Negative Prompts: How to Tell an AI What Not to Do

Published on September 3, 2025

Effective communication is as much about what you *don't* say as what you do. The same principle applies when communicating with artificial intelligence. While we often focus on telling the AI what we want it to produce, it's equally powerful to tell it what to avoid. This is the concept of negative prompting—a technique for adding constraints to steer the AI away from undesirable outputs.

Using negative prompts gives you a finer degree of control, helping you eliminate clichés, avoid certain topics, or enforce a specific style. It's an essential skill for anyone looking to move from basic prompting to advanced AI interaction.

Why Positive Instructions Aren't Always Enough

You might think you can control the output with positive instructions alone. For example, instead of saying "Don't use clichés," you could say "Use original and unique language." While this is a good practice, it doesn't explicitly forbid the unwanted behavior. AI models are trained on vast amounts of text from the internet, which is rife with clichés and common phrases. Without a specific instruction to avoid them, the AI may still fall back on these common patterns.

Negative prompts act as guardrails. They create clear boundaries for the AI, forcing it to find more creative and original pathways to fulfill your request.

Types of Negative Constraints You Can Use

Negative prompting is a versatile technique that can be applied in many ways. Here are some of the most common and effective types of constraints:

1. Content and Topic Avoidance

This is the most straightforward use case. You can instruct the AI to steer clear of certain subjects or themes.

2. Stylistic and Tonal Constraints

This is perfect for refining the voice of the AI. You can forbid specific tones or stylistic elements that don't fit your needs.

3. Word and Phrase Exclusion

If there are specific words or overused phrases you want to avoid, you can list them explicitly. This is a great way to de-jargon your content.

4. Structural and Formatting Constraints

You can also use negative prompts to control the format of the output, telling the AI what kind of structure to avoid.

Putting It All Together: A Complex Example

The true power of negative prompting comes when you combine it with strong positive instructions and a clear persona. Let's see how this works in a more complex scenario.

Goal: Generate a mission statement for a new sustainable clothing brand.

Initial Prompt:

This will likely produce something generic and full of clichés like "eco-friendly," "green future," or "changing the world."

Advanced Prompt with Negative Constraints:

This advanced prompt gives the AI a clear direction while also setting firm boundaries. The negative constraints force it to move beyond the obvious, resulting in a more unique and impactful mission statement.

Negative prompting is a subtle but powerful tool in your prompt engineering arsenal. By learning to tell the AI what not to do, you gain a new level of precision and control. It encourages the model to think more creatively and helps you produce content that is truly original and aligned with your specific vision. So, the next time you write a prompt, think not just about what you want, but also about what you want to avoid.