Buffer CSS Style Guide

Goal

To establish more consistency and readability across the Buffer team and our open source projects.

Ideals

Have a bias toward clarity - from The Buffer Values

Table of Contents

1. Objects and Modifiers
2. Rule Declaration
3. Preprocessors

Objects and Modifiers

To write our CSS, we try and follow this simple naming convention:

Objects

Objects are standalone entities that are meaningful on their own. Objects that are made up of multiple words are connected by a single -.

Examples:

header, sidebar, button, icon, footer, footer-navigation

Modifiers

Modifiers change the appearance or behavior of objects. They are suffixed to the end of an object with a prefix of --.

Example:

button--disabled, icon--small, navigation--hidden

In Practice

HTML:

<button class="button">
  Filter
</button>

<button class="button button--primary">
  Add to Queue
</button>

<button class="button">
  <i class="icon button-icon icon-calendar"></i>
  Schedule
</button>

<button class="button button--primary">
  <i class="icon button-icon--primary icon-plus"></i>
  Add New Account
</button>

CSS:

/* Buttons
------------------------------------------------------------ */
.button {
  padding: 0 24px;
  height: 32px;

  font-size: 14px;
  line-height: 32px;
  color: #323b43;

  background-color: #ffffff;
  border: 1px solid #ced7df;
  border-radius: 4px;
}

.button--primary {
  color: #ffffff;

  background-color: #168eea;
  border-color: rgba(0, 0, 0, 0.2);
  border-radius: 32px;
}

.button-icon {
  @include Button-Icon-Margin

  color: #323b43;
}

.button-icon--primary {
  @include Button-Icon-Margin

  color: #ffffff;
}

/* Icons
------------------------------------------------------------ */
.icon {
  width: 16px;
  height: 16px;
}

Benefits

Modularity

Objects styles should not have dependencies on other elements on a page. This will reduce any problems from cascading. It'll also give us the ability to transfer objects from one area to another without the risk of breaking a page's structure.

Reusability

Composing independent objects in a different way and reusing them reduces the amount of CSS needed and also helps maintainability.

A goal that we're keen to focus on is to have a library of production-ready objects as part of our style guide that we can simply copy and paste in to our projects as we're building Buffer.

Structure

Buffer's OM methodology, inspired by BEM, gives us a simple and understandable structure in how we write our CSS.

General Formatting Rules

Indentation

We indent by 2 spaces at a time and try to avoid mixing tabs and spacing:

.button {
  color: #fff;
}

Lowercase

All of our CSS should be lower case:

.button--primary {
  color: #ffffff;

  background-color: #168eea;
  border-color: rgba(0, 0, 0, 0.2);
  border-radius: 32px;
}

Declaration Order

We use the box model coupled with a line space between each section:

.button {
  padding: 0 24px;
  height: 32px;

  font-size: 14px;
  line-height: 32px;
  color: #323b43;

  background-color: #ffffff;
  border: 1px solid #ced7df;
  border-radius: 4px;
}

Declaration Stops

We should end every declaration with a semicolon:

.button {
  background-color: #ffffff;
  border: 1px solid #ced7df;
  border-radius: 4px;
}

Property Name Stops

We use a single space between the property and value and no space between the property and the colon:

.button {
  height: 32px;
}

Declaration Block Separation

We use a single space between the last selector and the opening brace that begins the declaration block. The opening brace should be on the same line as the last selector in a given rule:

.button {
  // ...
}

Selector and Declaration Separation:

We start a new line for each selector and declaration:

h1,
h2,
h3 {
  font-weight: 600;
}

Rule Separation

We put a blank line between rules:

html {
  background: #f4f7f9;
}

body {
  font-size: 14px;
}

CSS Quotation Marks

We use single quotation marks for attribute selectors and property values. We try and omit quotation marks completely in URI values (url()):

@import url(//www.buffer.com/css/someCSSFile.css);

html {
  font-family: 'open sans', sans-serif;
}

Preprocessors

TODO