GPT-3.5 vs. GPT-4: What's the Difference?

GPT-3.5 or GPT-4? If you've used ChatGPT, you've probably noticed the model selector. But what's the actual difference?

The short version: GPT-4 is dramatically better at almost everything. But GPT-3.5 is faster and (was) cheaper. And in 2026, both are largely overshadowed by the GPT-5 family (with GPT-5.5 as the current flagship, April 2026).

In this article, I'll break down the key differences and give you clear recommendations on when to use which model.

1. What is GPT-3.5?

GPT-3.5 (also incorrectly called ChatGPT 3.5) is an LLM (language model) from OpenAI. It represents an improved version of GPT-3, which was released in June 2020.

More precisely, GPT-3.5 is not a single AI model, but consists of the language models code-davinci-002, text-davinci-002, and text-davinci-003.

GPT-3.5 is the default model of ChatGPT, available even to free users. You can try ChatGPT with GPT-3.5 for free here.

It's well suited for routine text work that is "everyday and not too demanding" and doesn't require ChatGPT plugins:

• Formatting (e.g., creating or modifying HTML tables or formatting a blog article)
• Changing between formal and informal tone
• Quick brainstorming
• Translations
• Changing capitalization
• Creating tables of contents
• Creating smaller code snippets
• etc.

The great advantage of GPT-3.5 lies in its speed. It generates responses noticeably faster than GPT-4.

However, GPT-4 is significantly more powerful:

2. What is GPT-4?

GPT-4 (also incorrectly called ChatGPT 4) is the flagship language model in ChatGPT. It has been available since mid-March 2023.

GPT-4 was trained with significantly more data than GPT-3.5. It can process more information and capture more complex relationships between words.

Since its release, I've tested it extensively and am impressed by the results. It performs significantly better than GPT-3.5 especially in the following tasks:

1. Math and logic
2. Data categorization
3. Programming
4. Text comprehension (e.g., understands idioms and complex instructions better)

Since November 2023, the "DALL·E", "Browsing", and "Advanced Data Analysis" (also called Code Interpreter) modes are also included in GPT-4. With DALL·E, you can generate images directly in ChatGPT.

With ChatGPT plugins, you can access third-party services and data and extend ChatGPT with new features. With Advanced Data Analysis, you can analyze documents, such as Excel files or text documents.

However, GPT-4 has three drawbacks:

First, as mentioned above, it could be slow. Second, errors occurred more often with GPT-4, for example, OpenAI's servers could be overloaded and generation could abort. Third, the number of queries for GPT-4 was initially limited to 40 per day (this limit no longer applies).

That's why I often used GPT-3.5 for simple text generation tasks back then. Today, these limitations are largely obsolete with GPT-4o and GPT-5.5.

3. GPT-3.5 and GPT-4 Comparison