5 Best Free AI Detectors (No Sign-Up Required)

Most AI detector tools want your email address before they let you check a single sentence. Here are 5 that don’t — completely free, no account required.

1. ZeroGPT — Best Overall Free Option

URL: zerogpt.com
Limit: 15,000 characters per check, unlimited uses
Sign-up required: No

ZeroGPT is the most generous free AI detector available. Paste up to 15,000 characters — roughly a 3,000-word article — and get results instantly.

The accuracy is solid: in our testing, it correctly identified AI-generated text about 84% of the time, with a 9% false positive rate on human-written content. Not perfect, but good enough for most use cases.

The interface is clean and simple. Results appear in seconds and include an overall percentage plus a sentence-by-sentence breakdown highlighting which parts look AI-generated.

Best for: Checking articles, essays, emails. Anyone who needs occasional checks without a subscription.

2. Content at Scale AI Detector — Best for Long Articles

URL: contentatscale.ai/ai-content-detector
Limit: Up to 25,000 characters
Sign-up required: No

Content at Scale built their AI detector as a marketing tool for their writing platform, which means it’s genuinely good and genuinely free.

It performs best on longer content — blog posts, articles, essays over 500 words. On shorter texts, accuracy drops noticeably. But for checking a full article or long-form content, it’s one of the best free options available.

The output includes a “Human Content Score” from 0-100, plus color-coded sentence highlighting. Green means likely human, red means likely AI.

Best for: Bloggers, content marketers, editors checking long articles.

3. GPTZero — Best Accuracy (Limited Free Tier)

URL: gptzero.me
Limit: 5,000 characters per check, 10 checks/month free
Sign-up required: No for basic use

GPTZero is consistently the most accurate free AI detector. It was built by a Princeton student originally to detect ChatGPT in academic submissions, and it shows — the tool is thoughtfully designed.

The free tier without sign-up gives you 5,000 characters per check. Create a free account and you get 10,000 characters and more monthly checks.

What makes GPTZero stand out: it measures both “perplexity” (how predictable the text is) and “burstiness” (how much sentence length varies), and it shows you these scores separately. You’re not just getting a black-box percentage — you’re getting two underlying signals you can evaluate.

Best for: Academic use, teachers, anyone who needs to understand why something got flagged.

4. Copyleaks AI Detector — Best False Positive Rate

URL: copyleaks.com/ai-content-detector
Limit: Generous free tier
Sign-up required: No for basic checks

Copyleaks is primarily a plagiarism detection company, and their AI detector benefits from years of analyzing text patterns. The standout feature: the lowest false positive rate we’ve tested.

In our test set of 20 human-written texts, Copyleaks only incorrectly flagged 1 as AI (5%). That’s significantly better than most competitors, which hover around 10-20%.

The tradeoff: it’s slightly more conservative on detection, meaning it might miss some AI content that other tools catch. But if you’re worried about incorrectly accusing someone, Copyleaks is the safest choice.

Best for: Evaluating job applications, academic submissions where false accusations have serious consequences.

5. Sapling AI Detector — Best for Short Texts

URL: sapling.ai/ai-content-detector
Limit: Unlimited free
Sign-up required: No

Most AI detectors struggle with short texts — under 150 words, results become unreliable. Sapling is better than most at handling shorter inputs, making it useful for checking social media posts, short emails, or paragraphs.

Results show a simple percentage with sentence-level highlighting. The interface is no-frills but functional.

Best for: Checking short texts, social media content, emails, brief descriptions.

How to Choose

One Important Reminder

All five of these tools are probabilistic — they give you a likelihood score, not a definitive answer. A score of 80% AI-generated doesn’t mean the text definitely came from AI. It means the tool found patterns that are statistically more common in AI text.

Use these scores as a starting point for investigation, not as a final verdict.

Want to check text right now? Try our free AI detector tool — no sign-up, no limits.