Is possible to assign a default class to the images that are part of a post content? I have a problem with teh layout, this because the attached images insetred inside a post will break my bootstrap layout. I want to assign a default class so the user when add an image into the content will have the class assigned and the layout will not break.

2 Answers 2


As you are using bootstrap you can add img-fluid helper class to images like this.

function example_add_img_class( $class ) {
    return $class . ' img-fluid';
add_filter( 'get_image_tag_class', 'example_add_img_class' );

get_image_tag_class filter allows to add custom css class along side WordPress default classes. Read more about the filter here


I guess you seeking of get_image_tag_class filter.

  • 3
    How it's an answer? Edit and add Code example. Jul 8, 2020 at 14:33

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