Gemini 3.1 Flash-Lite vs GPT-5.3-Codex
Gemini 3.1 Flash-Lite (2026) and GPT-5.3-Codex (2026) are agentic coding models from Google DeepMind and OpenAI. Gemini 3.1 Flash-Lite ships a 1M-token context window, while GPT-5.3-Codex ships a 400K-token context window. On pricing, Gemini 3.1 Flash-Lite costs $0.25/1M input tokens versus $1.75/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit. It focuses on practical selection signals rather than broad model-family marketing.
Gemini 3.1 Flash-Lite is ~600% cheaper at $0.25/1M; pay for GPT-5.3-Codex only for coding workflow support.
Decision scorecard
Local evidence first| Signal | Gemini 3.1 Flash-Lite | GPT-5.3-Codex |
|---|---|---|
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1M | 400K |
| Cheapest output | $1.5/1M tokens | $14/1M tokens |
| Provider routes | 2 tracked | 2 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Gemini 3.1 Flash-Lite has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Gemini 3.1 Flash-Lite has the lower cheapest tracked output price at $1.5/1M tokens.
- Gemini 3.1 Flash-Lite uniquely exposes Multimodal in local model data.
- Local decision data tags Gemini 3.1 Flash-Lite for Coding, RAG, and Agents.
- GPT-5.3-Codex uniquely exposes Reasoning 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 prices on this page.
Gemini 3.1 Flash-Lite
$575
Cheapest tracked route: Google AI Studio
GPT-5.3-Codex
$4,900
Cheapest tracked route: OpenRouter
Estimated monthly gap: $4,325. Batch, cache, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- GPT-5.3-Codex is $12.50/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Check replacement coverage for Multimodal before moving production traffic.
- GPT-5.3-Codex adds Reasoning in local capability data.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Gemini 3.1 Flash-Lite is $12.50/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Reasoning before moving production traffic.
- Gemini 3.1 Flash-Lite adds Multimodal in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-05-07 | 2026-02-05 |
| Context window | 1M | 400K |
| Parameters | — | — |
| Architecture | decoder only | decoder only |
| License | Proprietary | Proprietary |
| Knowledge cutoff | 2025-01 | 2025-08 |
Pricing and availability
| Pricing attribute | Gemini 3.1 Flash-Lite | GPT-5.3-Codex |
|---|---|---|
| Input price | $0.25/1M tokens | $1.75/1M tokens |
| Output price | $1.5/1M tokens | $14/1M tokens |
| Providers |
Capabilities
| Capability | Gemini 3.1 Flash-Lite | GPT-5.3-Codex |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | No |
| Reasoning | No | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | Yes |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on multimodal input: Gemini 3.1 Flash-Lite and reasoning mode: GPT-5.3-Codex. Both models share vision, 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, Gemini 3.1 Flash-Lite lists $0.25/1M input and $1.5/1M output tokens, 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 Gemini 3.1 Flash-Lite lower by about $4.8 per million blended tokens. Availability is 2 providers versus 2, so concentration risk also matters.
Choose Gemini 3.1 Flash-Lite when coding workflow support, 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. This keeps the decision grounded in measurable tradeoffs instead of brand-level assumptions. It also helps separate model capability from provider packaging, which can change cost and latency.
FAQ
Which has a larger context window, Gemini 3.1 Flash-Lite or GPT-5.3-Codex?
Gemini 3.1 Flash-Lite 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, Gemini 3.1 Flash-Lite or GPT-5.3-Codex?
Gemini 3.1 Flash-Lite is cheaper on tracked token pricing. Gemini 3.1 Flash-Lite costs $0.25/1M input and $1.5/1M 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 Gemini 3.1 Flash-Lite or GPT-5.3-Codex open source?
Gemini 3.1 Flash-Lite is listed under Proprietary. 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, Gemini 3.1 Flash-Lite or GPT-5.3-Codex?
Both Gemini 3.1 Flash-Lite and GPT-5.3-Codex expose vision. 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.
Which is better for multimodal input, Gemini 3.1 Flash-Lite or GPT-5.3-Codex?
Gemini 3.1 Flash-Lite has the clearer documented multimodal input signal in this comparison. If multimodal input is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run Gemini 3.1 Flash-Lite and GPT-5.3-Codex?
Gemini 3.1 Flash-Lite is available on Google AI Studio and OpenRouter. GPT-5.3-Codex is available on OpenRouter and OpenAI API. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-05-11. Data sourced from public model cards and provider documentation.