How can I override inline styles with external CSS?

Question

The only way to override inline style is by using !important keyword beside the CSS rule. The following is an example of it.

div {
        color: blue !important;
       /* Adding !important will give this rule more precedence over inline style */
    }

<div style="font-size: 18px; color: red;">
    Hello, World. How can I change this to blue?
</div>

Important Notes:

• Using !important is not considered as a good practice. Hence, you should avoid both !important and inline style.

• Adding the !important keyword to any CSS rule lets the rule forcefully precede over all the other CSS rules for that element.

• It even overrides the inline styles from the markup.

• The only way to override is by using another !important rule, declared either with higher CSS specificity in the CSS, or equal CSS specificity later in the code.

• Must Read - CSS Specificity by MDN 🔗

inline-styles in a document have the highest priority, so for example say if you want to change the color of a div element to blue, but you've an inline style with a color property set to red

<div style="font-size: 18px; color: red;">
   Hello World, How Can I Change The Color To Blue?
</div>

div {
   color: blue; 
   /* This Won't Work, As Inline Styles Have Color Red And As 
      Inline Styles Have Highest Priority, We Cannot Over Ride 
      The Color Using An Element Selector */
}

So, Should I Use jQuery/Javascript? - Answer Is NO

We can use element-attr CSS Selector with !important, note, !important is important here, else it won't over ride the inline styles..

<div style="font-size: 30px; color: red;">
    This is a test to see whether the inline styles can be over ridden with CSS?
</div>

div[style] {
   font-size: 12px !important;
   color: blue !important;
}

Demo

Note: Using !important ONLY will work here, but I've used div[style] selector to specifically select div having style attribute

You can easily override inline style except inline !important style

so

<div style="font-size: 18px; color: red;">
    Hello World, How Can I Change The Color To Blue?
</div>

div {
   color: blue !important; 
   /* This will  Work */
}

but if you have

<div style="font-size: 18px; color: red !important;">
    Hello World, How Can I Change The Color To Blue?
</div>

div {
   color: blue !important; 
   /* This Isn't Working */
}

now it will be red only .. and you can not override it

<div style="background: red;">
    The inline styles for this div should make it red.
</div>

div[style] {
   background: yellow !important;
}

Below is the link for more details: http://css-tricks.com/override-inline-styles-with-css/