diff --git a/bulkredditdownloader/__main__.py b/bulkredditdownloader/__main__.py
index d8d1f08..8a48958 100644
--- a/bulkredditdownloader/__main__.py
+++ b/bulkredditdownloader/__main__.py
@@ -39,6 +39,7 @@ def cli():
 @click.option('--set-folder-scheme', default=None, type=str)
 @click.option('--no-dupes', is_flag=True, default=None)
 @click.option('--config', type=str, default=None)
+@click.option('--search-existing', is_flag=True, default=None)
 @click.pass_context
 def cli_download(context: click.Context, **_):
     config = Configuration()
diff --git a/bulkredditdownloader/configuration.py b/bulkredditdownloader/configuration.py
index a467cd1..6633ec2 100644
--- a/bulkredditdownloader/configuration.py
+++ b/bulkredditdownloader/configuration.py
@@ -19,6 +19,7 @@ class Configuration(Namespace):
         self.no_dupes: bool = False
         self.saved: bool = False
         self.search: Optional[str] = None
+        self.search_existing: bool = False
         self.set_file_scheme: str = '{REDDITOR}_{TITLE}_{POSTID}'
         self.set_folder_scheme: str = '{SUBREDDIT}'
         self.skip: list[str] = []
diff --git a/bulkredditdownloader/downloader.py b/bulkredditdownloader/downloader.py
index 5b939b0..d8eb54d 100644
--- a/bulkredditdownloader/downloader.py
+++ b/bulkredditdownloader/downloader.py
@@ -2,7 +2,9 @@
 # coding=utf-8
 
 import configparser
+import hashlib
 import logging
+import os
 import re
 import socket
 from datetime import datetime
@@ -116,7 +118,7 @@ class RedditDownloader:
         return master_list
 
     def _determine_directories(self):
-        self.download_directory = Path(self.args.directory)
+        self.download_directory = Path(self.args.directory).resolve().expanduser()
         self.logfile_directory = self.download_directory / 'LOG_FILES'
         self.config_directory = self.config_directories.user_config_dir
 
@@ -313,3 +315,15 @@ class RedditDownloader:
                         self.master_hash_list.append(res.hash.hexdigest())
                         logger.debug(f'Hash added to master list: {res.hash.hexdigest()}')
                         logger.info(f'Downloaded submission {submission.name}')
+
+    def scan_existing_files(self) -> list[str]:
+        files = []
+        for (dirpath, dirnames, filenames) in os.walk(self.download_directory):
+            files.extend([Path(dirpath, file) for file in filenames])
+        logger.info(f'Calculating hashes for {len(files)} files')
+        hash_list = []
+        for existing_file in files:
+            with open(existing_file, 'rb') as file:
+                hash_list.append(hashlib.md5(file.read()).hexdigest())
+                logger.log(9, f'Hash calculated for file at {existing_file}')
+        return hash_list
diff --git a/bulkredditdownloader/tests/test_downloader.py b/bulkredditdownloader/tests/test_downloader.py
index 2c4208f..dc7c427 100644
--- a/bulkredditdownloader/tests/test_downloader.py
+++ b/bulkredditdownloader/tests/test_downloader.py
@@ -407,3 +407,10 @@ def test_download_submission_hash_exists(
 def test_sanitise_subreddit_name(test_name: str, expected: str):
     result = RedditDownloader._sanitise_subreddit_name(test_name)
     assert result == expected
+
+
+def test_search_existing_files(downloader_mock: MagicMock):
+    downloader_mock.download_directory = Path('.').resolve().expanduser()
+    results = RedditDownloader.scan_existing_files(downloader_mock)
+    assert all([isinstance(result, str) for result in results])
+    assert len(results) >= 40