Is GPT-4.1 Content Detectable?

OpenAI has unveiled GPT-4.1, a powerful new AI model optimized for coding and instruction following. 

According to OpenAI, this model “outperforms GPT‑4o and GPT‑4o mini across the board.” 

With support for an unprecedented one million token context window, GPT-4.1 marks a major leap in processing capacity, far beyond the previous GPT‑4o models’ 128,000-token limit. 

In light of this release, we evaluated GPT-4.1 to test the accuracy of our AI Detector.

This quick study looks at 1000 GPT-4.1-generated text results to answer whether GPT-4.1 can be detected.

Is GPT-4.1 AI Content Detectable?

• Yes — GPT-4.1 Text is Detectable with a 97.9% Accuracy for our 3.0.1 Turbo model and 94.5% Accuracy for our 1.0.0 Lite Model.

Try our AI Detector here.

Dataset

To evaluate the detectability of GPT-4.1, we prepared a dataset of 1000 GPT-4.1-generated text samples.

AI-Generated Text Data

For AI-text generation, we used GPT-4.1 based on three approaches given below:

1. Rewrite prompts: Generating the content by providing the model with a customized prompt along with some articles (probably generated by LLMs) as a reference from which to rewrite. (450 Samples)
2. Rewrite human-written text: Generating the content considering the provided prompt to bypass the AI Detection tool by rewriting the human-written text, which we fetched from an open-source dataset (325 Samples)
   
   1. One-Class Learning for AI-Generated Essay Detection
      
      1. Paper: https://www.mdpi.com/2076-3417/13/13/7901
      2. Dataset: https://github.com/rcorizzo/one-class-essay-detection
3. Write articles from scratch: Generating the articles from scratch based on the given topics, ranging from fictional and non-fictional, diverse domains such as history, medicine, mental health, content marketing, social media, literature, robots, and the future, etc. (225 Samples)

Evaluation

To evaluate the efficacy, we used our Open Source AI Detection Efficacy tool:

• AI Detector Used in this Study
• AI Detector Efficacy Testing Article
• Open Source AI Detection Efficacy Testing Tool

Originality.ai has three models — Model 3.0.1 Turbo, 1.0.0 Lite, and Multi Language for AI text detection.

• Version 3.0.1 Turbo — If your risk tolerance for AI is ZERO! It is designed to identify any use of AI, even light AI.
• Version 1.0.0 Lite — If you are okay with slight use of AI (i.e., AI editing).
• Multi-Language — Detect AI content across 30 languages.

Learn more about which AI detection model is best for you and your use case.

The open-source testing tool returns a variety of metrics for each detector tested, each of which reports on a different aspect of that detector’s performance, including:

• Sensitivity (True Positive Rate): The percentage of the time the detector identifies AI text correctly.
• Specificity (True Negative Rate): The percentage of the time the detector identifies human-written text correctly.
  Accuracy: The percentage of the detector’s predictions that were correct.
• F1: The harmonic mean of Specificity and Precision, often used as an agglomerating metric when ranking the performance of multiple detectors (a performance measurement that combines recall and precision to evaluate models).

If you'd like a detailed discussion of these metrics, what they mean, how they're calculated, and why we chose them, check out our blog post on AI detector evaluation. For a succinct snapshot,  the confusion matrix is an excellent representation of a model's performance.

Below is an evaluation of both models on the above dataset. 

Confusion Matrix:

Evaluation Metrics:

For this small test to reflect the Originality.ai AI Detector’s ability to identify GPT-4.1 content, we looked at the True Positive Rate, or the percentage of the time the model correctly identified AI text as AI out of a 1000-sample GPT-4.1 content. 

Model 3.0.1 Turbo:

• Recall (True Positive Rate) = 97.9%

Model 1.0.0 Lite:

• Recall (True Positive Rate) = 94.5%

Conclusion

Our study confirms that the content generated by GPT-4.1 AI-generated text is highly detectable with our AI detector. The Model 3.0.1 Turbo exhibited strong performance with 97.9% accuracy, while Model 1.0.0 Lite followed closely with 94.5%. 

These results highlight the effectiveness of the Originality.ai AI detector in identifying AI-generated content, even with the latest releases of popular AI models, like GPT-4.1, ensuring reliable detection across various text generation approaches.

Interested in learning more about AI detection? Check out our guides:

• AI Content Detector Accuracy Review
• A Meta-Analysis of AI Detection Studies
• How Does AI Content Detection Work?