Every class action lawsuit in the federal court system exists because of one rule: Rule 23 of the Federal Rules of Civil Procedure. This is the rule that defines what a class action is, who can bring one, and how the process works from start to finish. If you have ever wondered why some lawsuits become class actions while others do not, Rule 23 is the answer.
Read our complete class action FAQ for answers to the most common questions.
What Is Rule 23?
Rule 23 is the section of the Federal Rules of Civil Procedure that governs class action lawsuits in United States federal courts. It lays out the requirements a case must meet before it can proceed as a class action, describes the different types of class actions that are allowed, and establishes the procedures courts must follow when managing these cases — including how settlements are reviewed and approved.
Think of Rule 23 as the rulebook for class actions. Without it, there would be no standardized way for groups of people with similar claims to join together in a single lawsuit.
The Four Requirements: Rule 23(a)
Before any case can become a class action, it must satisfy four basic requirements under Rule 23(a). All four must be met — if even one is missing, the court will not certify the class.
1. Numerosity
The class must be large enough that it would be impractical to bring every single member into court individually. There is no magic number — courts have certified classes as small as 25 people and as large as millions. The question is whether joining everyone together in separate lawsuits would be realistic. In most consumer cases involving defective products or data breaches, this requirement is easily met.
2. Commonality
There must be questions of law or fact that are shared across the entire class. In plain terms, the class members must all be dealing with the same core issue. For example, if a company sold a product with a hidden defect, every buyer shares the common question of whether the company knew about the defect and failed to disclose it.
3. Typicality
The claims of the people leading the lawsuit (called the class representatives or named plaintiffs) must be typical of the claims of the rest of the class. This means the representatives cannot have unusual circumstances that make their situation fundamentally different from everyone else’s. If the lead plaintiff bought a different version of the product or was harmed in a completely different way, their claims might not be typical enough.
4. Adequacy of Representation
The class representatives and their attorneys must be capable of fairly and adequately protecting the interests of the entire class. This means the representatives cannot have conflicts of interest with other class members, and the lawyers must have the experience and resources to handle the case competently. Courts take this requirement seriously because absent class members are relying on these people to protect their rights.
The Three Types of Class Actions: Rule 23(b)
Meeting the four requirements of Rule 23(a) is necessary but not enough. The case must also fit into one of three categories under Rule 23(b).
Rule 23(b)(1) — Risk of Inconsistent Results
This type applies when allowing individual lawsuits would create a risk of contradictory rulings that would put the defendant in an impossible position, or when a decision in one person’s case would effectively determine the outcome for everyone else. A common example is when multiple people have claims against a limited fund — if each person sued separately, early winners might exhaust the fund and leave nothing for later claimants.
Rule 23(b)(2) — Injunctive or Declaratory Relief
This type is used when the defendant has acted (or refused to act) in a way that affects the entire class, and the appropriate remedy is an order requiring the defendant to do something or stop doing something. Civil rights cases are the classic example — if a company has a discriminatory policy, a court order changing that policy benefits everyone in the class equally. This category is not designed for cases that are primarily about money damages.
Rule 23(b)(3) — Common Questions Predominate
This is the most common type of class action and the one most people encounter as consumers. It applies when the questions shared by the class are more significant than any questions that affect only individual members, and when a class action is a better way to resolve the dispute than having everyone sue separately.
Most consumer class actions — false advertising cases, data breach settlements, product defect claims, and price-fixing suits — fall under Rule 23(b)(3). This is also the only type where class members have the right to opt out and pursue their own individual claims instead.
Class Certification: The Make-or-Break Moment
One of the most important steps in any class action is class certification — the court’s decision about whether the case actually qualifies to proceed as a class action under Rule 23. This decision can make or break the entire lawsuit.
Under Rule 23(c), the court must make this determination at an early practical point in the case. The certification order must define who is in the class, identify the claims or issues involved, and appoint class counsel. If the court denies certification, the case cannot proceed as a class action, though the individual plaintiffs can still pursue their own claims.
Defendants fight hard against certification because a certified class dramatically increases the stakes of the litigation. A case that might involve $500 in individual damages can become a billion-dollar liability when millions of consumers are included as a class.
Notice to Class Members
If you have ever received a letter or email telling you that you are part of a class action, that notice exists because of Rule 23. For classes certified under Rule 23(b)(3), the court is required to send the best notice practicable to all class members who can be identified with reasonable effort.
The notice must clearly explain in plain language:
- What the lawsuit is about
- Who is included in the class
- What rights class members have, including the right to appear through their own attorney
- How and when to opt out if they choose to exclude themselves
- That the court’s judgment will be binding on everyone who stays in the class
Courts can use mail, email, or other methods depending on what is most likely to actually reach class members. The 2018 amendments to Rule 23 recognized that technology has changed how people receive information, and courts now have more flexibility in choosing how to deliver notice.
Settlement Approval: Rule 23(e)
No class action settlement can take effect without court approval. This is one of the most important protections Rule 23 provides, because class members who did not participate in the negotiation need someone looking out for their interests.
The settlement approval process works in two stages:
Preliminary Approval
The court reviews the proposed settlement to decide whether it is promising enough to justify sending notice to the class. This is not a final decision — it is more of a threshold check. If the court finds the settlement is plausible, it orders that notice be sent to class members so they can review the terms, file claims, opt out, or object.
Final Approval
After the notice period, the court holds a fairness hearing where it considers any objections and evaluates whether the settlement is fair, reasonable, and adequate. Under the 2018 amendments to Rule 23, the court specifically looks at four things:
- Whether the class representatives and their lawyers adequately represented the class during the litigation and negotiations
- Whether the settlement was negotiated at arm’s length (meaning both sides genuinely bargained rather than colluding)
- Whether the relief provided to the class is adequate given the costs, risks, and delays of going to trial
- Whether the settlement treats all class members equitably relative to each other
If the court is satisfied, it grants final approval and the settlement becomes binding on everyone in the class who did not opt out.
Objections and Opt-Outs
Rule 23 gives class members two important rights during the settlement process:
The right to object: Any class member can tell the court they believe the settlement is unfair. Objections must be specific — you need to explain what you disagree with and whether your concern applies just to you, to a subset of the class, or to everyone. The court considers objections at the final approval hearing.
The right to opt out: In Rule 23(b)(3) class actions, members can exclude themselves from the settlement entirely. If you opt out, you do not receive any payment but you keep the right to sue the defendant on your own. This right does not exist for classes certified under Rule 23(b)(1) or (b)(2).
Class Counsel: Rule 23(g)
Rule 23(g) requires the court to appoint class counsel — the lawyers who will represent the entire class. This is not automatic. The court must evaluate the attorneys’ experience, their knowledge of the relevant law, the work they have already done investigating the claims, and the resources they will commit to the case.
If multiple law firms compete for the role, the court must appoint the one best able to represent the class’s interests. Once appointed, class counsel’s primary duty is to the class as a whole, not to any individual member — including the named plaintiffs.
Attorney Fees: Rule 23(h)
Rule 23(h) governs how class action lawyers get paid. The court must approve any attorney fee award, and class members have the right to object to the fees requested. The court evaluates whether the fees are reasonable based on the results achieved for the class, the work done, and the risks the attorneys took in pursuing the case.
Fee awards typically range from 25 to 33 percent of the total settlement fund, though courts have discretion to award more or less depending on the circumstances.
Why Rule 23 Matters to You
Even if you never read the actual text of Rule 23, it affects you every time you receive a class action notice, file a claim for a settlement, or decide whether to opt out. The rule exists to balance two competing interests: giving large groups of people an efficient way to seek justice for small individual harms, while protecting the rights of class members who never asked to be part of the lawsuit in the first place.
Every settlement deadline you see, every notice you receive in the mail, and every claim form you fill out exists because Rule 23 requires it. Understanding the basics of this rule helps you make better decisions about your own rights when a class action comes your way.
By Steve Levine | Published: February 17, 2026
Legal Disclaimer
This article is a general educational overview of Rule 23 of the Federal Rules of Civil Procedure and does not constitute legal advice. Class action procedures can differ in state courts, and the application of Rule 23 varies by case. If you have questions about a specific class action or your rights as a class member, consult with a qualified attorney. OpenClassActions.org is a consumer news site and is not a law firm.