In Angular, strict mode is a compiler option that enforces stricter rules and additional checks during the development and build process. It is designed to catch potential issues and help developers write more reliable and maintainable code. Strict mode can be enabled by setting the "strict": true flag in the Angular compiler options.

When strict mode is enabled, the Angular compiler applies the following stricter rules:

Strict Type Checking: TypeScript's strict type checking options are enabled, including stricter type inference, no implicit any types, and stricter null checks. This helps catch type-related errors at compile-time.

Enhanced Template Checks: Angular performs more thorough template checks to catch common mistakes and potential errors. It enforces stricter template type checking, including checking for template variable scopes, unused variables, and incorrect property bindings.

Strict Null Checks: The compiler applies stricter checks for null and undefined values. It helps prevent common errors caused by null or undefined values, such as null reference errors.

Strict Property Initialization: Angular enforces stricter rules for initializing class properties. All properties must be explicitly initialized, either in the constructor or at the declaration site, to avoid potential undefined values.

Strict Event Initialization: The compiler enforces stricter rules for initializing event emitters. Event emitters must be assigned with a new EventEmitter instance to avoid potential issues with uninitialized or null event emitters.

Enabling strict mode in Angular helps improve code quality, maintainability, and reduces the likelihood of runtime errors. It is recommended to use strict mode in Angular applications to leverage the benefits of these stricter rules and catch potential issues early in the development process.