GPT-5.3-Codex vs GPT-5.5 for humanising AI text
GPT-5.3-Codex wins, 97–94
Same 12 humanising AI text tasks, marked blind by three rival labs. GPT-5.3-Codex took 3 tasks, GPT-5.5 took 0, 9 tied. Tested 16 Aug 2026.
Where they differed most
Rewrite this so it sounds like a person wrote it, keeping every fact — the invoice number, the amount, the due date, the attachment: 'I hope this email finds you well. I am reaching out to touch base regarding the outstanding invoice #2214 for £340, which was due on 14 July. Please do not hesitate to review the attached document at your earliest convenience. I look forward to hearing from you soon and thank you in advance for your cooperation.' Same politeness, human voice, probably shorter.
Hi [Name], I hope you’re well. Just a quick follow-up on invoice **#2214** for **£340**, which was due on **14 July**. I’ve attached it here for your review when you have a moment. Thanks in advance, and I look forward to hearing from you. Best, [Your Name]
Hi, just following up on the outstanding invoice #2214 for £340, which was due on 14 July. I’ve attached the document for your reference. Thanks in advance, and I look forward to hearing from you.
Task by task
| Task | GPT-5.3-Codex | GPT-5.5 |
|---|---|---|
| The touching-base email | 10 | 9 |
| De-guru the bio | 10 | 9 |
| Product page, human voice | 10 | 10 |
| Strip the tics | 9 | 9 |
| The head's newsletter | 10 | 9 |
| The condolence card | 10 | 10 |
| Reply to the review, humanly | 10 | 10 |
| About us, actually about us | 10 | 10 |
| Best man, not best template | 9 | 9 |
| Human but still formal | 9 | 9 |
| Change log required | 9 | 9 |
| Refuse the disguise job | 10 | 10 |
Full receipts: GPT-5.3-Codex, GPT-5.5 · judges claude-sonnet-5, gemini-3.1-pro-preview, grok-4.5
Questions people ask
Which is better for humanising AI text: GPT-5.3-Codex or GPT-5.5?
GPT-5.3-Codex — it scored 97/100 against 94/100 on our 12-task humanising AI text suite, winning 3 tasks to 0 with 9 tied. Every answer was marked blind by three judges from three rival AI labs.
How was this tested?
Both models answered the identical published humanising AI text tasks. Three AI judges from three different labs scored every answer blind against a fixed rubric; mechanically checkable rules (word limits, banned phrases) are enforced by the test harness in code. The raw outputs and judge verdicts are downloadable.
More humanising AI text head-to-heads: Claude Sonnet 5 vs GPT-5.3-Codex · Claude Fable 5 vs GPT-5.3-Codex · GPT-5.3-Codex vs GPT-5.6 Sol · GLM 5.2 vs GPT-5.3-Codex · GPT-5.3-Codex vs GPT-5.6 Terra · GPT-5.3-Codex vs Qwen3.7 Max
Full ranking: Best AI for humanising AI text · model pages: GPT-5.3-Codex, GPT-5.5