A demurrer challenges whether an entire claim is legally valid; a motion to strike removes specific improper material from a filing without touching the claim itself. That’s the heart of the demurrer vs. motion to strike comparison. One can end a case before discovery begins. The other just cleans up the paperwork. They often show up at the same early stage of a lawsuit, and a defendant sometimes files both at once, but they answer very different questions and produce very different outcomes.
What a Demurrer Actually Does
A demurrer is a formal challenge to the legal sufficiency of the opposing party’s complaint. The word itself is largely historical. Federal courts and the vast majority of states now call this a motion to dismiss for failure to state a claim, governed by Federal Rule of Civil Procedure 12(b)(6). A few states, notably California and Virginia, still use “demurrer,” but the function is identical.1Legal Information Institute. Federal Rules of Civil Procedure Rule 12
The argument goes like this: even if everything the plaintiff alleges actually happened, those facts don’t add up to something the law recognizes as a valid claim. The motion doesn’t dispute the facts. It says the facts don’t matter because no legal theory supports them. If someone sues a neighbor because they find the neighbor’s house paint ugly, the neighbor can move to dismiss. Ugly paint isn’t something you can sue over, no matter how thoroughly the complaint describes the shade.
When a court considers this kind of motion, it looks only at the complaint itself and treats every factual allegation as true. Discovery hasn’t started. The judge isn’t weighing evidence or predicting who will win at trial. The question is whether the story told in the complaint, taken at face value, describes a situation the law provides a remedy for. Courts apply what’s often called the plausibility standard: the complaint must contain enough factual detail to make the claimed legal violation plausible, not just theoretically possible. Bare conclusions like “the defendant acted negligently” won’t survive on their own. The complaint has to describe what the defendant did and why that conduct amounts to a legal wrong.
What a Motion to Strike Actually Does
A motion to strike asks the court to remove specific material from a pleading. Where a motion to dismiss challenges an entire claim, a motion to strike targets individual sentences, paragraphs, or defenses that don’t belong. Rule 12(f) lets the court strike material that is redundant, immaterial, irrelevant, or scandalous.1Legal Information Institute. Federal Rules of Civil Procedure Rule 12
Think of it as editing rather than rejecting. If a breach-of-contract complaint includes a paragraph describing the defendant’s unrelated personal life in unflattering terms, the defendant can move to strike that paragraph. The contract claim continues; the irrelevant attack gets cut. If a plaintiff requests damages the law doesn’t allow for the claim being asserted, a motion to strike can remove that request.
Motions to strike aren’t just a defendant’s tool. Courts can also strike insufficient affirmative defenses from a defendant’s answer, so a plaintiff who receives an answer full of boilerplate defenses with no factual support can move to strike them. The rule applies to any party challenging any pleading, and the court can strike material on its own initiative.1Legal Information Institute. Federal Rules of Civil Procedure Rule 12
One caution: federal courts view motions to strike with disfavor. Judges consider removing material from a pleading a drastic step, and many motions to strike are filed as delay tactics. If there’s any doubt about whether the challenged material might be relevant, courts tend to deny the motion and let the case move on. A well-targeted motion aimed at genuinely prejudicial content or defenses with no factual basis can still be worth filing, but it has to be precise. A motion used as a fishing expedition or a substitute for a motion to dismiss will go nowhere.
The Key Differences
The most fundamental distinction is scope. A demurrer or motion to dismiss is a broad challenge to an entire claim, asking the court to throw it out because, as a matter of law, it doesn’t hold up. A motion to strike is surgical. It leaves the claim intact and removes offending material from the document.
The goals differ. A successful motion to dismiss can end a case or eliminate a claim entirely. A successful motion to strike just tidies up the pleading. The lawsuit keeps going, only with the improper content removed.
The stakes differ, too. A motion to dismiss is one of the most consequential filings in a lawsuit; it can resolve the case before discovery starts. Motions to strike rarely carry that kind of weight, which is part of why courts are less enthusiastic about them.
When You’d File Each, or Both
File a motion to dismiss when the complaint, read generously in the plaintiff’s favor, still doesn’t describe conduct the law provides a remedy for. That’s the whole point of the motion. It’s the tool for saying the case shouldn’t proceed at all.
File a motion to strike when a specific piece of the pleading is out of place: an inflammatory paragraph that has nothing to do with the claim, a damages request the law doesn’t allow, a boilerplate affirmative defense with no factual grounding. The rest of the pleading may be fine. You just want the specific offending language gone.
A defendant facing a weak complaint that also contains an inflammatory paragraph might file both at once: one motion to dismiss the claim itself, another to strike the objectionable language if the claim survives. Nothing prevents pairing them, and the two motions do independent work.
Deadlines and the Waiver Trap
Timing matters with both motions, and missing a deadline can cost you a defense permanently. Under the federal rules, a defendant generally has 21 days after being served with the complaint to respond. Both a motion to dismiss and a motion to strike must be filed before the defendant submits a formal answer.1Legal Information Institute. Federal Rules of Civil Procedure Rule 12 For a motion to strike where no responsive pleading is required, the deadline is 21 days after being served with the pleading. State courts often set different timelines, so check the local rules.
Rule 12 also contains a waiver trap. If you file a motion to dismiss and leave out certain defenses, you lose them for good. The defenses subject to this use-it-or-lose-it rule are lack of personal jurisdiction, improper venue, insufficient process, and insufficient service of process. Omit any of them from your first Rule 12 motion and they’re gone.1Legal Information Institute. Federal Rules of Civil Procedure Rule 12
Not every defense faces this risk. Failure to state a claim, failure to join a required party, and lack of subject-matter jurisdiction can all be raised later in the case. Subject-matter jurisdiction can be challenged at any point, even on appeal. But the four procedural defenses above? You get one shot.
After the Court Rules
If the court grants a motion to dismiss, it has found the complaint legally insufficient. That doesn’t necessarily end the case. Courts frequently grant the motion “with leave to amend,” giving the plaintiff a chance to fix the problems and refile. The court should freely give leave to amend when justice requires it,2Cornell Law School. Federal Rules of Civil Procedure Rule 15 – Amended and Supplemental Pleadings so most first-time dismissals aren’t fatal. If the court decides the defect can’t be fixed, it grants the motion without leave to amend and the claim is dismissed with prejudice. The plaintiff can’t refile. That outcome is more common when the plaintiff has already had multiple chances to amend or when the legal theory itself is fundamentally flawed rather than just poorly pled.
If the motion is denied, the court has found the complaint legally sufficient. The defendant then has 14 days from notice of the decision to file an answer, unless the court sets a different deadline.1Legal Information Institute. Federal Rules of Civil Procedure Rule 12 The case moves into discovery.
A granted motion to strike simply removes the targeted material from the pleading, and the case continues based on the cleaned-up document. A denied motion leaves everything as written. Either way, the lawsuit itself isn’t in jeopardy. A motion to strike never threatens to end a case the way a motion to dismiss can.
A Note on Anti-SLAPP “Special Motions to Strike”
If you’ve encountered the phrase “motion to strike” in a free speech or defamation context, you may be thinking of something different. More than 30 states have anti-SLAPP laws (SLAPP stands for “strategic lawsuit against public participation”) that let defendants quickly dispose of lawsuits targeting constitutionally protected speech. These are sometimes called “special motions to strike,” but they have almost nothing in common with the Rule 12(f) motion described above.
An anti-SLAPP motion seeks to dismiss the entire claim on the ground that the lawsuit retaliates against protected activity like public commentary or petitioning the government. In many states, filing the motion automatically pauses discovery, the burden shifts to the plaintiff to show the claim has merit, and the losing party may have to pay the winner’s attorney fees. Whether these state laws apply in federal court remains unsettled and varies by circuit. If your situation involves a claim aimed at speech or public participation, the anti-SLAPP analysis is separate from anything in Rule 12.