPT-5.3-Codex lists $1.75/1M input and $14/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts DeepSeek V4 Flash lower by about $5.30 per million blended tokens. Availability is 5 providers versus 3, so concentration risk also matters.
Choose DeepSeek V4 Flash when long-context analysis, larger context windows, and lower input-token cost are central to the workload. Choose GPT-5.3-Codex when coding workflow support are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship.
FAQ
Which has a larger context window, DeepSeek V4 Flash or GPT-5.3-Codex?
DeepSeek V4 Flash supports 1m tokens, while GPT-5.3-Codex supports 400k tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Which is cheaper, DeepSeek V4 Flash or GPT-5.3-Codex?
DeepSeek V4 Flash is cheaper on tracked token pricing. DeepSeek V4 Flash costs $0.10/1M input and $0.20/1M output tokens. GPT-5.3-Codex costs $1.75/1M input and $14/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is DeepSeek V4 Flash or GPT-5.3-Codex open source?
DeepSeek V4 Flash is listed under MIT. GPT-5.3-Codex is listed under Proprietary. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for vision, DeepSeek V4 Flash or GPT-5.3-Codex?
GPT-5.3-Codex has the clearer documented vision signal in this comparison. If vision is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for reasoning mode, DeepSeek V4 Flash or GPT-5.3-Codex?
Both DeepSeek V4 Flash and GPT-5.3-Codex expose reasoning mode. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Where can I run DeepSeek V4 Flash and GPT-5.3-Codex?
DeepSeek V4 Flash is available on DeepSeek Platform, OpenRouter, Microsoft Foundry, Vercel AI Gateway, and Novita AI. GPT-5.3-Codex is available on OpenRouter, OpenAI API, and Vercel AI Gateway. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-06-10. Data sourced from public model cards and provider documentation.