CSS Architecture: BEM, SMACSS, and More

In the world of web development, CSS architecture plays a crucial role in maintaining clean and scalable code. Two popular methodologies, BEM (Block Element Modifier) and SMACSS (Scalable and Modular Architecture for CSS), have gained significant traction among developers. In this blog post, we will explore these methodologies and delve into other emerging approaches that can help streamline your CSS codebase.

CSS Architecture: BEM, SMACSS, and More

CSS Architecture: BEM, SMACSS, and More

CSS architecture plays a crucial role in web development, ensuring clean, scalable, and maintainable code. With the increasing complexity of web applications, it's essential to adopt a structured approach to CSS to avoid code bloat, specificity issues, and the dreaded "spaghetti code" syndrome. In this article, we will explore two popular CSS architecture methodologies - BEM (Block Element Modifier) and SMACSS (Scalable and Modular Architecture for CSS) - along with other notable approaches.

Introduction to CSS Architecture

CSS architecture refers to the organization and structure of CSS code within a project. It involves establishing guidelines, naming conventions, and methodologies that allow developers to write CSS in a modular, reusable, and maintainable manner. A well-designed CSS architecture helps streamline development, collaboration, and future updates.

BEM: Block Element Modifier

BEM is a popular CSS architecture methodology that emphasizes component-based development. It provides a clear and consistent naming convention for CSS classes, making it easier to understand and maintain the codebase.

Key Principles of BEM

  1. Block: The highest-level component that represents a standalone entity on a page. Examples of blocks could be a header, navigation, or a button.

  2. Element: A part of a block that has no standalone meaning. Elements are always scoped to a specific block and are denoted by two underscores "__" in their class names.

  3. Modifier: A variation or state of a block or element. Modifiers are used to change the appearance, behavior, or state of a block or element and are denoted by two hyphens "--" in their class names.

BEM Naming Convention

The BEM naming convention follows a strict pattern: block__element--modifier. Let's consider an example of a button component:

.button {
  /* Styles for the button block */

.button__text {
  /* Styles for the text element within the button block */

.button--primary {
  /* Styles for the primary modifier of the button block */

Using BEM, each class name provides clear context and hierarchy, making it easier to understand the relationships between different components. This methodology promotes reusability and reduces the chances of style conflicts.

SMACSS: Scalable and Modular Architecture for CSS

SMACSS is another popular CSS architecture methodology that focuses on categorizing CSS rules into five different categories: Base, Layout, Module, State, and Theme. It provides guidelines for structuring CSS code and encourages separation of concerns.

SMACSS Categories

  1. Base: The base category includes styles that apply to all elements, such as typography, reset styles, and global box-sizing rules.

  2. Layout: The layout category deals with the overall structure and positioning of major sections of a page. It includes styles for grids, containers, and layout-related classes.

  3. Module: The module category represents reusable, standalone components. Modules are self-contained and should not depend on other modules or the layout.

  4. State: The state category defines styles that change the appearance or behavior of a module or element based on a specific state, such as hover, active, or disabled.

  5. Theme: The theme category allows for different visual variations of modules or elements. It helps create consistent design patterns for different themes or sections of a website.

Applying SMACSS Principles

To apply SMACSS principles, you can organize your CSS files into separate folders or files based on the categories mentioned above. For example:

- base/
  - typography.css
  - reset.css
  - box-sizing.css

- layout/
  - grid.css
  - container.css

- module/
  - button.css
  - card.css

- state/
  - hover.css
  - active.css
  - disabled.css

- theme/
  - light.css
  - dark.css

By categorizing CSS rules, SMACSS helps developers understand the purpose and scope of each CSS file or class, enabling easier maintenance and scalability.

Other CSS Architecture Methodologies

While BEM and SMACSS are widely adopted CSS architecture methodologies, several other approaches exist, each with its own strengths and considerations. Let's briefly explore a few notable ones:

OOCSS: Object-Oriented CSS

OOCSS aims to promote reusability and modularity by separating structure from skin. It encourages creating CSS classes that represent reusable objects and separate visual styles into separate classes. OOCSS can be a powerful approach for large-scale projects with complex UI requirements.

Atomic CSS

Atomic CSS, also known as Functional CSS, takes a different approach by focusing on small, single-purpose utility classes. Instead of creating specific classes for each component, Atomic CSS provides a set of utility classes that can be combined to achieve desired styles. This approach can lead to smaller CSS file sizes and encourages code reusability.

ITCSS: Inverted Triangle CSS

ITCSS is a scalable and maintainable CSS architecture that emphasizes the order and specificity of CSS rules. It organizes CSS code based on a specific hierarchy, starting from generic styles and gradually moving towards more specific styles. ITCSS helps prevent specificity issues and encourages a modular and scalable approach to CSS.


CSS architecture is crucial for building scalable, maintainable, and reusable CSS code. By adopting methodologies like BEM and SMACSS, developers can structure their CSS code in a way that promotes modularity, reusability, and ease of maintenance. Additionally, considering other approaches like OOCSS, Atomic CSS, and ITCSS can provide valuable insights into alternative ways of organizing CSS code. Choose the architecture that best suits your project's requirements and team's preferences, and enjoy the benefits of a well-structured CSS codebase.

Create a website that grows with you

Get Started