Rule 23 of the Federal Rules of Civil Procedure is the rule that governs class actions in federal court. It lets one person or a small group sue on behalf of a much larger group harmed the same way, and it sets out who qualifies to bring such a case, how a court decides whether to allow it, what notice absent members receive, and how any settlement gets approved.1Legal Information Institute. Federal Rules of Civil Procedure Rule 23
The rule exists because some disputes involve too many affected people for individual lawsuits to be workable. Combined into one proceeding, claims that would never be brought alone can be resolved together.
The Four Requirements Every Class Must Meet
Rule 23(a) sets four prerequisites. All four must be satisfied. Missing one is enough for a court to deny certification.1Legal Information Institute. Federal Rules of Civil Procedure Rule 23
Numerosity
The class has to be large enough that joining every member as a named party would be impractical. Rule 23 sets no fixed number, but courts generally treat groups of forty or more as presumptively large enough. Smaller classes sometimes qualify when members are geographically scattered or hard to identify, and larger groups can fail if the members are easy to join. What matters is whether individual joinder would be unworkable, not the headcount.
Commonality
Class members must share at least one question of law or fact. The Supreme Court raised the bar for this requirement in Wal-Mart Stores, Inc. v. Dukes, holding that merely raising common questions is not enough. The shared question must be one where a classwide proceeding can “generate common answers apt to drive the resolution of the litigation.”2Justia. Wal-Mart Stores, Inc. v. Dukes, 564 U.S. 338 (2011) A single true-or-false determination has to resolve something central to every member’s claim. Differences within the class that prevent that single answer can sink certification here.
Typicality
The representative’s claims must arise from the same conduct or events that harmed the rest of the class. Same defective product, same corporate policy, same misleading advertisement. If the representative’s situation is too unusual, pursuing their own claim won’t advance the group’s interests.
Adequacy of Representation
The named plaintiffs and their lawyers must be capable of protecting every absent class member’s interests. Courts look at whether the representative has any conflict with the rest of the class, and whether the legal team has the experience and resources to run complex, large-scale litigation. This is the requirement that catches situations where a representative might accept a quick, cheap settlement that helps them personally and shortchanges everyone else.
The Three Categories of Class Action
Meeting the four prerequisites is only the first step. The case must also fit into one of three categories under Rule 23(b). The category determines how the case proceeds and, critically, whether class members can opt out.
Rule 23(b)(1): Risk of Inconsistent Rulings
This category covers cases where separate individual lawsuits would put the defendant in an impossible position, or where a limited pool of money could be drained by the first claimants and leave nothing for the rest. Pension fund assets and insurance proceeds are the classic examples. Consolidating everyone into a single class ensures a coherent result. Members of a 23(b)(1) class generally cannot opt out.1Legal Information Institute. Federal Rules of Civil Procedure Rule 23
Rule 23(b)(2): Injunctive or Declaratory Relief
When the defendant has acted the same way toward the whole class and the remedy sought is a court order changing that behavior, the case fits here. Civil rights cases are the prototype: a school district with a discriminatory policy, an employer with a company-wide practice that violates federal law. The relief binds everyone uniformly, so the rule does not require individual opt-outs.
Rule 23(b)(3): Monetary Damages
This is what most people picture when they hear “class action.” It covers suits for money damages and dominates consumer protection, securities fraud, and antitrust litigation. Certification under 23(b)(3) requires two showings beyond the Rule 23(a) prerequisites. Common questions must predominate over individual ones, and a class action must be the superior method for resolving the dispute compared to other alternatives.
On superiority, the court weighs whether individual members have a strong interest in controlling their own suits, whether related litigation is already underway, whether concentrating claims in one forum makes sense, and how manageable the class action would be. Unlike the other two categories, a 23(b)(3) class must receive formal notice and an opportunity to opt out.
The Certification Order and Class Counsel
Rule 23(c)(1) requires the court to decide certification at an early practicable time after the case is filed. The certification order defines the class, spells out the claims and defenses to be resolved on a classwide basis, and identifies who will be bound by any eventual judgment.
Certification is not permanent. If circumstances change or new information shows the requirements are no longer met, the court can alter or revoke it any time before final judgment. Rule 23(c)(4) also lets the court certify a class as to particular issues only. A court can resolve one common question — say, whether a product was defectively designed — on a classwide basis while leaving individualized questions like damages for separate proceedings.
When a class is certified, the court appoints class counsel under Rule 23(g). The appointment weighs how much work counsel has already done identifying and investigating the claims, counsel’s experience with class actions and similar complex litigation, counsel’s knowledge of the applicable law, and whether the team has the resources to see the case through. Because class counsel will represent people who never chose them, the court acts as a gatekeeper.
Notice and the Right to Opt Out
For a class certified under Rule 23(b)(3), the court must direct the best notice practicable to every member who can be identified through reasonable effort. That usually means individual mailings or emails to known addresses, supplemented by publication for members who cannot be identified. The notice must be in plain language and must explain the nature of the case, the class definition, and what the class is seeking.
The opt-out provision is the most consequential part. Any class member who wants to bring their own individual lawsuit instead can request exclusion, and the notice must state exactly how and when to do so. Rule 23 itself sets no specific opt-out deadline. The court sets one case by case, and 30 to 60 days is common in practice. If you stay in the class and do nothing, the eventual judgment binds you, win or lose, and you cannot sue the defendant separately over the same issue. Members who remain also have the right to hire their own attorney to monitor the case, though few do.
Classes certified under 23(b)(1) or 23(b)(2) do not carry the same opt-out right, because those categories involve indivisible relief where letting individuals exit would defeat the purpose of proceeding as a class.
Settlement Approval
A class action cannot be settled, voluntarily dismissed, or compromised without court approval. Absent class members had no seat at the negotiating table, so the judge has to make sure the deal is fair to them. The 2018 amendments structured this review by listing specific factors the court must weigh under Rule 23(e)(2):
- Whether the class representatives and class counsel adequately represented the class throughout the litigation and negotiations.
- Whether the settlement was the product of arm’s-length, genuinely adversarial bargaining rather than a sweetheart deal between the lawyers on both sides.
- Whether the relief is adequate given the costs, risks, and delays of trial, and whether the proposed method of distributing money, the attorney fee arrangement, and any side agreements hold up to scrutiny.
- Whether the settlement treats class members equitably relative to one another.
Class members must be notified of the proposed settlement and given a chance to object. Any member can argue the deal is inadequate or that the requested attorney fees are excessive. Fee awards typically run 25% to 33% of the total recovery, though courts approve fees above and below that range depending on the case. Under Rule 23(e)(5)(B), no payment can be made in connection with withdrawing an objection or abandoning an appeal without court approval, a rule aimed at objectors who use their objections to extract side payments.
If the court rejects the settlement, the parties return to negotiation or move toward trial.
Appealing a Certification Decision
Class certification often decides the case in practical terms. A defendant facing a certified class of thousands frequently has more incentive to settle than to try the case, so the ruling can effectively end the litigation. Rule 23(f) lets either side ask the court of appeals for permission to hear an immediate appeal without waiting for final judgment.
The window is short. You have 14 days after entry of the certification order to file a petition for permission to appeal. If the federal government is a party, the deadline extends to 45 days. The court of appeals has complete discretion whether to take the case; there is no right to an interlocutory appeal. Permission is most likely when the certification ruling turns on a novel or unsettled question of law, or when the decision is going to end the litigation one way or the other.
What Filing Does to the Statute of Limitations
Filing a class action pauses the statute of limitations for every member of the proposed class. The rule comes from the Supreme Court’s decision in American Pipe & Construction Co. v. Utah.3Legal Information Institute. American Pipe and Construction Co. v. Utah, 414 U.S. 538 Without tolling, absent class members would have to file protective individual suits while waiting to see whether the class gets certified, which would defeat the efficiency the class action device is meant to provide.
Tolling runs from the filing of the class action until the court denies certification or the class otherwise falls apart. At that point each member’s individual clock starts again with whatever time they had left. If you had 30 days remaining when the class action was filed, you get those 30 days back to file your own suit.
Two limits are worth knowing. American Pipe tolling does not pause statutes of repose, which are hard outer deadlines measured from the defendant’s conduct rather than from discovery of the harm. And the Supreme Court has held that the doctrine does not toll the limitations period for a follow-on class action; it protects individual follow-on claims only, not successive attempts at class certification.
When Class Actions Belong in Federal Court
The Class Action Fairness Act of 2005, known as CAFA, expanded federal jurisdiction over large class actions. Federal courts have jurisdiction over any class action where the total amount in controversy exceeds $5 million and at least one class member is a citizen of a different state than at least one defendant.4Office of the Law Revision Counsel. 28 U.S. Code 1332 – Diversity of Citizenship; Amount in Controversy; Costs That “minimal diversity” standard is deliberately lower than the complete diversity normally required for federal jurisdiction.
CAFA carves out exceptions for genuinely local disputes. The local controversy exception requires a federal court to decline jurisdiction when more than two-thirds of the proposed class are citizens of the state where the case was filed, at least one significant defendant is also a citizen of that state, and the principal injuries occurred there. A discretionary exception applies when between one-third and two-thirds of class members are citizens of the filing state, letting federal courts weigh factors like whether the claims involve matters of national interest or whether the pleading was structured to avoid federal jurisdiction.