Claude comes in three model tiers — Haiku, Sonnet, and Opus. The answer to "which should I use?" is simple: Sonnet for most things, Haiku for simple/bulk work, Opus only for truly hard problems. Here's how they differ and how to choose.
Reading the model names
Each name is tier + version.
- Haiku = the lightest, fastest tier.
- Sonnet = the balanced performance/cost tier.
- Opus = the most capable tier.
- The number (4.5/4.6/4.8) is the version — higher is newer. As of May 2026 the recommended lineup is Haiku 4.5 / Sonnet 4.6 / Opus 4.8.
How the three differ
- Haiku 4.5 — fastest and cheapest. Great for simple, high-volume work like classification, summarization, and extraction. Context (how much it handles at once) is about 200K tokens.
- Sonnet 4.6 — the best balance of quality and cost, so it's the recommended default for most tasks, from everyday chat to coding. Context ~1M tokens.
- Opus 4.8 — the latest and most capable model, for complex reasoning, hard coding, and deep analysis. Context 1M tokens. (It tends to be cited as the most capable model right now — exact benchmark numbers vary by source and version.)
Choosing in chat (claude.ai)
When picking a model in chat, Sonnet is enough for most things. Step up to Opus only when you're stuck or the problem is very complex. The free plan may limit which models you can pick; Pro/Max let you use higher tiers (plans/limits change — see the plan comparison).
Choosing in the API (developers)
In the API, mixing models by task difficulty is most cost-effective.
- Default to Sonnet 4.6.
- Explicitly call Haiku 4.5 for routine jobs (commit messages, log summaries, simple classification).
- Reserve Opus for the hard cases Sonnet can't solve.
Many analyses show this cuts cost a lot versus using Opus for everything. Claude Code switches models automatically by task. For pricing and keys, see the API key guide.
One-line summary
When in doubt, use Sonnet. Haiku when you need fast/cheap, Opus when it's truly hard.