diff --git a/crates/lib/url_utils/src/download_extension/extract_download_extension_from_url.rs b/crates/lib/url_utils/src/download_extension/extract_download_extension_from_url.rs
--- a/crates/lib/url_utils/src/download_extension/extract_download_extension_from_url.rs
+++ b/crates/lib/url_utils/src/download_extension/extract_download_extension_from_url.rs
@@ -1,4 +1,5 @@
 use crate::download_extension::DownloadExtension;
+use crate::extension::extract_extension_from_url::{extract_extension_from_url, ExtractExtensions};
 use url::Url;
 
 /// This should be used for naming files on the local file system based on their URL.
@@ -11,11 +12,8 @@ pub fn extract_download_extension_from_url_str(url: &str) -> Option<DownloadExte
 /// This should be used for naming files on the local file system based on their URL.
 #[deprecated(note = "Use `extract_extension_from_url` in `url_utils::extension::extract_extension_from_url` instead")]
 pub fn extract_download_extension_from_url(url: &Url) -> Option<DownloadExtension> {
-  let path = url.path();
-  let extension = std::path::Path::new(path)
-      .extension()
-      .and_then(|ext| ext.to_str())?;
-  DownloadExtension::try_from_str(extension)
+  let extension = extract_extension_from_url(url, &ExtractExtensions::All)?;
+  DownloadExtension::try_from_str(extension.without_period())
 }
 
 #[cfg(test)]
@@ -30,6 +28,42 @@ mod tests {
     assert_eq!(maybe_extension, Some(DownloadExtension::Jpg));
   }
 
+  mod final_path_segment {
+    use super::*;
+
+    #[test]
+    fn directory_path_does_not_infer_an_extension() {
+      assert_eq!(
+        extract_download_extension_from_url_str("https://example.com/assets.png/"),
+        None,
+      );
+    }
+
+    #[test]
+    fn opaque_url_does_not_infer_an_extension() {
+      assert_eq!(
+        extract_download_extension_from_url_str("data:text/plain,file.png"),
+        None,
+      );
+    }
+
+    #[test]
+    fn mixed_case_supported_filename_with_query_is_preserved() {
+      assert_eq!(
+        extract_download_extension_from_url_str("https://example.com/clip.MP4?token=abc"),
+        Some(DownloadExtension::Mp4),
+      );
+    }
+
+    #[test]
+    fn unknown_extension_remains_rejected() {
+      assert_eq!(
+        extract_download_extension_from_url_str("https://example.com/file.xyz"),
+        None,
+      );
+    }
+  }
+
   #[test]
   fn difficult_url() {
     let url = "https://videos.youtube.com/foo/bar/files/00000000-f19a-1275-a092-caa60b38f8d2%2Fraw?se=2025-11-21T22%3A26%3A53Z&sp=r&sv=2024-08-09&sr=b&skoid=8cfff87a-01fc-27c1-9091-32999dcd1389&sktid=aa8ccaf6-e6da-484e-ab11-9c7496c21c53&skt=2025-11-17T21%3A09%3A08Z&ske=2025-10-23T21%3A14%3A08Z&sks=b&skv=2024-08-04&sig=T2U6%2Brw9WJdJagBkCL4/GlFr72KhZGP3QPlobIO7JlU%3D&ac=oaisdsorprnorthcentralus";
diff --git a/crates/lib/url_utils/src/extension/extract_extension_from_url.rs b/crates/lib/url_utils/src/extension/extract_extension_from_url.rs
--- a/crates/lib/url_utils/src/extension/extract_extension_from_url.rs
+++ b/crates/lib/url_utils/src/extension/extract_extension_from_url.rs
@@ -61,10 +61,11 @@ pub fn extract_extension_from_url_str(url: &str, accept: &ExtractExtensions) ->
 
 /// Extracts a file extension from a parsed `Url`, filtered by `accept`.
 pub fn extract_extension_from_url(url: &Url, accept: &ExtractExtensions) -> Option<Extension> {
-  let path = url.path();
-  let raw_ext = std::path::Path::new(path)
+  let filename = url.path_segments()?.next_back()?;
+  let raw_ext = std::path::Path::new(filename)
     .extension()
-    .and_then(|ext| ext.to_str())?;
+    .and_then(|ext| ext.to_str())
+    .filter(|ext| !ext.is_empty())?;
 
   let lower = raw_ext.to_lowercase();
   let candidate = Extension::new(&lower);
@@ -104,6 +105,47 @@ fn slice_contains(extensions: &[Extension], candidate: &Extension) -> bool {
 mod tests {
   use super::*;
 
+  mod final_path_segment {
+    use super::*;
+
+    #[test]
+    fn directory_url_has_no_file_extension() {
+      for accept in [ExtractExtensions::All, ExtractExtensions::KnownImage] {
+        let ext = extract_extension_from_url_str("https://example.com/assets.png/", &accept);
+        assert_eq!(ext.map(|ext| ext.without_period().to_string()), None);
+      }
+    }
+
+    #[test]
+    fn empty_extension_is_not_a_filename_suffix() {
+      let ext = extract_extension_from_url_str(
+        "https://example.com/image.", &ExtractExtensions::All,
+      );
+      assert_eq!(ext.map(|ext| ext.without_period().to_string()), None);
+    }
+
+    #[test]
+    fn opaque_url_is_not_a_file_path() {
+      let ext = extract_extension_from_url_str(
+        "data:application/example.png", &ExtractExtensions::All,
+      );
+      assert_eq!(ext.map(|ext| ext.without_period().to_string()), None);
+    }
+
+    #[test]
+    fn parent_directory_extension_does_not_replace_the_file_extension() {
+      let ext = extract_extension_from_url_str(
+        "https://example.com/assets.png/reference.MP4?sig=value#preview",
+        &ExtractExtensions::KnownVideo,
+      );
+      assert_eq!(ext.unwrap().without_period(), "mp4");
+      let ext = extract_extension_from_url_str(
+        "https://example.com/assets.png/reference", &ExtractExtensions::All,
+      );
+      assert_eq!(ext.map(|ext| ext.without_period().to_string()), None);
+    }
+  }
+
   #[test]
   fn all_extracts_any_extension() {
     let ext = extract_extension_from_url_str("https://example.com/file.png", &ExtractExtensions::All);