Get rid of white space around Angular Material modal dialog

Question

Updated Answer

From the official documentation:

Styling overlay components

Overlay-based components have a panelClass
property (or similar) that can be used to target the overlay pane.

You can override the default dialog container styles by adding a css class in your global styles.css. For example:

.custom-dialog-container .mat-dialog-container {
    /* add your styles */
}

After that, you’ll need to providies you css class as a panelClass parameter to your dialog:

this.dialog.open(MyDialogComponent, { panelClass: 'custom-dialog-container' })

Link to StackBlitz Demo. Read this official documentation for more information.

Original Answer

Use ViewEncapsulation to override default styles with your styles.

In the component which opens the dialog, do the following changes:

import {ViewEncapsulation} from '@angular/core';
    
@Component({
  .....,
  encapsulation: ViewEncapsulation.None 
})

and in that component’s css file, add the following class:

.mat-dialog-container {
    padding: 0px !important;
}

Here is a link to Plunker Demo.