The 8 Best AI Detectors, Tested and Compared

Interestingly, false positives were not a big issue. Only 2/24 tests run on human-written content incorrectly flagged the text sample as AI-generated. All the AI detectors struggled the most with the hybrid human/AI content (for reasons explained below).

In the table below, you can see the actual AI content of each test article, followed by each tool’s analysis:

Ahrefs’ AI Detector

Score: 13/18

URL: https://ahrefs.com/writing-tools/ai-content-detector

Ahrefs AI Detector showed good accuracy across the board, with no false positives for human-written content, and good detection for AI content. It also managed to detect the specific model types used for the AI content: GPT-4o and Meta’s Llama.

By my criteria, it failed one out of nine tests, struggling to identify AI content that was blended with human writing. This is a known limitation of all AI detection tools (more on that below), and was true of all detection models.

Ahrefs AI detector is based on our own proprietary detection model, trained on a huge amount of web content. It’s unique among AI detectors because you can use it in conjunction with tons of other Ahrefs data points to see how content actually performs.

You can use Ahrefs’ AI detector to see:

• Which AI models are the best for creating high-quality content.
• How often your competitors publish AI content, and which models they use.
• How much AI content is present in a particular SERP, and how much effort you might need to invest to rank.
• How organic performance metrics correlate with different levels of AI use, like search traffic, keyword rankings, and backlinks.
• Whether AI content use correlates with traffic drops on particular pages or in particular subfolders.

Copyleaks

Score: 13/18

URL: https://copyleaks.com/ai-content-detector 

Copyleaks matched the top score, showing solid detection ability across both extremes of AI content. It proved especially effective at catching obvious AI writing, though it occasionally faltered in mixed or borderline passages.

GPTZero

Score: 12/18

URL: https://gptzero.me

GPTZero offered reliable results overall, with a clear strength in catching high-percentage AI content. However, it sometimes hesitated in assigning confident AI probabilities to mid-range or hybrid examples, slightly affecting its total accuracy.

Originality.ai

Score: 12/18

URL: https://originality.ai/ai-checker

Originality.ai performed well in most cases, accurately flagging AI-heavy text but showing a tendency to overestimate human authorship when faced with subtle or well-edited AI-generated material.

Scribbr

Score: 10/18

URL: https://www.scribbr.com/ai-detector/

Scribbr landed in the middle of the pack, handling clear-cut AI content reasonably well but displaying a drop in performance on more nuanced pieces, where its predictions tended to be inconsistent or overly cautious.

ZeroGPT

Score: 9/18

URL: https://zerogpt.com

ZeroGPT’s performance was uneven—it occasionally nailed high-AI content but frequently misclassified partial-AI and low-AI samples. The tool’s sensitivity seemed skewed toward extremes, resulting in a less balanced profile.

Grammarly

Score: 6/18

URL: https://www.grammarly.com/ai-detector

Grammarly’s free AI detector struggled with accurate AI detection, offering low-confidence or inaccurate predictions in many cases. It often failed to recognize clear signs of AI authorship and was unreliable on mixed or borderline content.

Writer

Score: 4/18

URL: https://writer.com/ai-content-detector/

Writer’s free AI detector scored the lowest, frequently misidentifying or entirely missing AI-generated material. It lacked precision across the board and provided little useful signal even when dealing with content that was 100% AI-written.