Outer Glow (Box Elements)

In CSS, you can create both inner and outer glow effects using the box-shadow and text-shadow properties. The key to creating a glow (rather than a sharp shadow) is using a large blur radius with zero offsets. 

Outer Glow (Box Elements)

Use the box-shadow property without the inset keyword. Multiple shadows can be stacked for a more intense or multi-color effect. 

  • Syntaxbox-shadow: [horizontal-offset] [vertical-offset] [blur-radius] [spread-radius] [color];
  • For an even glow around all sides, set the horizontal and vertical offsets to 0

Example (Outer Glow):

css

.outer-glow {
  /* 0 0 means no x or y offset, 15px is the blur, 5px is the spread, #ff00ff is the color */
  box-shadow: 0 0 15px 5px #ff00ff;
  /* Stacking multiple shadows for a stronger glow */
  box-shadow: 0 0 10px #fff, 0 0 20px #ff00ff, 0 0 30px #ff00ff;
}

Inner Glow (Box Elements)

Use the box-shadow property with the inset keyword. This makes the shadow appear inside the element’s border. 

  • Syntaxbox-shadow: inset [horizontal-offset] [vertical-offset] [blur-radius] [spread-radius] [color]; 

Example (Inner Glow):

css

.inner-glow {
  /* Inset creates an inner shadow */
  box-shadow: inset 0 0 15px 5px #00ffff;
  background-color: #333; /* A dark background helps the glow stand out */
}

Outer Glow (Text)

Use the text-shadow property to apply a glow effect to text. 

  • Syntaxtext-shadow: [horizontal-offset] [vertical-offset] [blur-radius] [color];
  • Like box-shadow, set offsets to 0 for an even glow. 

Example (Text Glow):

css

.text-glow {
  color: white;
  /* Multiple shadows can be used here too */
  text-shadow: 0 0 5px #fff, 0 0 10px #0fa, 0 0 15px #0fa;
}

Inner Glow (Text)

An inner glow effect for text is trickier to achieve purely with simple CSS properties. A common method involves a combination of text-stroke (using the -webkit-text-stroke prefix for compatibility) and text-shadow

Example (Inner Text Border/Glow effect):

css

.inner-text-glow {
  color: purple; /* The inner color of the text */
  -webkit-text-stroke: 1px white; /* The "inner glow" border */
  text-shadow: 0 0 10px red; /* The outer glow */
}

You can experiment with different values and combinations of these properties to achieve the desired visual effects, and use tools like a Box Shadow CSS Generator to assist in generating the CSS code.