Passive Voice Checker: How to Tell When a Flag Actually Needs Fixing

The formula, per the UNC Writing Center: a form of "to be" (is, are, was, were, has been) followed by a past participle, with the actor either missing entirely or tucked into a "by" phrase at the end. "The uncertainty principle was formulated in 1927" is passive; "Werner Heisenberg formulated it in 1927" is the active version of the same fact, per University of Toronto's writing guide.

Structurally, passive voice moves the object of the action to the front of the sentence and pushes the actor to the back (or drops it). That's the actual mechanism — it has nothing to do with sentence length or how formal something sounds, which is a common mix-up.

APA's own style guidelines explicitly allow passive voice — they caution against overusing it, not using it at all — and recommend it specifically when the focus belongs on what was done rather than on who did it. Scribbr's summary of that guidance gives a clean example: "The projector was mounted on the wall" is the better sentence when the identity of whoever mounted it doesn't matter to your point.

University of Toronto's writing guide and the UNC Writing Center both add more cases where passive is the correct choice, not just an acceptable one: when the actor is genuinely unknown ("the cave paintings were made in the Upper Old Stone Age"), when the actor is irrelevant to your point, when you want to emphasize the object over the doer ("one hundred votes are required" emphasizes the vote count, not who's counting), and in lab reports and scientific writing, where passive voice traditionally keeps the emphasis on the experiment rather than the researcher — though UNC notes modern journals increasingly accept active voice here too.

The UNC Writing Center's clearest warning: passive voice can hide who's actually responsible for something, which matters when responsibility is the point. Its example contrasts the vague "a new system of drug control laws was set up" with the clearer active version that names the Lao People's Revolutionary Party as the actor — the passive version quietly drops the one fact that mattered.

It's also flagged as a sign of imprecise argument in essays and literary analysis — "Tom and Huck are portrayed as…" is weaker than "Twain portrays Tom and Huck as…" because it avoids stating who's doing the portraying. UNC specifically warns against passive voice in thesis statements, where precision matters most. Beyond those cases, the general pattern from both guides holds: passive constructions tend to run longer and less direct than the active version of the same idea, without a good reason.