GPT-5.3 Codex vs GPT-5.5
Wins 0 of 7 areas
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Wins 5 of 7 areas
Coding · Reasoning · Facts · Images and charts · Long documents
GPT-5.5 is the stronger all-rounder.GPT-5.3 Codex is cheaper.
Scores updated · 22 tests both models report · How we compare
Where each one wins
Tests won in each of the seven areas where both have results. Each piece is one test, so a longer bar means more evidence; grey means the two scored within a point of each other.
- CodingWriting and fixing software04GPT-5.54 of 4 tests
- ReasoningHard problems that need careful thinking03GPT-5.53 of 3 tests
- FactsGetting facts right instead of making them up01GPT-5.51 of 2 tests · 1 tie
- Images and chartsUnderstanding pictures, charts and video01GPT-5.51 of 1 test
- Long documentsFinding answers in very long texts01GPT-5.51 of 1 test
- AgentsCarrying out multi-step tasks on its own11Even1 each
- Following instructionsDoing exactly what it is asked00Even0 each · 1 tie
Images and charts, long documents and following instructions rest on a single test each.
What it costs
Prices per million tokens, roughly 750,000 words. The bars show the cost of a million tokens read plus a million written.
GPT-5.3 Codex costs 55% less for the same work.
The biggest differences
The tests each model wins by the widest margin, up to three each. Scores are out of 100.
Where GPT-5.5 pulls ahead
- Completes tasks by operating a computer desktopOSWorld-Verified+14points ahead
- Research-level physics problemsCritPt+10.2points ahead
- Hard command-line tasks in a real terminalTerminal-Bench Hard+7.6points ahead
Where GPT-5.3 Codex pulls ahead
- Real work tasks from 44 professionsGDPVal+6.3points ahead
Every test, side by side
All 22 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingGPT-5.5
- LMArena · WebDevGPT-5.5 by 104 rating points14081512+104 rating
- Terminal-Bench HardGPT-5.5 by 7.65360.6+7.6
- SciCodeGPT-5.5 by 2.653.255.8+2.6
- SWE-bench ProGPT-5.5 by 1.856.858.6+1.8
AgentsEven
- OSWorld-VerifiedGPT-5.5 by 1464.778.7+14
- GDPValGPT-5.3 Codex by 6.34942.7+6.3
ReasoningGPT-5.5
- CritPtGPT-5.5 by 10.216.927.1+10.2
- Humanity's Last ExamGPT-5.5 by 3.342.545.8+3.3
- GPQA DiamondGPT-5.5 by 291.593.5+2
FactsGPT-5.5
- AA-Omniscience · AccuracyGPT-5.5 by 5.152.958+5.1
- AA-Omniscience · Non-hallucinationtie10.811tie
Other results8 tests, not counted
Tests outside the eight areas. They are not counted above: several are summary scores built from other tests, or the same test under another name.
- HiL-Bench (Tools-allowed)GPT-5.5 by 35.44.339.7+35.4
- AA Agentic IndexGPT-5.3 Codex by 23.260.537.3+23.2
- Artificial Analysis Coding IndexGPT-5.5 by 21.853.174.9+21.8
- AA-OmniscienceGPT-5.5 by 9.610.920.5+9.6
- LiveBenchGPT-5.5 by 7.972.880.7+7.9
- τ²-Bench Telecom (AA run)GPT-5.5 by 7.98693.9+7.9
- AA IntelligenceGPT-5.5 by 5.932.538.4+5.9
- Terminal-Bench 2.0GPT-5.5 by 5.477.382.7+5.4
Questions people ask
Which is better, GPT-5.3 Codex or GPT-5.5?
GPT-5.5 wins five of the seven areas where both have results: coding, reasoning, facts, images and charts and long documents. GPT-5.3 Codex wins none, but costs 55% less. They are level on agents and following instructions.
Which is better for coding?
GPT-5.5. It wins 4 of the 4 coding tests both models report; GPT-5.3 Codex wins none.
Which is cheaper?
GPT-5.3 Codex costs $1.75 per million input tokens and $14.00 per million output tokens; GPT-5.5 costs $5.00 and $30.00. That makes GPT-5.3 Codex about 55% cheaper for the same work.
How do you compare the two?
We use the 22 benchmark tests both models have published scores on. The verdict counts the 14 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 8 are listed but not counted, because several are summary scores or repeat a test. Each score is the one shown on the model's own page.