diff --git a/assets/js/handlers.js b/assets/js/handlers.js
index 67cd9081..d765a48f 100644
--- a/assets/js/handlers.js
+++ b/assets/js/handlers.js
@@ -146,4 +146,15 @@
             event.preventDefault();
         }
     });
+
+    // Handle the video watched state with JavaScript (if enabled)
+    const anchorElements = document.querySelectorAll('a[href^="/watch"]');
+
+    for (const anchorElement of anchorElements) {
+        const url = new URL(anchorElement.href);
+
+        url.searchParams.set("mark_watched", "0");
+        
+        anchorElement.href = url.href;
+    }
 })();
diff --git a/assets/js/player.js b/assets/js/player.js
index ecdc0448..c4a76167 100644
--- a/assets/js/player.js
+++ b/assets/js/player.js
@@ -126,13 +126,37 @@ function addCurrentTimeToURL(url, base) {
  */
 var timeupdate_last_ts = 5;
 
+/** 
+ * Global variable to save the total video time watched (in seconds).
+ */
+let time_watched = 0;
+
 /**
- * Callback that updates the timestamp on all external links
+ * The duration of a short video (in seconds).
+ * This value is used to determine whether the video should be watched fully before
+ * being marked as watched.
+ * 
+ * @default 30
+ */
+const SHORT_VIDEO_DURATION = 30;
+
+/**
+ * The duration (in seconds) after which a video should be marked as watched.
+ * 
+ * @default 30
+ */
+const MARK_WATCHED_AFTER_DURATION = SHORT_VIDEO_DURATION;
+
+/**
+ * Callback that updates the timestamp on all external links and marks the video as watched after:
+ * - fully watching short videos (<=30 seconds)
+ * - time watched reaches 30 seconds for long videos (>30 seconds)
  */
 player.on('timeupdate', function () {
     // Only update once every second
     let current_ts = Math.floor(player.currentTime());
-    if (current_ts > timeupdate_last_ts) timeupdate_last_ts = current_ts;
+    const last_player_time = timeupdate_last_ts;
+    if (current_ts !== timeupdate_last_ts) timeupdate_last_ts = current_ts;
     else return;
 
     // YouTube links
@@ -166,6 +190,49 @@ player.on('timeupdate', function () {
         let base_url_iv_other = elem_iv_other.getAttribute('data-base-url');
         elem_iv_other.href = addCurrentTimeToURL(base_url_iv_other, domain);
     }
+
+    // Only increase time watched when the time difference is one second and the video has not been marked as watched
+    const isOneSecondDifference = current_ts - last_player_time === 1;
+    const exceedsMarkWatchedAfterDuration = time_watched > MARK_WATCHED_AFTER_DURATION;
+
+    if (!isOneSecondDifference || exceedsMarkWatchedAfterDuration) return;
+    
+    time_watched += 1;
+
+    // Check if time watched exceeds 30 seconds or the video is fully watched
+    const absolute_video_duration = Math.floor(player.duration());
+    const watched_at_timestamp = absolute_video_duration > SHORT_VIDEO_DURATION
+        ? MARK_WATCHED_AFTER_DURATION
+        : absolute_video_duration;
+
+    if (time_watched !== watched_at_timestamp) return;
+
+    const video_id = document.querySelector('[name="id"]').value;
+    const $csrfToken = document.querySelector('[name="csrf_token"]');
+
+    // User is not logged in
+    if ($csrfToken === null) return;
+
+    // Mark the video as watched
+    const csrf_token = $csrfToken.value;
+
+    const params = new URLSearchParams({
+        action: "mark_watched",
+        redirect: false,
+        id: video_id
+    });
+
+    const url = `/watch_ajax?${params}`;
+
+    helpers.xhr('POST', url, { payload: `csrf_token=${csrf_token}` }, {
+        on200: () => {
+            console.info(`Marked video ${video_id} as watched`);
+        },
+        onNon200: ({ response }) => {
+            console.error(`Something went wrong while marking video ${video_id} as watched:`, response);
+        }
+    });
+
 });
 
 
diff --git a/src/invidious/routes/watch.cr b/src/invidious/routes/watch.cr
index 4c181503..475f68a9 100644
--- a/src/invidious/routes/watch.cr
+++ b/src/invidious/routes/watch.cr
@@ -67,7 +67,7 @@ module Invidious::Routes::Watch
     end
     env.params.query.delete_all("iv_load_policy")
 
-    if watched && preferences.watch_history
+    if watched && (env.params.query["mark_watched"]? || "1") == "1"
       Invidious::Database::Users.mark_watched(user.as(User), id)
     end