The original title is: "TypeScript Abstract Classes vs Interfaces in 2026: Which to Reach For and When"

Short summary

This article explains when to use TypeScript interfaces versus abstract classes, framing the decision around whether shared code is needed. Interfaces define pure structural contracts with zero runtime cost, while abstract classes combine contracts with executable shared behavior. The author also covers hybrid patterns where abstract classes implement interfaces for maximum flexibility.

• •Interfaces offer compile-time enforcement with no runtime footprint; abstract classes provide shared behavior and state
• •The key decision factor: if the contract requires shared code, use an abstract class; otherwise use an interface
• •Hybrid patterns (abstract class implementing interface) separate contract from base implementation for flexibility

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