Claude Sonnet 5 vs GPT-5.5 for humanising AI text
Effectively a dead heat: 96–94
Same 12 humanising AI text tasks, marked blind by three rival labs. Claude Sonnet 5 took 2 tasks, GPT-5.5 took 0, 10 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 there, Just a quick note about invoice #2214 for £340 — it was due on 14 July and still shows as outstanding. I've attached the invoice again for your reference. Could you take a look when you get a chance? Thanks so much for your help with this.
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 | Claude Sonnet 5 | 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 | 9 | 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: Claude Sonnet 5, GPT-5.5 · judges gemini-3.1-pro-preview, gpt-5.6-terra, grok-4.5
Questions people ask
Which is better for humanising AI text: Claude Sonnet 5 or GPT-5.5?
Effectively a dead heat: Claude Sonnet 5 edged it 96/100 to 94/100 on our humanising AI text suite — too close to matter, so pick on price or the product you already use.
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 · GPT-5.3-Codex vs GPT-5.5 · Claude Fable 5 vs Claude Sonnet 5 · Claude Sonnet 5 vs GPT-5.6 Sol · Claude Sonnet 5 vs GLM 5.2 · Claude Sonnet 5 vs GPT-5.6 Terra
Full ranking: Best AI for humanising AI text · model pages: Claude Sonnet 5, GPT-5.5