How to make addEventListener affect multiple divs [duplicate]

I am new to code, so please don’t be too harsh on me. I am using this code to create a button that would store and load edited data from localStorage, and make divs with the class “content” editable. Whenever I click the button, however, it only makes the first div editable. Is there a way to make it apply to all divs with the class “content”?

window.onload = function() {
    if(localStorage.getItem('content')) {
        document.querySelector('.content').innerHTML = localStorage.getItem('content');
  }
}

let editBtn = document.querySelector('#edit_content');
let content = document.querySelector('.content');

editBtn.addEventListener('click', () => {
    content.contentEditable = !content.isContentEditable;
  if(content.contentEditable === 'false') {
    localStorage.setItem('content', content.innerHTML);
  }
});

I tried using querySelectorAll(), but that just made the button not work at all.