Pick Gemini 2.5 Pro for 1m context via api or strong multimodal reasoning. Pick GPT-5.3-Codex for dedicated coding agent or cli and ide integration. On a tight budget at scale, Gemini 2.5 Pro is the value pick.
Gemini 2.5 Pro (Google) and GPT-5.3-Codex (OpenAI) are two of the models people most often weigh against each other in 2026. Gemini 2.5 Pro is google's previous-gen 2M flagship — still a strong long-context multimodal option. GPT-5.3-Codex is openAI's coding-specialized agent model for autonomous software engineering. They diverge most on price and context window — each quantified below from the models' real specs.
Key differences
Price: Gemini 2.5 Pro is about 1.4× cheaper on input ($1.25/$10 per 1M tokens vs $1.75/$14 per 1M tokens) — modest, but it adds up at steady volume.
Context window: Gemini 2.5 Pro holds 2.5× more — 1M (~1,500 pages) vs 400K (~600 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
Recency: GPT-5.3-Codex is the newer model by about 9 months (released February 24, 2026), usually meaning fresher training data and capabilities.
Specifications
Spec
Gemini 2.5 Pro
GPT-5.3-Codex
Provider
Google (US)
OpenAI (US)
Released
June 2025
February 24, 2026
Context window
1M (~1,500 pages)
400K (~600 pages)
Price (in/out)
$1.25/$10 per 1M tokens
$1.75/$14 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, audio, video, code
text, code
SWE-Bench Verified
Not published
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
1M context via API: Gemini 2.5 Pro — Its 1M window holds about 2.5× more than GPT-5.3-Codex's 400K in a single prompt.
Strong multimodal reasoning: Gemini 2.5 Pro — Google's previous-gen 2M flagship — still a strong long-context multimodal option — and it runs cheaper at $1.25/$10 per 1M tokens.
Science and maths benchmarks: Gemini 2.5 Pro — Google's previous-gen 2M flagship — still a strong long-context multimodal option — and it carries the larger 1M context.
Dedicated coding agent: GPT-5.3-Codex — OpenAI's coding-specialized agent model for autonomous software engineering — and it is the newer of the two.
CLI and IDE integration: GPT-5.3-Codex — GPT-5.3-Codex lists cLI and IDE integration among its strengths; Gemini 2.5 Pro does not.
Autonomous software tasks: GPT-5.3-Codex — GPT-5.3-Codex lists autonomous software tasks among its strengths; Gemini 2.5 Pro does not.
Lowest cost at scale: Gemini 2.5 Pro — At $1.25/$10 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input: Gemini 2.5 Pro — Its 1M window is about 2.5× larger than GPT-5.3-Codex's 400K, fitting roughly 1,500 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume: Gemini 2.5 Pro — At $1.25/$10 per 1M tokens it undercuts GPT-5.3-Codex, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases: Gemini 2.5 Pro — Larger 1M window fits more in one prompt.
Anyone whose priority is 1m context via api: Gemini 2.5 Pro — It is specifically built for that.
Anyone whose priority is dedicated coding agent: GPT-5.3-Codex — That is its strongest area.
Gemini 2.5 Pro: where it fits
Google's previous-gen 2M flagship — still a strong long-context multimodal option. Released June 2025 by Google, it is built for 1M context via API, strong multimodal reasoning, science and maths benchmarks, and whole-book and video analysis.
Its trade-offs are real: superseded by 3.x for newest features, and recall degrades on very long inputs. At $1.25 in / $10 out per million tokens, it sits in the mid price band.
GPT-5.3-Codex: where it fits
OpenAI's coding-specialized agent model for autonomous software engineering. Released February 24, 2026 by OpenAI, it is built for dedicated coding agent, cLI and IDE integration, autonomous software tasks, and tool calling.
Its trade-offs: coding-specialized, narrower general use, and retired in favor of GPT-5.5 Codex. At $1.75 in / $14 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
Gemini 2.5 Pro and GPT-5.3-Codex overlap enough that the right pick depends on your specific job. Gemini 2.5 Pro costs less per token; Gemini 2.5 Pro holds the larger context; and each leads in its own area — Gemini 2.5 Pro for 1m context via api, GPT-5.3-Codex for dedicated coding agent. Rather than crowning one, run the same hard task through both once and let the results decide.
Frequently asked questions
Is Gemini 2.5 Pro or GPT-5.3-Codex better for coding?
Public SWE-Bench figures are not available for either model, so the honest test is your own repository — run an identical real bug through both. By design, Gemini 2.5 Pro leans toward 1m context via api while GPT-5.3-Codex leans toward dedicated coding agent, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Gemini 2.5 Pro or GPT-5.3-Codex?
Gemini 2.5 Pro is cheaper — $1.25/$10 per 1M tokens vs $1.75/$14 per 1M tokens, roughly 1.4× apart on input.
Which has the bigger context window?
Gemini 2.5 Pro — 1M vs 400K, about 2.5× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both Gemini 2.5 Pro and GPT-5.3-Codex together?
Yes — a multi-model platform like LumiChats gives you Gemini 2.5 Pro, GPT-5.3-Codex and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, Gemini 2.5 Pro or GPT-5.3-Codex?
GPT-5.3-Codex — released February 24, 2026, about 9 months after Gemini 2.5 Pro.
Gemini 2.5 Pro vs GPT-5.3-Codex
Google · US | OpenAI · US · Updated June 2026
Quick verdict
Pick Gemini 2.5 Pro for 1m context via api or strong multimodal reasoning. Pick GPT-5.3-Codex for dedicated coding agent or cli and ide integration. On a tight budget at scale, Gemini 2.5 Pro is the value pick.
Gemini 2.5 Pro (Google) and GPT-5.3-Codex (OpenAI) are two of the models people most often weigh against each other in 2026. Gemini 2.5 Pro is google's previous-gen 2M flagship — still a strong long-context multimodal option. GPT-5.3-Codex is openAI's coding-specialized agent model for autonomous software engineering. They diverge most on price and context window — each quantified below from the models' real specs.
Key differences at a glance
▸Price: Gemini 2.5 Pro is about 1.4× cheaper on input ($1.25/$10 per 1M tokens vs $1.75/$14 per 1M tokens) — modest, but it adds up at steady volume.
▸Context window: Gemini 2.5 Pro holds 2.5× more — 1M (~1,500 pages) vs 400K (~600 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
▸Recency: GPT-5.3-Codex is the newer model by about 9 months (released February 24, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
Spec
Gemini 2.5 Pro
GPT-5.3-Codex
Provider
Google (US)
OpenAI (US)
Released
June 2025
February 24, 2026
Context window
1M (~1,500 pages)
400K (~600 pages)
Price (in/out)
$1.25/$10 per 1M tokens
$1.75/$14 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, audio, video, code
text, code
SWE-Bench Verified
Not published
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
1M context via API
Gemini 2.5 Pro
Its 1M window holds about 2.5× more than GPT-5.3-Codex's 400K in a single prompt.
Strong multimodal reasoning
Gemini 2.5 Pro
Google's previous-gen 2M flagship — still a strong long-context multimodal option — and it runs cheaper at $1.25/$10 per 1M tokens.
Science and maths benchmarks
Gemini 2.5 Pro
Google's previous-gen 2M flagship — still a strong long-context multimodal option — and it carries the larger 1M context.
Dedicated coding agent
GPT-5.3-Codex
OpenAI's coding-specialized agent model for autonomous software engineering — and it is the newer of the two.
CLI and IDE integration
GPT-5.3-Codex
GPT-5.3-Codex lists cLI and IDE integration among its strengths; Gemini 2.5 Pro does not.
Autonomous software tasks
GPT-5.3-Codex
GPT-5.3-Codex lists autonomous software tasks among its strengths; Gemini 2.5 Pro does not.
Lowest cost at scale
Gemini 2.5 Pro
At $1.25/$10 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input
Gemini 2.5 Pro
Its 1M window is about 2.5× larger than GPT-5.3-Codex's 400K, fitting roughly 1,500 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume
→ Gemini 2.5 Pro
At $1.25/$10 per 1M tokens it undercuts GPT-5.3-Codex, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases
→ Gemini 2.5 Pro
Larger 1M window fits more in one prompt.
Anyone whose priority is 1m context via api
→ Gemini 2.5 Pro
It is specifically built for that.
Anyone whose priority is dedicated coding agent
→ GPT-5.3-Codex
That is its strongest area.
Gemini 2.5 Pro: where it fits
Google's previous-gen 2M flagship — still a strong long-context multimodal option. Released June 2025 by Google, it is built for 1M context via API, strong multimodal reasoning, science and maths benchmarks, and whole-book and video analysis.
Its trade-offs are real: superseded by 3.x for newest features, and recall degrades on very long inputs. At $1.25 in / $10 out per million tokens, it sits in the mid price band.
GPT-5.3-Codex: where it fits
OpenAI's coding-specialized agent model for autonomous software engineering. Released February 24, 2026 by OpenAI, it is built for dedicated coding agent, cLI and IDE integration, autonomous software tasks, and tool calling.
Its trade-offs: coding-specialized, narrower general use, and retired in favor of GPT-5.5 Codex. At $1.75 in / $14 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
Gemini 2.5 Pro and GPT-5.3-Codex overlap enough that the right pick depends on your specific job. Gemini 2.5 Pro costs less per token; Gemini 2.5 Pro holds the larger context; and each leads in its own area — Gemini 2.5 Pro for 1m context via api, GPT-5.3-Codex for dedicated coding agent. Rather than crowning one, run the same hard task through both once and let the results decide.
Want both Gemini 2.5 Pro and GPT-5.3-Codex without two subscriptions? LumiChats gives you these plus 40+ models under one ₹69/day pass (about $1/day) — draft with one, cross-check with the other.
Is Gemini 2.5 Pro or GPT-5.3-Codex better for coding?
Public SWE-Bench figures are not available for either model, so the honest test is your own repository — run an identical real bug through both. By design, Gemini 2.5 Pro leans toward 1m context via api while GPT-5.3-Codex leans toward dedicated coding agent, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Gemini 2.5 Pro or GPT-5.3-Codex?
Gemini 2.5 Pro is cheaper — $1.25/$10 per 1M tokens vs $1.75/$14 per 1M tokens, roughly 1.4× apart on input.
Which has the bigger context window?
Gemini 2.5 Pro — 1M vs 400K, about 2.5× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both Gemini 2.5 Pro and GPT-5.3-Codex together?
Yes — a multi-model platform like LumiChats gives you Gemini 2.5 Pro, GPT-5.3-Codex and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, Gemini 2.5 Pro or GPT-5.3-Codex?
GPT-5.3-Codex — released February 24, 2026, about 9 months after Gemini 2.5 Pro.
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.