This is quite a starter question. I want to change the style of all the posts in the "photos" category by adding custom CSS to the style.css file of my child theme. However, I cannot find any category tags for my posts in the source code. Therefore I can not target it. So how can I add a "photos" class to all entries that fall under the Photos category?
I am using the TwentyTwentyTwo theme with a Child theme.

  • do you mean a css class? A tag would be <tag> which wouldn't make much sense. When you say you want to style all posts in the photos category are you talking about when they appear in a list/archive or are you talking about when you've clicked on a "photo" post and are viewing it? It's not clear
    – Tom J Nowell
    Commented Apr 5, 2023 at 13:34
  • Thanks @TomJNowell for the questions. Sorry I wasn't clear. So yes, I was looking for a css class. To clarify: I have a website and on that site among different pages (Home, Contact, etc.) there is a page named Photos. That Photos page has links to 3 or more posts. These posts all have the category "photos". I'm looking for a way to be able to change the style of these posts, to avoid doing it one-by-one (eg. targeting the postid-) for each because it's not so efficient. That is why I thought there might be a way of getting a class for all the posts which are under the "photos" category.
    – Klosmi
    Commented Apr 5, 2023 at 14:24
  • I'm still unclear, e.g. if you wanted to target the class to add outline:1px solid hotpink;would it be the links on the photos page that are outlined? Or the content when you click on that link? Or the photos page itself? I understand that you have posts, but it's not clear which part specifically you want to style. A screenshot with an arrow would help enormously as your description never specifies the specific thing you want to style explicitly, only indirectly
    – Tom J Nowell
    Commented Apr 5, 2023 at 14:39
  • if it's the posts themselves once you've clicked on the link, then you should be able to target css class names that are added by WordPress to the body tag to build a CSS selector
    – Tom J Nowell
    Commented Apr 5, 2023 at 14:40
  • Sorry again for being unclear. I provided 2 images (see in the question above). The 1st is the website on the Photos page, in the middle 2 buttons. By clicking on the 1st one it directs to the Concert photos post (the 2nd image). The 2nd button goes to the Theater co-productions post. If I want to change eg. the background to blue color for all the posts I have related to the Photos page, I couldn't find the way to do that. For specific post indeed I can do that by using the ID in the body tag, like #postid-412. But for the other post I have to use another id, for newer posts do it again.
    – Klosmi
    Commented Apr 5, 2023 at 15:49

1 Answer 1


I managed to solve my problem.
So, the posts are using a single.html template file (in the TwenytTwentyTwo theme: /templates/single.html).
I wanted to target a category class in the <body> element of the single.html. To make that happen, I had to modify the single.html file in my Child theme by adding the following code snippet within the main wp:group block:

<!-- wp:post-terms {"term":"category"} /-->

After that, in the functions.php I added a function that adds a category class to the post's HTML <body> element on the single post pages.
(I added comments to make it clear.)

// Get posts category 
function add_category_class( $classes ) {

  // Check if the current page being viewed is a single post
  if ( is_single() ) {

  // The $post variable is set to the current post being viewed
    global $post;

  // Loop through each category of the post, add a class "category-" to the $classes array 
  // Followed by the category's slug (URL-friendly)
  // Each category associated with the current post, and the "get_the_category( $post->ID )" function is getting those categories based on the ID of the current post.
    foreach ( ( get_the_category( $post->ID ) ) as $category ) {
      $classes[] = 'category-' . $category->slug;

 // Return the updated body classes array
  return $classes;

// Add the classes to the body tag of the post
add_filter( 'body_class', 'add_category_class' );

and in the style.css I was able to target it (here the photos category is selected).

   /* Change background color for posts in Photos category */    
    .category-photos { 
      background-color: red; 

That made the background red of a single post page within a a specific category.

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