Both are OpenAI models. GPT-5.4 Mini is the newer, generally stronger default; reach for GPT-5.3-Codex when its lower price or specific profile matters more than the latest capabilities.
GPT-5.3-Codex and GPT-5.4 Mini are both OpenAI models, so the real question is not which lab to trust but which tier fits your workload and budget. GPT-5.3-Codex is openAI's coding-specialized agent model for autonomous software engineering. GPT-5.4 Mini is openAI's free, fast workhorse — capable general AI with no subscription needed. Since both come from the same lab, the comparison below focuses on the tier-and-cost trade-offs that actually separate them.
Key differences
Price: GPT-5.4 Mini is about 6× cheaper on input ($0.25/$2 per 1M tokens vs $1.5/$10 per 1M tokens) — a large enough gap that at scale it can be the single biggest line item in the decision.
Context window: GPT-5.4 Mini holds 3.1× more — 400K (~600 pages) vs 128K (~192 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-5.4 Mini is the newer model by about 31 days (released March 18, 2026), usually meaning fresher training data and capabilities.
Specifications
Spec
GPT-5.3-Codex
GPT-5.4 Mini
Provider
OpenAI (US)
OpenAI (US)
Released
2026
March 18, 2026
Context window
128K (~192 pages)
400K (~600 pages)
Price (in/out)
$1.5/$10 per 1M tokens
$0.25/$2 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, code
text, image, code
SWE-Bench Verified
Not published
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Dedicated coding agent: GPT-5.3-Codex — A core design strength of GPT-5.3-Codex.
CLI and IDE integration: GPT-5.3-Codex — A core design strength of GPT-5.3-Codex.
Autonomous software tasks: GPT-5.3-Codex — A core design strength of GPT-5.3-Codex.
Free for every ChatGPT user: GPT-5.4 Mini — A core design strength of GPT-5.4 Mini.
Fast, low-cost general tasks: GPT-5.4 Mini — A core design strength of GPT-5.4 Mini.
Subagent capabilities: GPT-5.4 Mini — A core design strength of GPT-5.4 Mini.
Lowest cost at scale: GPT-5.4 Mini — At $0.25/$2 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input: GPT-5.4 Mini — Its 400K window is about 3.1× larger, fitting roughly 600 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume: GPT-5.4 Mini — At $0.25/$2 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: GPT-5.4 Mini — Larger 400K window fits more in one prompt.
Anyone whose priority is dedicated coding agent: GPT-5.3-Codex — It is specifically built for that.
Anyone whose priority is free for every chatgpt user: GPT-5.4 Mini — That is its strongest area.
GPT-5.3-Codex: where it fits
OpenAI's coding-specialized agent model for autonomous software engineering. Released 2026 by OpenAI, it is built for dedicated coding agent, cLI and IDE integration, autonomous software tasks, and tool calling.
Its trade-offs are real: coding-specialized, narrower general use, and retired in favor of GPT-5.5 Codex. At $1.5 in / $10 out per million tokens, it sits in the mid price band.
GPT-5.4 Mini: where it fits
OpenAI's free, fast workhorse — capable general AI with no subscription needed. Released March 18, 2026 by OpenAI, it is built for free for every ChatGPT user, fast, low-cost general tasks, subagent capabilities, and native multimodal reasoning.
Its trade-offs: smaller context than flagship models, and not for the hardest reasoning. At $0.25 in / $2 out per million tokens, it sits in the budget price band.
The bottom line for this matchup
Because GPT-5.3-Codex and GPT-5.4 Mini come from the same lab (OpenAI), they share the same training philosophy and ecosystem — the decision is purely tier vs. cost. GPT-5.4 Mini is the more capable, more recent option; the other earns its place only when its price or latency profile fits a specific job better. Most teams should default to GPT-5.4 Mini and drop down only with a concrete reason.
Frequently asked questions
Is GPT-5.3-Codex or GPT-5.4 Mini 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, GPT-5.3-Codex leans toward dedicated coding agent while GPT-5.4 Mini leans toward free for every chatgpt user, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, GPT-5.3-Codex or GPT-5.4 Mini?
GPT-5.4 Mini is cheaper — $1.5/$10 per 1M tokens vs $0.25/$2 per 1M tokens, roughly 6× apart on input.
Which has the bigger context window?
GPT-5.4 Mini — 400K vs 128K, about 3.1× larger. Useful only if the model actually reasons over the full window, which not all do.
Should I upgrade from GPT-5.3-Codex to GPT-5.4 Mini?
Since both are OpenAI models, the newer one (GPT-5.4 Mini) is usually the better default unless you need a specific cost or latency profile from the other.
Which is newer, GPT-5.3-Codex or GPT-5.4 Mini?
GPT-5.4 Mini — released March 18, 2026, about 31 days after GPT-5.3-Codex.
GPT-5.3-Codex vs GPT-5.4 Mini
OpenAI · US | OpenAI · US · Updated June 2026
Quick verdict
Both are OpenAI models. GPT-5.4 Mini is the newer, generally stronger default; reach for GPT-5.3-Codex when its lower price or specific profile matters more than the latest capabilities.
GPT-5.3-Codex and GPT-5.4 Mini are both OpenAI models, so the real question is not which lab to trust but which tier fits your workload and budget. GPT-5.3-Codex is openAI's coding-specialized agent model for autonomous software engineering. GPT-5.4 Mini is openAI's free, fast workhorse — capable general AI with no subscription needed. Since both come from the same lab, the comparison below focuses on the tier-and-cost trade-offs that actually separate them.
Key differences at a glance
▸Price: GPT-5.4 Mini is about 6× cheaper on input ($0.25/$2 per 1M tokens vs $1.5/$10 per 1M tokens) — a large enough gap that at scale it can be the single biggest line item in the decision.
▸Context window: GPT-5.4 Mini holds 3.1× more — 400K (~600 pages) vs 128K (~192 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-5.4 Mini is the newer model by about 31 days (released March 18, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
Spec
GPT-5.3-Codex
GPT-5.4 Mini
Provider
OpenAI (US)
OpenAI (US)
Released
2026
March 18, 2026
Context window
128K (~192 pages)
400K (~600 pages)
Price (in/out)
$1.5/$10 per 1M tokens
$0.25/$2 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, code
text, image, code
SWE-Bench Verified
Not published
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Dedicated coding agent
GPT-5.3-Codex
A core design strength of GPT-5.3-Codex.
CLI and IDE integration
GPT-5.3-Codex
A core design strength of GPT-5.3-Codex.
Autonomous software tasks
GPT-5.3-Codex
A core design strength of GPT-5.3-Codex.
Free for every ChatGPT user
GPT-5.4 Mini
A core design strength of GPT-5.4 Mini.
Fast, low-cost general tasks
GPT-5.4 Mini
A core design strength of GPT-5.4 Mini.
Subagent capabilities
GPT-5.4 Mini
A core design strength of GPT-5.4 Mini.
Lowest cost at scale
GPT-5.4 Mini
At $0.25/$2 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input
GPT-5.4 Mini
Its 400K window is about 3.1× larger, fitting roughly 600 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume
→ GPT-5.4 Mini
At $0.25/$2 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
→ GPT-5.4 Mini
Larger 400K window fits more in one prompt.
Anyone whose priority is dedicated coding agent
→ GPT-5.3-Codex
It is specifically built for that.
Anyone whose priority is free for every chatgpt user
→ GPT-5.4 Mini
That is its strongest area.
GPT-5.3-Codex: where it fits
OpenAI's coding-specialized agent model for autonomous software engineering. Released 2026 by OpenAI, it is built for dedicated coding agent, cLI and IDE integration, autonomous software tasks, and tool calling.
Its trade-offs are real: coding-specialized, narrower general use, and retired in favor of GPT-5.5 Codex. At $1.5 in / $10 out per million tokens, it sits in the mid price band.
GPT-5.4 Mini: where it fits
OpenAI's free, fast workhorse — capable general AI with no subscription needed. Released March 18, 2026 by OpenAI, it is built for free for every ChatGPT user, fast, low-cost general tasks, subagent capabilities, and native multimodal reasoning.
Its trade-offs: smaller context than flagship models, and not for the hardest reasoning. At $0.25 in / $2 out per million tokens, it sits in the budget price band.
The bottom line for this matchup
Because GPT-5.3-Codex and GPT-5.4 Mini come from the same lab (OpenAI), they share the same training philosophy and ecosystem — the decision is purely tier vs. cost. GPT-5.4 Mini is the more capable, more recent option; the other earns its place only when its price or latency profile fits a specific job better. Most teams should default to GPT-5.4 Mini and drop down only with a concrete reason.
Want both GPT-5.3-Codex and GPT-5.4 Mini 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 GPT-5.3-Codex or GPT-5.4 Mini 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, GPT-5.3-Codex leans toward dedicated coding agent while GPT-5.4 Mini leans toward free for every chatgpt user, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, GPT-5.3-Codex or GPT-5.4 Mini?
GPT-5.4 Mini is cheaper — $1.5/$10 per 1M tokens vs $0.25/$2 per 1M tokens, roughly 6× apart on input.
Which has the bigger context window?
GPT-5.4 Mini — 400K vs 128K, about 3.1× larger. Useful only if the model actually reasons over the full window, which not all do.
Should I upgrade from GPT-5.3-Codex to GPT-5.4 Mini?
Since both are OpenAI models, the newer one (GPT-5.4 Mini) is usually the better default unless you need a specific cost or latency profile from the other.
Which is newer, GPT-5.3-Codex or GPT-5.4 Mini?
GPT-5.4 Mini — released March 18, 2026, about 31 days after GPT-5.3-Codex.
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.