Free GPTZero Checker
Test your writing against the perplexity and burstiness patterns GPTZero looks for — before you submit. Free, instant, and private: the instant check runs in your browser.
What GPTZero actually measures
GPTZero is best known for two signals. Perplexity measures how surprising your word choices are: language models pick the most statistically likely next word, which makes their output smooth but predictable. Burstiness measures variation — humans mix long, clause-heavy sentences with short, punchy ones, while AI tends toward uniform length. GPTZero also runs a trained classifier, so no outside tool can reproduce its exact score: this checker estimates both signals across 40 related patterns and lists exactly what triggered so you can fix it.
Lower your score the right way
When you score high, the fix is to add genuine variation rather than swap synonyms. Our free humanizer does this automatically, and our GPTZero guide covers the manual techniques.
Frequently asked questions
Is this an official GPTZero tool?
No — it's an independent, free checker that measures the same kinds of signals GPTZero uses (perplexity and burstiness). Use it to estimate risk and find what to fix before you run the real thing.
How does GPTZero detect AI text?
GPTZero is best known for two signals: perplexity (how predictable your word choices are) and burstiness (how much sentence length and complexity vary). AI text tends to be low-perplexity and low-burstiness — smooth and uniform. GPTZero also uses a trained classifier, so this checker estimates the same kinds of patterns rather than reproducing GPTZero's exact model.
Is it free and private?
Yes. There's no signup, and the instant check runs locally in your browser. The optional deep scan sends your text to our server to analyze it, and nothing is stored.
My text scored high — what now?
Use our free humanizer to rewrite the flagged passages so they read more naturally, then re-check. The goal is to raise perplexity and burstiness back into the human range.
Rewrite flagged passages for free
Humanize flagged text so it reads naturally, then re-check your score — no credit card required.
Get Started Free →