Choosing Between Opus, Sonnet, and Haiku
Anthropic's Claude AI comes in three sizes. Here's how to pick the right one without wasting money or time.
Three Sizes of the Same Brain
Imagine you could buy a car in three sizes: a heavy-duty truck, a family sedan, and a zippy little scooter. They all get you where you need to go, but each one is built for a different kind of trip. That's exactly how Anthropic designed Claude.
Opus is the truck. It's the biggest, smartest, and slowest. It handles the hardest jobs that need deep thinking. Sonnet is the sedan. It's the all-rounder — fast enough, smart enough, and good for most everyday work. Haiku is the scooter. It's tiny, lightning-fast, and dirt cheap to run, but it can't carry the heavy loads.
All three are the same AI made by the same company, just tuned differently. You pick based on what you're trying to do.
Picking the Wrong One Costs You
If you always reach for the biggest model, you burn money and time on jobs that didn't need it. If you always reach for the smallest, you get sloppy answers on tasks that needed real thought. Picking smartly is the difference between a tool that pays for itself and one that bleeds cash.
It also matters for speed. A user waiting 30 seconds for a chatbot reply is going to close the tab. The same task might take 2 seconds on a smaller model and feel instant. So choosing well is about cost, quality, AND speed — three knobs that have to be balanced together.
💡 Key Insight
Most people reach for the biggest model by default and waste 80% of their AI budget. The trick is to use the smallest model that can still do the job well. Start with Haiku. If the answer is bad, bump up to Sonnet. Only reach for Opus when nothing else works.
Meet the Three Models
Each Claude model is built for a different kind of job. Here's how to think about them:
Opus — The Heavy Lifter
The biggest and most thoughtful model. Best for hard reasoning, long documents, complex coding, and tasks where getting the right answer matters more than getting it fast. The most expensive of the three.
Sonnet — The All-Rounder
The middle option. Good at almost everything — chat, summaries, code, analysis. Faster and cheaper than Opus, smarter and slower than Haiku. The safe default for most apps.
Haiku — The Speed Demon
The smallest and fastest. Great for simple tasks like classifying text, short replies, tagging, and bulk work. Cheap enough to run at scale, but weaker on tough problems.
Here's a simple rule of thumb for picking one:
- Need deep thinking? Use Opus.
- Need a balanced helper? Use Sonnet.
- Need fast and cheap? Use Haiku.
Switching Models in Code
The same code works with any of the three models — you just change the model name. This is how you build an app that picks the right one automatically:
# Pick the right Claude model for the job import anthropic client = anthropic.Anthropic() def ask_claude(prompt, difficulty="medium"): # Choose a model based on how hard the task is if difficulty == "easy": model = "claude-haiku-4-5" # fast + cheap elif difficulty == "medium": model = "claude-sonnet-4-5" # balanced else: model = "claude-opus-4-1" # deepest thinking response = client.messages.create( model=model, max_tokens=1024, messages=[{"role": "user", "content": prompt}] ) return response.content[0].text # Easy job: tag a customer review print(ask_claude("Is this review positive? 'Love it!'", "easy")) # Medium job: summarize a meeting # Hard job: review a legal contract for risks
The output, the API calls, and the way you build the app are all the same. The only thing that changes is the model name. That makes it easy to test all three on the same task and see which one gives the best balance of cost and quality.
Knowledge Check
Test what you learned with this quick quiz.