diff --git a/package.json b/package.json
index aa2fde99..5b61c1bd 100644
--- a/package.json
+++ b/package.json
@@ -56,7 +56,7 @@
     "playwright": "^1.55.1",
     "prettier": "^3.6.2",
     "sinon": "^19.0.2",
-    "typescript": "^5.6.3",
+    "typescript": "^6.0.3",
     "typescript-eslint": "^8.53.1",
     "vitest": "^4.1.7"
   },
diff --git a/via/static/scripts/types/css-custom-highlights.d.ts b/via/static/scripts/types/css-custom-highlights.d.ts
deleted file mode 100644
index ba5cbaec..00000000
--- a/via/static/scripts/types/css-custom-highlights.d.ts
+++ /dev/null
@@ -1,16 +0,0 @@
-// Types for the CSS Custom Highlight API.
-//
-// See https://developer.mozilla.org/en-US/docs/Web/API/CSS_Custom_Highlight_API.
-//
-// TypeScript's built-in types includes incomplete versions of these types.
-
-declare interface Highlight {
-  add(r: Range): void;
-  delete(r: Range): void;
-}
-
-interface HighlightRegistry {
-  delete(name: string): void;
-  get(name: string): Highlight | undefined;
-  set(name: string, highlight: Highlight): void;
-}
diff --git a/via/static/scripts/video_player/utils/youtube.ts b/via/static/scripts/video_player/utils/youtube.ts
index d1ef4368..15e1904c 100644
--- a/via/static/scripts/video_player/utils/youtube.ts
+++ b/via/static/scripts/video_player/utils/youtube.ts
@@ -1,3 +1,5 @@
+/// <reference types="youtube" />
+
 /**
  * Load the YouTube IFrame Player API.
  *
diff --git a/yarn.lock b/yarn.lock
index ae924a71..07f4f999 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -9247,23 +9247,23 @@ __metadata:
   languageName: node
   linkType: hard
 
-"typescript@npm:^5.6.3":
-  version: 5.6.3
-  resolution: "typescript@npm:5.6.3"
+"typescript@npm:^6.0.3":
+  version: 6.0.3
+  resolution: "typescript@npm:6.0.3"
   bin:
     tsc: bin/tsc
     tsserver: bin/tsserver
-  checksum: ba302f8822777ebefb28b554105f3e074466b671e7444ec6b75dadc008a62f46f373d9e57ceced1c433756d06c8b7dc569a7eefdf3a9573122a49205ff99021a
+  checksum: c1182dfadf8a8cb22a4e32442715afef1af1b950ae635b1c52c27e0d7fb7a5e2607ed7c7c4079bba4163579250e02445fd8d46b09cbceda71ff72a5b7d69db61
   languageName: node
   linkType: hard
 
-"typescript@patch:typescript@^5.6.3#~builtin<compat/typescript>":
-  version: 5.6.3
-  resolution: "typescript@patch:typescript@npm%3A5.6.3#~builtin<compat/typescript>::version=5.6.3&hash=14eedb"
+"typescript@patch:typescript@^6.0.3#~builtin<compat/typescript>":
+  version: 6.0.3
+  resolution: "typescript@patch:typescript@npm%3A6.0.3#~builtin<compat/typescript>::version=6.0.3&hash=14eedb"
   bin:
     tsc: bin/tsc
     tsserver: bin/tsserver
-  checksum: ade87bce2363ee963eed0e4ca8a312ea02c81873ebd53609bc3f6dc0a57f6e61ad7e3fb8cbb7f7ab8b5081cbee801b023f7c4823ee70b1c447eae050e6c7622b
+  checksum: 8ed159a81ab4901a620c19fda539632cee610f8ec34dde57a3acc6b6df72894ad0b50bdd1946b763313d9b73dedb019d2e81c03eff06c0f2c785cde30a537d15
   languageName: node
   linkType: hard
 
@@ -9458,7 +9458,7 @@ __metadata:
     sinon: ^19.0.2
     tailwindcss: ^4.1.17
     terser: ^5.39.0
-    typescript: ^5.6.3
+    typescript: ^6.0.3
     typescript-eslint: ^8.53.1
     vitest: ^4.1.7
   languageName: unknown