WordPress has trouble with the width and height attributes for SVGs. The width and height attributes can be removed for SVGs using this code adapted from trac ticket #26256 .
/**
* Removes the width and height attributes of <img> tags for SVG
*
* Without this filter, the width and height are set to "1" since
* WordPress core can't seem to figure out an SVG file's dimensions.
*
* For SVG:s, returns an array with file url, width and height set
* to null, and false for 'is_intermediate'.
*
* @wp-hook image_downsize
* @param mixed $out Value to be filtered
* @param int $id Attachment ID for image.
* @return bool|array False if not in admin or not SVG. Array otherwise.
*/
function wpse240579_fix_svg_size_attributes( $out, $id ) {
$image_url = wp_get_attachment_url( $id );
$file_ext = pathinfo( $image_url, PATHINFO_EXTENSION );
if ( is_admin() || 'svg' !== $file_ext ) {
return false;
}
return array( $image_url, null, null, false );
}
add_filter( 'image_downsize', 'wpse240579_fix_svg_size_attributes', 10, 2 );