About this site
PassiveVoiceChecker is a free, browser-based passive voice checker with a sourced guide cluster and an original dataset, the Passive Voice Index. It is published by a small independent editorial team and funded by advertising and affiliate links.
The engine
The checker is a rule-based JavaScript module. It finds a form of be or get followed, within three words, by a past participle, and sorts each hit into one of three tiers: passive, probably passive (the participle could be an adjective) and adjective, not passive (emotive and stative participles such as interested or tired, which are shown but not counted). It looks for a “by” agent, re-inflects the verb to produce an active rewrite, and gives a verdict on whether the passive is likely to be justified.
We use a rule-based engine rather than a language model because detection is a pattern-matching problem: rules are deterministic, explainable, cost nothing to run, and let your text stay on your device.
Accuracy
The engine ships with a labelled test set of 151 sentences — true passives, probable passives, adjectival look-alikes and active sentences that fool simpler checkers. The current build scores 100% on passive-or-not and 98% on the exact tier, and the build fails if the first number drops below 95%. The test set and script are in the site’s source. Real prose is messier than a test set; treat every flag as a question.
The Passive Voice Index
The Index runs the same engine over 146 public-domain and U.S. government documents — every presidential inaugural address, 65 State of the Union messages, the founding documents and 18 classic books — and publishes the results as a dataset under CC BY 4.0. It exists so that “how much passive voice is normal?” has an answer with numbers behind it.
Sources
Grammar claims on this site cite a named authority — the Purdue OWL, the federal plain-language guidelines, APA Style, Yoast’s published methodology, or the vendor’s own documentation — and the sources are listed at the foot of each guide. We do not publish statistics we did not measure ourselves.
Funding
The site shows Google AdSense advertising and may use affiliate links to writing tools, marked as such. Affiliate relationships do not change what we say about a product; the comparison page rates the tools we are paid by exactly as it rates the ones we are not.
Privacy
The checker runs entirely in your browser; nothing you paste is sent to us. See the privacy page for what the advertising and analytics scripts collect.
Contact
Corrections, questions and requests to use the Index data: see the contact page.