Model comparison
GPT-5.3 Codex vs o3
Head-to-head evidence from 13 shared benchmark results across 6 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-5.3 Codex #26 (Supported); o3 #131 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5.3 Codex and o3 share 13 comparable benchmark results. 0 of 8 categories are comparable. 8 results are unique to GPT-5.3 Codex; 3 to o3.
Updated July 20, 2026- Shared results
- 13
- GPT-5.3 Codex only
- 8
- o3 only
- 3
- Comparable categories
- 0 / 8
Benchmark data for GPT-5.3 Codex and o3 is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 13 shared benchmark results across 6 evidence categories; 0 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
BenchLM has partial data for these models, but not enough overlapping benchmark coverage to produce a fair score-level comparison yet.
GPT-5.3 Codex is priced at $1.75 input / $14.00 output per 1M tokens, versus $2.00 input / $8.00 output per 1M tokens for o3. GPT-5.3 Codex has the larger context window at 400K, compared with 200K for o3.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
| Category | GPT-5.3 Codex | Δ | o3 |
|---|---|---|---|
| Agentic | GPT-5.3 Codex71.4 | MarginNo overlap | o3Not measured |
| Coding | GPT-5.3 Codex67.2 | MarginNo overlap | o3Not measured |
| Math | GPT-5.3 CodexNot measured | MarginNo overlap | o314.5 |
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-5.3 Codex | o3 | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.3 Codex$1.75 input / $14 output | o3$2 input / $8 output | o3 has the lower combined listed price. |
| Generation speedtokens per second | GPT-5.3 Codex79 tok/s | o3118 tok/s | o3 has the higher measured throughput. |
| First-answer latencyseconds to first token | GPT-5.3 Codex88.26 s | o35.38 s | o3 reaches the first token sooner. |
| Context windowmaximum listed tokens | GPT-5.3 Codex400K | o3200K | GPT-5.3 Codex lists the larger context window. |
Benchmark Deep Dive
Agentic5 benchmarks
Coding5 benchmarks
Reasoning2 benchmarks
Knowledge6 benchmarks
| Benchmark | GPT-5.3 Codex | o3 | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 44.3% | 30.4% | GPT-5.3 Codex leads |
| AA-GPQA DiamondSource | 91.5% | 82.7% | GPT-5.3 Codex leads |
| AA-HLESource | 39.9% | 20.0% | GPT-5.3 Codex leads |
| AA-Omniscience IndexSource | 9.9% | -15.3% | GPT-5.3 Codex leads |
| AA-Omniscience AccuracySource | 51.8% | 38.4% | GPT-5.3 Codex leads |
| AA-Omniscience Hallucination RateSource | 86.9% | 87.1% | GPT-5.3 Codex leads |
Math3 benchmarks
Multimodal2 benchmarks
Inst. Following1 benchmarks
| Benchmark | GPT-5.3 Codex | o3 | Result |
|---|---|---|---|
| AA-IFBenchSource | 75.4% | 71.4% | GPT-5.3 Codex leads |
Frequently Asked Questions (3)
Can I compare GPT-5.3 Codex and o3 on BenchLM yet?
Not fully yet. BenchLM is tracking both models, but the sourced benchmark breakdown for this comparison is still coming soon.
Why does this comparison show “coming soon”?
BenchLM only shows category winners and benchmark-level calls when we have sourced results that can be compared fairly. For these models, the public benchmark coverage is not complete enough yet.
What data is available for GPT-5.3 Codex and o3 today?
GPT-5.3 Codex: $1.75 input / $14.00 output per 1M tokens o3: $2.00 input / $8.00 output per 1M tokens Both model pages still include creator, context window, reasoning mode, and other metadata while benchmark coverage fills in.
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