diff --git a/src/display/display_utils.js b/src/display/display_utils.js
index 0a9c5e4db..2d48082ad 100644
--- a/src/display/display_utils.js
+++ b/src/display/display_utils.js
@@ -992,7 +992,7 @@ function renderRichText({ html, dir, className }, container) {
       intent: "richText",
     });
   }
-  fragment.firstChild.classList.add("richText", className);
+  fragment.firstElementChild.classList.add("richText", className);
   container.append(fragment);
 }
 
diff --git a/src/display/draw_layer.js b/src/display/draw_layer.js
index 3c763f443..61994012a 100644
--- a/src/display/draw_layer.js
+++ b/src/display/draw_layer.js
@@ -208,8 +208,8 @@ class DrawLayer {
       }
     }
     if (path) {
-      const defs = element.firstChild;
-      const pathElement = defs.firstChild;
+      const defs = element.firstElementChild;
+      const pathElement = defs.firstElementChild;
       this.#updateProperties(pathElement, path);
     }
   }
diff --git a/src/display/editor/color_picker.js b/src/display/editor/color_picker.js
index 53dab57d2..e7561516b 100644
--- a/src/display/editor/color_picker.js
+++ b/src/display/editor/color_picker.js
@@ -183,7 +183,7 @@ class ColorPicker {
       return;
     }
     if (event.target === this.#button) {
-      this.#dropdown.firstChild?.focus();
+      this.#dropdown.firstElementChild?.focus();
       return;
     }
     event.target.nextSibling?.focus();
@@ -191,7 +191,7 @@ class ColorPicker {
 
   _moveToPrevious(event) {
     if (
-      event.target === this.#dropdown?.firstChild ||
+      event.target === this.#dropdown?.firstElementChild ||
       event.target === this.#button
     ) {
       if (this.#isDropdownVisible) {
@@ -210,7 +210,7 @@ class ColorPicker {
       this.#openDropdown(event);
       return;
     }
-    this.#dropdown.firstChild?.focus();
+    this.#dropdown.firstElementChild?.focus();
   }
 
   _moveToEnd(event) {
@@ -218,7 +218,7 @@ class ColorPicker {
       this.#openDropdown(event);
       return;
     }
-    this.#dropdown.lastChild?.focus();
+    this.#dropdown.lastElementChild?.focus();
   }
 
   #keyDown(event) {
diff --git a/src/display/editor/editor.js b/src/display/editor/editor.js
index 084fa34f1..043873e6d 100644
--- a/src/display/editor/editor.js
+++ b/src/display/editor/editor.js
@@ -2051,11 +2051,13 @@ class AnnotationEditor {
       // on the top-left one.
       if (nextFirstPosition < firstPosition) {
         for (let i = 0; i < firstPosition - nextFirstPosition; i++) {
-          this.#resizersDiv.append(this.#resizersDiv.firstChild);
+          this.#resizersDiv.append(this.#resizersDiv.firstElementChild);
         }
       } else if (nextFirstPosition > firstPosition) {
         for (let i = 0; i < nextFirstPosition - firstPosition; i++) {
-          this.#resizersDiv.firstChild.before(this.#resizersDiv.lastChild);
+          this.#resizersDiv.firstElementChild.before(
+            this.#resizersDiv.lastElementChild
+          );
         }
       }
 
@@ -2069,7 +2071,7 @@ class AnnotationEditor {
 
     this.#setResizerTabIndex(0);
     this.#isResizerEnabledForKeyboard = true;
-    this.#resizersDiv.firstChild.focus({ focusVisible: true });
+    this.#resizersDiv.firstElementChild.focus({ focusVisible: true });
     event.preventDefault();
     event.stopImmediatePropagation();
   }
@@ -2397,12 +2399,12 @@ class AnnotationEditor {
   }
 
   resetAnnotationElement(annotation) {
-    const { firstChild } = annotation.container;
+    const { firstElementChild } = annotation.container;
     if (
-      firstChild?.nodeName === "DIV" &&
-      firstChild.classList.contains("annotationContent")
+      firstElementChild?.nodeName === "DIV" &&
+      firstElementChild.classList.contains("annotationContent")
     ) {
-      firstChild.remove();
+      firstElementChild.remove();
     }
   }
 }
diff --git a/web/comment_manager.js b/web/comment_manager.js
index eaff727bd..98c6deae1 100644
--- a/web/comment_manager.js
+++ b/web/comment_manager.js
@@ -392,8 +392,8 @@ class CommentSidebar {
       return;
     }
 
-    this.#setDate(element.firstChild, modificationDate || creationDate);
-    this.#setText(element.lastChild, richText, contentsObj);
+    this.#setDate(element.firstElementChild, modificationDate || creationDate);
+    this.#setText(element.lastElementChild, richText, contentsObj);
 
     this.#annotations.splice(index, 1);
     index = binarySearchFirstItem(
diff --git a/web/new_alt_text_manager.js b/web/new_alt_text_manager.js
index d9554b779..546056f0b 100644
--- a/web/new_alt_text_manager.js
+++ b/web/new_alt_text_manager.js
@@ -444,7 +444,7 @@ class NewAltTextManager {
   }
 
   #close() {
-    const canvas = this.#imagePreview.firstChild;
+    const canvas = this.#imagePreview.firstElementChild;
     canvas.remove();
     canvas.width = canvas.height = 0;
     this.#imageData = null;
@@ -619,7 +619,7 @@ class ImageAltTextSettings {
   async #download(isFromUI = false) {
     if (isFromUI) {
       this.#downloadModelButton.disabled = true;
-      const span = this.#downloadModelButton.firstChild;
+      const span = this.#downloadModelButton.firstElementChild;
       span.setAttribute(
         "data-l10n-id",
         "pdfjs-editor-alt-text-settings-downloading-model-button"