How Class Actions Get Certified Under Rule 23

A class action becomes a class action only when a federal judge says so. Under Rule 23 of the Federal Rules of Civil Procedure, the plaintiff proposing to represent the class must win certification: a court order finding that the case meets four threshold requirements plus one of three types-of-class tests. Certification is contested in nearly every significant case, because denial usually ends the litigation — individual claims are often too small to pursue alone, which is the reason the device exists.

What are the four prerequisite requirements?

Rule 23(a) sets them: numerosity — the class is so numerous that joining every member individually is impracticable, a threshold courts read loosely at a few dozen or more; commonality — there are questions of law or fact common to the class, which the Supreme Court in Wal-Mart v. Dukes (2011) sharpened into a requirement that at least one common question's resolution actually advance the litigation; typicality — the named plaintiff's claims arise from the same events and defects as the class's; and adequacy — the representative and class counsel will fairly protect the class's interests, which screens out plaintiffs with conflicts and lawyers with track-record problems.

What are the three types of class actions?

Rule 23(b) then requires the case to fit one of three molds. The most common is 23(b)(3), damage class actions — product defects, securities fraud, antitrust overcharges — where the court must find that common questions predominate over individual ones and that a class is the superior method for resolving them. Predominance is the heavy lift: if each member's damages depend on individual circumstances, the class fails. The alternative routes are 23(b)(1), limited to cases where separate suits would create incompatible standards for the defendant — think involuntary obligations — and 23(b)(2), civil-rights and injunctive cases where the defendant has acted on grounds generally applicable to the whole class.

• 23(b)(1): incompatible-rulings classes, relatively rare.
• 23(b)(2): injunction-only civil-rights classes; no damages jury.
• 23(b)(3): damages classes, requiring predominance and superiority.

What role does the merits question play?

Nominally none — the Supreme Court said in Eisen v. Carlisle & Jacquelin (1974) that certification is not a license to preview who wins. In practice, the predominance inquiry forces judges deep into the evidence: Wal-Mart v. Dukes reversed certification of 1.5 million employees precisely because the plaintiffs' discrimination theory could not be proved with common evidence, and Comcast v. Behrend (2013) decertified an antitrust class whose damages model did not match the liability theory. Defendants, for their part, sometimes argue for certification of narrow classes to lock in unfavorable rulings — the strategy is two-sided.

What happens after certification?

The certified case proceeds toward trial or settlement, with class members receiving notice and a chance to opt out of a damages class — their share of any recovery comes automatically unless they exclude themselves and sue alone. Settlements require court approval after a fairness hearing, and objectors may appeal. Appeals courts scrutinize certification orders closely under Federal Rule 23(f), which permits interlocutory review — and in cases like TransUnion v. Ramirez (2021), the Supreme Court has narrowed standing by requiring that every class member have suffered a concrete injury, trimming Article III's outer reach for no-injury classes.

LMH News publishes information, not legal advice. Procedure described follows Rule 23 and the cited Supreme Court decisions as of March 2026.