Checked against Anthropic’s announcement, Claude’s pricing page and the Claude app itself on 7 October 2026.
The short answer
Claude Sonnet 5.5 is Anthropic’s new mid-sized model, released on 28 September 2026. Anthropic says it runs more than 30% faster than Sonnet 5 and is better at everyday jobs like writing, documents, slides and spreadsheets.
Yes, you can use it for free. Claude’s pricing page lists Sonnet on the Free plan, and Tom’s Guide reports it replaced Sonnet 5 as the default model for Free and Pro users. You don’t need to do anything to get it.
What’s new in Sonnet 5.5
- Faster. Anthropic says it “runs 30%+ faster” than Sonnet 5.
- Better at everyday work. According to Anthropic, it is strongest at well-scoped everyday tasks, fixing bugs, and making polished documents, slides and spreadsheets.
- Close to Opus on many tasks. On one test of real workplace tasks (GDPval-AA), Anthropic says Sonnet 5.5 scored just two points below Opus 5.5. Opus is still the stronger choice for complex, open-ended work.
- Cheaper for developers. The API price stays at $2 per million input tokens and $10 per million output tokens, and Anthropic says most work costs up to 30% less than with Sonnet 5.
What we saw in the Claude app
We opened the model menu on a Claude Pro account on 7 October 2026. It now lists four models, each with a one-line description:
- Fable 5.1: “For your toughest challenges” (on Pro it needs usage credits)
- Opus 5.5: “For complex work and everyday tasks”
- Sonnet 5.5: “Most efficient for simpler tasks”
- Haiku 5.5: “Fastest for quick answers”
Update, 7 October 2026 (evening): Anthropic has now released Claude Haiku 5.5, calling it “the cheapest, fastest, and most capable small model” it has made. It is in the model menu too, described as “Fastest for quick answers”. We tested it against Sonnet 5.5 the same evening: see our Claude Haiku vs Sonnet test.
Not sure whether to use Sonnet or Opus? We gave both the same five everyday tasks and timed them: Claude Opus vs Sonnet: we tested both.
Is Claude Sonnet 5.5 free?
Yes. Here is what each plan gets, based on Claude’s pricing page:
| Plan | Sonnet 5.5 | Other models | UK price |
|---|---|---|---|
| Free | Yes | Haiku | £0 |
| Pro | Yes | Opus 5.5, Haiku; Fable 5.1 with usage credits | £18 a month (£15 paid yearly) |
| Max | Yes | Opus 5.5, Haiku, Fable 5.1 (up to 50% of weekly limits) | From £90 a month |
Free plan limits still apply, so heavy use will still hit the cap. Our guide Is Claude free? explains how the limit works and what Pro adds.
Should you use Sonnet 5.5 or Opus 5.5?
- On the Free plan: nothing to decide. Sonnet 5.5 is what you get, and Opus isn’t available.
- On Pro or Max, for quick, clear jobs like an email, a summary or a simple spreadsheet: try Sonnet 5.5. Anthropic says the model you pick affects how fast you use your allowance, and the app calls Sonnet 5.5 its most efficient model.
- For big, messy problems with lots of moving parts: stick with Opus 5.5.
Choosing a paid plan? See Claude Pro vs Max, or how Claude compares in Claude vs ChatGPT.
FAQ
When was Claude Sonnet 5.5 released?
Anthropic announced it on 28 September 2026.
Is Sonnet 5.5 better than Opus 5.5?
Not overall. Anthropic says it comes close on everyday workplace tasks, but Opus 5.5 is clearly stronger at complex, open-ended work.
Do I need to update the app?
On the web, no. Claude’s desktop app added Sonnet 5.5 support in an update on 27 September 2026, so if you don’t see it in the model menu, update the app.
Is there a Claude Haiku 5.5?
Yes. Anthropic released Claude Haiku 5.5 on 7 October 2026, and it appeared in the model menu on our Pro account that evening, described as “Fastest for quick answers”. Before that, the app showed Haiku 4.5.
How this update was made
- Checked against Anthropic’s Sonnet 5.5 announcement, Claude’s pricing page, Claude’s desktop changelog and the Claude app on 7 October 2026.
- Drafted with help from an AI writing assistant, then fact-checked and edited by Adsen.
- No affiliate links.
