1 files changed, 18 insertions, 1 deletions
diff --git a/src/renderer.rs b/src/renderer.rs
index eb39c76..14d30d6 100644
--- a/src/renderer.rs
+++ b/src/renderer.rs
@@ -143,7 +143,12 @@ fn human_readable_size(bytes: u64) -> String {
 }
 
 fn detect_language(filename: &Path) -> &'static str {
-    match filename.extension().and_then(|e| e.to_str()) {
+    let ext = filename
+        .extension()
+        .and_then(|e| e.to_str())
+        .map(|e| e.to_ascii_lowercase());
+    let ext_str = ext.as_deref();
+    match ext_str {
         Some("rs") => "rust",
         Some("py") => "python",
         Some("json") => "json",
@@ -265,6 +270,18 @@ mod tests {
     }
 
     #[test]
+    fn uppercase_extension_is_still_detected() {
+        let mut output = Vec::new();
+        let mut renderer = Renderer::new(&mut output);
+
+        let input = Cursor::new("fn main() {}");
+        renderer.render_file(Path::new("MAIN.RS"), input).unwrap();
+        let expected = "\n## File: MAIN.RS\n```rust\nfn main() {}\n```\n";
+
+        assert_eq!(String::from_utf8(output).unwrap(), expected);
+    }
+
+    #[test]
     fn renderer_places_placeholder_for_large_files_by_default() {
         let mut output = Vec::new();
         let mut renderer = Renderer::new(&mut output).with_max_file_size(5); // smaller than file