Stable Diffusion Prompt Checker

Stable Diffusion is a powerful AI image generation tool. However, crafting good prompts can be challenging. It’s easy to make mistakes with brackets, commas, and formatting that prevent the AI from generating your desired image.

That’s where a prompt checker comes in handy! A prompt checker analyzes your prompt, fixes issues, and returns a corrected version that’s more likely to work with Stable Diffusion.

In this article, I’ll showcase my expertise on Stable Diffusion prompt checkers by providing insights into:

What is a prompt checker

A prompt checker is a tool, usually an online application or Python script, that checks Stable Diffusion prompts for errors.

It looks for problems like:

  • Unbalanced brackets
  • Incorrect comma placement
  • Improper formatting like spacing

And then it fixes these problems so your prompt will work properly when fed into Stable Diffusion.

Why prompt checkers are useful

Here are some of the key benefits of using a prompt checker:

  • Saves you time – Manually checking a complex prompt for errors can be tedious and time-consuming. A prompt checker does this instantly.
  • Prevents failed generations – Typos and formatting issues can make your prompt invalid, resulting in no image generated. A checker catches these problems before that happens.
  • Improves prompt engineering skills – Over time, you’ll make fewer mistakes as you learn what proper prompt formatting looks like.

Examples of prompt checkers

There are a few popular Stable Diffusion prompt checkers available:

  • Stable Diffusion Tools – An online application with a simple interface. Just paste your prompt and get a fixed version.
  • Prompt Hero – A site offering an extensive library of pre-made prompts you can browse.
  • Prompt Checker Python script – For coders, this Python script formats prompts. You run it in the command line or an IDE.

Out of these options, Stable Diffusion Tools is my personal recommendation because of its ease of use.

Using a prompt checker effectively

Here are some best practices to use a prompt checker effectively:

1. Check prompts routinely at first

When you’re new to crafting Stable Diffusion prompts, run every prompt through a checker before generating images. This trains your brain on proper formatting.

2. Pay attention to corrections

Don’t just blindly copy the fixed prompt. Read through it carefully and understand why changes were made. This develops your prompt engineering intuition over time.

3. Use checkers to diagnose failed prompts

If a prompt isn’t generating your expected image, run it through a checker. The corrections it makes may reveal why your prompt failed.

4. Double check weights and special characters

Prompt checkers are very good at catching bracket and comma errors, but can occasionally miss issues with weights and special characters. Give your corrected prompt a quick manual check too.

Prompt checker code walkthrough

For coders interested in understanding how prompt checkers work, let’s analyze some example Python code:

import re
import pyperclip

def fix_brackets(prompt):
  prompt = prompt.replace(" ]", "]") 
  prompt = prompt.replace(",]", "],")

  # Additional replacements
  return prompt

def fix_commas(prompt):
  prompt = prompt.replace(",,", ",")  
  return prompt

def fix_formatting(prompt):
  # Spacing and weight fixes
  return prompt

def prompt_checker(prompt):

  # Call fix functions
  prompt = fix_brackets(prompt)
  prompt = fix_commas(prompt)
  prompt = fix_formatting(prompt)


This code demonstrates:

  • Importing regex and clipboard libraries
  • Multiple helper functions that each fix a specific issue
  • A main function that runs the fixes in sequence
  • Printing and copying the final prompt

While simple, this approach allows easy troubleshooting and adding of new fix functions over time.


Using a prompt checker is a simple way to create better prompts and save frustration. Both coders and non-coders can benefit from these tools to improve their prompt engineering skills.

The most user-friendly option is Stable Diffusion Tools:

But those with Python knowledge can also build their own customized checker.

Whichever route you take, be sure to learn from the corrections prompt checkers give you. This will level up your prompting abilities over time!