diff --git a/s3_bucket_downloader/src/main.rs b/s3_bucket_downloader/src/main.rs
index 402542b..f5e1328 100644
--- a/s3_bucket_downloader/src/main.rs
+++ b/s3_bucket_downloader/src/main.rs
@@ -59,6 +59,10 @@ struct Args {
     /// File containing list of files to download (one per line)
     #[arg(short, long)]
     file_list: Option<String>,
+
+    /// Redownload mode: check existing files and only download missing ones
+    #[arg(short = 'd', long, default_value_t = false)]
+    redownload: bool,
 }
 
 #[tokio::main]
@@ -69,6 +73,7 @@ async fn main() {
     let local_dir = PathBuf::from(args.output);
     let num_workers = args.workers;
     let max_retries = args.retries;
+    let redownload = args.redownload;
 
     if !local_dir.exists() {
         fs::create_dir_all(&local_dir).expect("Failed to create output directory");
@@ -111,11 +116,34 @@ async fn main() {
         keys
     };
 
-    println!(
-        "Found {} files. Starting downloads with {} threads...",
-        keys.len(),
-        num_workers
-    );
+    // Filter out existing files in redownload mode
+    let keys_to_download = if redownload {
+        let mut missing_keys = Vec::new();
+        let mut existing_count = 0;
+        for key in &keys {
+            let local_path = local_dir.join(key);
+            if local_path.exists() {
+                existing_count += 1;
+            } else {
+                missing_keys.push(key.clone());
+            }
+        }
+        println!(
+            "Found {} existing files, {} files to download",
+            existing_count,
+            missing_keys.len()
+        );
+        missing_keys
+    } else {
+        keys
+    };
+
+    if keys_to_download.is_empty() {
+        println!("No files to download.");
+        return;
+    }
+
+    println!("Starting downloads with {} threads...", num_workers);
     rayon::ThreadPoolBuilder::new()
         .num_threads(num_workers)
         .build_global()
@@ -127,7 +155,7 @@ async fn main() {
     let downloaded_size = Arc::new(AtomicUsize::new(0));
 
     // Create overall progress bar
-    let total_pb = m.add(ProgressBar::new(keys.len() as u64));
+    let total_pb = m.add(ProgressBar::new(keys_to_download.len() as u64));
     total_pb.set_style(
         ProgressStyle::with_template(
             "{spinner} [{elapsed_precise}] [{bar:40.cyan/blue}] {pos}/{len} ({percent}%) {msg}",
@@ -136,7 +164,7 @@ async fn main() {
     );
 
     // Calculate files per thread
-    let files_per_thread = keys.len().div_ceil(num_workers);
+    let files_per_thread = keys_to_download.len().div_ceil(num_workers);
 
     // Create fixed progress bars for each thread
     let thread_pbs: Vec<_> = (0..num_workers)
@@ -151,54 +179,52 @@ async fn main() {
         })
         .collect();
 
-    keys.par_iter().enumerate().for_each(|(i, key)| {
-        let client = Arc::clone(&client);
-        let bucket = bucket_name.clone();
-        let dir = local_dir.clone();
-        let key = key.clone();
-        let downloaded = Arc::clone(&downloaded);
-        let failed = Arc::clone(&failed);
-        let downloaded_size = Arc::clone(&downloaded_size);
-        let total_pb = total_pb.clone();
-        let thread_num = i % num_workers;
-        let thread_pb = thread_pbs[thread_num].clone();
-
-        let rt = Runtime::new().unwrap();
-        rt.block_on(async move {
-            let local_path = dir.join(&key);
-            if let Some(parent) = local_path.parent() {
-                fs::create_dir_all(parent).expect("Failed to create parent directory");
-            }
-
-            match download_object_with_retry(&client, &bucket, &key, max_retries).await {
-                Ok(bytes) => {
-                    let mut file = File::create(&local_path).expect("Failed to create file");
-                    file.write_all(&bytes).expect("Failed to write file");
-                    downloaded.fetch_add(1, Ordering::SeqCst);
-                    downloaded_size.fetch_add(bytes.len(), Ordering::SeqCst);
-                    total_pb.inc(1);
-                    thread_pb.inc(1);
-                    thread_pb.set_message(format!(
-                        "Thread {}: Downloaded {}/{} files",
-                        thread_num + 1,
-                        downloaded.load(Ordering::SeqCst),
-                        files_per_thread
-                    ));
+    keys_to_download
+        .par_iter()
+        .enumerate()
+        .for_each(|(i, key)| {
+            let client = Arc::clone(&client);
+            let bucket = bucket_name.clone();
+            let dir = local_dir.clone();
+            let key = key.clone();
+            let downloaded = Arc::clone(&downloaded);
+            let failed = Arc::clone(&failed);
+            let downloaded_size = Arc::clone(&downloaded_size);
+            let total_pb = total_pb.clone();
+            let thread_num = i % num_workers;
+            let thread_pb = thread_pbs[thread_num].clone();
+
+            let rt = Runtime::new().unwrap();
+            rt.block_on(async move {
+                let local_path = dir.join(&key);
+                if let Some(parent) = local_path.parent() {
+                    fs::create_dir_all(parent).expect("Failed to create parent directory");
                 }
-                Err(_e) => {
-                    failed.fetch_add(1, Ordering::SeqCst);
-                    total_pb.inc(1);
-                    thread_pb.inc(1);
-                    thread_pb.set_message(format!(
-                        "Thread {}: Failed {}/{} files",
-                        thread_num + 1,
-                        failed.load(Ordering::SeqCst),
-                        files_per_thread
-                    ));
+
+                match download_object_with_retry(&client, &bucket, &key, max_retries).await {
+                    Ok(bytes) => {
+                        let mut file = File::create(&local_path).expect("Failed to create file");
+                        file.write_all(&bytes).expect("Failed to write file");
+                        downloaded.fetch_add(1, Ordering::SeqCst);
+                        downloaded_size.fetch_add(bytes.len(), Ordering::SeqCst);
+                        total_pb.inc(1);
+                        thread_pb.inc(1);
+                        thread_pb.set_message(format!("by Thread {}", thread_num + 1));
+                    }
+                    Err(_e) => {
+                        failed.fetch_add(1, Ordering::SeqCst);
+                        total_pb.inc(1);
+                        thread_pb.inc(1);
+                        thread_pb.set_message(format!(
+                            "Thread {}: Failed {}/{} files",
+                            thread_num + 1,
+                            failed.load(Ordering::SeqCst),
+                            files_per_thread
+                        ));
+                    }
                 }
-            }
+            });
         });
-    });
 
     // Clean up all progress bars
     for pb in thread_pbs {