GPT-5 vs GPT-5.1 Codex mini
Wins 5 of 7 areas
Coding · Reasoning · Images and charts · Long documents · Following instructions
Wins 1 of 7 areas
Agents
GPT-5 is the stronger all-rounder.GPT-5.1 Codex mini is cheaper and better at agents.
Scores updated · 18 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.
- ReasoningHard problems that need careful thinking30GPT-53 of 3 tests
- CodingWriting and fixing software10GPT-51 of 3 tests · 2 ties
- Images and chartsUnderstanding pictures, charts and video10GPT-51 of 1 test
- Long documentsFinding answers in very long texts10GPT-51 of 1 test
- Following instructionsDoing exactly what it is asked10GPT-51 of 1 test
- AgentsCarrying out multi-step tasks on its own01GPT-5.1 Codex mini1 of 1 test
- FactsGetting facts right instead of making them up11Even1 each
Agents, 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-5.1 Codex mini costs 80% 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 pulls ahead
- Answers hard knowledge questions correctlyAA-Omniscience · Accuracy+17.1points ahead
- Reasons across sets of long documentsAA-LCR+11.5points ahead
- Very hard expert questions across many subjectsHumanity's Last Exam+10points ahead
Where GPT-5.1 Codex mini pulls ahead
- Avoids making up answers it doesn't knowAA-Omniscience · Non-hallucination+30.6points ahead
- Real work tasks from 44 professionsGDPVal+6.7points ahead
Every test, side by side
All 18 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingGPT-5
- LMArena · WebDevGPT-5 by 175 rating points14181243+175 rating
- Terminal-Bench Hardtie32.633.3tie
- SciCodetie42.942.6tie
ReasoningGPT-5
- Humanity's Last ExamGPT-5 by 1028.518.5+10
- CritPtGPT-5 by 5.75.70+5.7
- GPQA DiamondGPT-5 by 4.185.481.3+4.1
FactsEven
- AA-Omniscience · Non-hallucinationGPT-5.1 Codex mini by 30.617.848.4+30.6
- AA-Omniscience · AccuracyGPT-5 by 17.140.323.2+17.1
Other results6 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.
- AIME 2025GPT-5 by 52.594.642.1+52.5
- τ²-Bench Telecom (AA run)GPT-5 by 21.984.862.9+21.9
- AA Agentic IndexGPT-5.1 Codex mini by 12.226.538.7+12.2
- AA-OmniscienceGPT-5 by 7.7-8.7-16.4+7.7
- AA IntelligenceGPT-5 by 2.62320.4+2.6
- Artificial Analysis Coding IndexGPT-5 by 1.437.836.4+1.4
Questions people ask
Which is better, GPT-5 or GPT-5.1 Codex mini?
GPT-5 wins five of the seven areas where both have results: coding, reasoning, images and charts, long documents and following instructions. GPT-5.1 Codex mini wins agents, and costs 80% less. They are level on facts.
Which is better for coding?
GPT-5. It wins 1 of the 3 coding tests both models report; GPT-5.1 Codex mini wins none, and 2 are ties.
Which is cheaper?
GPT-5 costs $1.25 per million input tokens and $10.00 per million output tokens; GPT-5.1 Codex mini costs $0.25 and $2.00. That makes GPT-5.1 Codex mini about 80% cheaper for the same work.
How do you compare the two?
We use the 18 benchmark tests both models have published scores on. The verdict counts the 12 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 6 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.