Everyone wants to know if something was written by AI. Teachers checking student essays. Editors vetting freelance submissions. Employers screening job applications. Publishers trying to maintain standards.

The problem: AI detection is genuinely hard, and most tools oversell how reliable they are. Here’s what actually works in 2026, and what the limits are.

Why AI Detection Is Harder Than It Sounds

AI language models — including ChatGPT, Claude, Gemini, and others — generate text by predicting what words should come next. They produce fluent, coherent prose with varied sentence structure. The better the model, the harder it is to tell from human writing.

Early AI detectors looked for tell-tale patterns: repetitive sentence lengths, certain phrase constructions, statistical “flatness” in word choice. Those patterns were real in 2022. They’re much weaker now.

The additional problem: people use AI as an editing tool rather than a full generator. A human writes a rough draft, feeds it to ChatGPT for polish, and the result is a hybrid that confuses every detector on the market.

You should go into this with realistic expectations: no tool has a detection accuracy that justifies high-stakes decisions on its own.

The Best Detection Tools Available Right Now

GPTZero

URL: gptzero.me
Free tier: Yes (limited daily checks)
Best for: Educators, written assignments

GPTZero is the most widely used AI detection tool and one of the more reliable ones. It checks for “perplexity” (how surprising the word choices are — humans tend to be more surprising) and “burstiness” (how much sentence complexity varies — humans are more varied). It highlights specific passages it flags as likely AI.

The free version is usable. The paid tier adds batch uploads, which is useful if you’re checking multiple documents.

Accuracy: Better than most competitors. Still produces false positives on highly technical writing or non-native English speakers. Take the results as a data point, not a verdict.

Originality.AI

URL: originality.ai
Free tier: No (credit-based pricing, about $0.01 per 100 words)
Best for: Content publishers, SEO agencies

Originality.AI is geared toward publishers who need to vet freelance content at scale. It combines AI detection with plagiarism checking. Claims high accuracy, and third-party testing generally agrees it’s among the better performers.

Not free, but the per-word cost is low enough that checking occasional pieces is cheap.

Copyleaks

URL: copyleaks.com
Free tier: Limited
Best for: Enterprises and education institutions

Copyleaks integrates AI detection with plagiarism detection and has an LMS (Learning Management System) integration for schools. It’s used by universities and larger organizations. Solid track record, though enterprise pricing puts it out of reach for individuals.

Winston AI

URL: gowinston.ai
Free tier: Trial credits
Best for: Teachers and content agencies

Winston AI is another credible option with a clean interface. It gives a percentage likelihood of AI authorship and highlights suspect sections. Priced for individual and small-team use.

Built-in Detection: Turnitin

If you’re in academia, your institution may already use Turnitin, which added AI detection features in 2023. It’s only available through institutional subscriptions, but it’s worth knowing it exists if you’re an educator or student.

What “Good” Detection Actually Looks Like

When you run a document through any of these tools, you’ll get a percentage: “87% AI-generated” or “Likely human.” Here’s how to interpret that:

  • High confidence AI (80–100%): Worth a second look. Not automatic proof, but significant.
  • Middle range (40–70%): The tool isn’t sure. Often means editing or hybrid authorship. Treat with caution in either direction.
  • Low AI likelihood (0–30%): Probably human — but short documents, very technical writing, or heavily edited AI can land here too.

The tools are most reliable on longer pieces (500+ words). Short text gives them less data to work with.

Red Flags a Human Can Spot (That Tools Miss)

Experienced readers often catch AI writing on instinct. Here’s what you’re actually noticing:

Structural sameness. Every paragraph does the same thing: topic sentence, two supporting points, brief conclusion. Over and over. Human writers break this pattern constantly.

The “in conclusion” tell. AI loves summary conclusions that restate everything just said. Humans usually land differently.

No specific detail. AI generalizes. Human writers tend to include specific examples, weird details, things that only someone who lived through something would know.

Over-hedging. Phrases like “it’s important to note,” “it’s worth mentioning,” “there are several factors to consider” are AI habits. Humans use them occasionally. AI uses them constantly.

No opinion or personality. AI defaults to balance. It rarely takes a strong stand unless specifically prompted. Human writers, especially on anything they care about, have opinions.

The False Positive Problem (Serious Limitation)

Here’s the thing everyone using AI detectors needs to hear: false positives are real and they cause harm.

Studies have shown that non-native English speakers are disproportionately flagged as AI writers. People who write in a clear, structured style — because that’s how they learned to write — get flagged more often. Students with writing disabilities sometimes write in patterns that detectors read as artificial.

In 2023 and 2024, there were documented cases of students falsely accused of AI use based on detector results. Those accusations can have serious academic consequences.

The right way to use these tools: as a signal that prompts further investigation, not as proof of anything. If a detector flags work, the appropriate response is a conversation, not a punishment.

The Bottom Line

AI detection tools are better than nothing, but they’re not reliable enough to be the sole basis for a consequential decision. Use them as one input among several — alongside context, writing history, and direct conversation with the author.

The best detectors right now: GPTZero for free/low-cost individual use, Originality.AI for publisher workflows. Both are useful. Neither is infallible.

And remember: the goal isn’t catching people. It’s understanding what you’re working with so you can respond appropriately.