How to make an element's background-color a little darker using CSS

Question

I have the following CSS for a button:

.Button {
  background-color: #somehex;
}

When the user hovers over the button, I want the background-color to be a little darker. I have tried changing opacity, which didn't work, and currently am doing it this way:

.Button:hover {
  transition: 0.2s ease-in;
  background-color: #ALittleDarkerHex;
}

While this process works, it is really tedious because I have to manually look for a darker version of the color I am working with. I was wondering if there was an easier way to darken the background-color of a button using CSS.

Answer 1

Add a dark layer on the top of it using background-image. This method keeps your text visible in the same color while changing only the background.

.button {
  display: inline-block;
  color:#fff;
  padding: 10px 20px;
  font-size: 20px;
  background-color:red;
}

.button:hover {
  background-image: linear-gradient(rgba(0, 0, 0, 0.4) 0 0);
}

<div class="button"> some text </div>
<div class="button" style="background-color:lightblue;"> some text </div>
<div class="button" style="background-color:green;"> some text </div>
<div class="button" style="background-color:grey;"> some text </div>

To have a transition:

.button {
  display: inline-block;
  color:#fff;
  padding: 10px 20px;
  font-size: 20px;
  background: linear-gradient(transparent,rgba(0, 0, 0, 0.4)) top/100% 800%;
  background-color:red;
  transition:0.5s;
}

.button:hover {
  background-position:bottom;
}

<div class="button"> some text </div>
<div class="button" style="background-color:lightblue;"> some text </div>
<div class="button" style="background-color:green;"> some text </div>
<div class="button" style="background-color:grey;"> some text </div>

Another idea with mix-blend-mode:

.button {
  display: inline-block;
  color: #fff;
  padding: 10px 20px;
  font-size: 20px;
  background-color: red;
  background-image: linear-gradient(rgba(0, 0, 0, 0.4) 0 0);
  background-blend-mode: lighten;
}

.button:hover {
  background-blend-mode: darken;
}

<div class="button"> some text </div>
<div class="button" style="background-color:lightblue;"> some text </div>
<div class="button" style="background-color:green;"> some text </div>
<div class="button" style="background-color:grey;"> some text </div>

Answer 2

This is one way you can do it

.button {
  background-color: red;
}

.button:hover {
    filter: brightness(60%);
}

<button class="button">Button</button>

Anything above brightness(100%) will increase the brightness and anything less will make it darker.