diff --git a/Cargo.lock b/Cargo.lock
index 87f90e9..374a9c0 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -641,7 +641,7 @@ dependencies = [
  "serde",
  "serde_spanned",
  "toml_datetime",
- "toml_edit",
+ "toml_edit 0.22.16",
 ]
 
 [[package]]
@@ -663,7 +663,20 @@ dependencies = [
  "serde",
  "serde_spanned",
  "toml_datetime",
- "winnow",
+ "winnow 0.5.40",
+]
+
+[[package]]
+name = "toml_edit"
+version = "0.22.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "278f3d518e152219c994ce877758516bca5e118eaed6996192a774fb9fbf0788"
+dependencies = [
+ "indexmap",
+ "serde",
+ "serde_spanned",
+ "toml_datetime",
+ "winnow 0.6.13",
 ]
 
 [[package]]
@@ -710,7 +723,7 @@ dependencies = [
  "serde",
  "shlex",
  "snapbox",
- "toml_edit",
+ "toml_edit 0.19.15",
 ]
 
 [[package]]
@@ -806,6 +819,7 @@ dependencies = [
  "unic-char-range",
  "unic-ucd-block",
  "unic-ucd-name",
+ "walkdir",
 ]
 
 [[package]]
@@ -989,3 +1003,12 @@ checksum = "557404e450152cd6795bb558bca69e43c585055f4606e3bcae5894fc6dac9ba0"
 dependencies = [
  "memchr",
 ]
+
+[[package]]
+name = "winnow"
+version = "0.6.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "59b5e5f6c299a3c7890b876a2a587f3115162487e704907d9b6cd29473052ba1"
+dependencies = [
+ "memchr",
+]
diff --git a/Cargo.toml b/Cargo.toml
index fb43529..58ac136 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -26,6 +26,7 @@ unic-ucd-block = "0.9.0"
 unic-char-range = "0.9.0"
 toml = "0.8.14"
 serde = { version = "1.0.203", features = ["derive"] }
+walkdir = "2.5.0"
 
 [dev-dependencies]
 trycmd = "0.15.5"
diff --git a/README.md b/README.md
index 04c9512..d6b1bde 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,13 @@
 # Unicop
 
+## Usage
+
+```
+unicop [FILES]...
+```
+
+Where `[FILES]...` is a list of files or directory to check, default: `.`.
+
 ## Example
 
 ```console
diff --git a/src/main.rs b/src/main.rs
index 73fde85..69e8e59 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,33 +1,41 @@
 use std::env;
 use std::fs;
+use std::path::Path;
 
 use miette::{miette, LabeledSpan, NamedSource, Severity};
 use unic_ucd_name::Name;
 
-mod config;
-mod rules;
-
 fn main() {
-    for arg in env::args().skip(1) {
-        check_file(&arg);
+    let mut args: Vec<String> = env::args().skip(1).collect();
+    if args.is_empty() {
+        args = vec![String::from(".")]
+    }
+    for arg in args.iter() {
+        for entry in walkdir::WalkDir::new(arg) {
+            match entry {
+                Err(err) => eprintln!("{:}", err),
+                Ok(entry) if entry.file_type().is_file() => check_file(entry.path()),
+                Ok(_) => {}
+            }
+        }
     }
 }
 
-fn check_file(arg: &str) {
-    let src = fs::read_to_string(arg).unwrap();
-    let nsrc = NamedSource::new(arg, src.clone());
+fn check_file(path: &Path) {
+    let Some(lang) = detect_language(path) else {
+        return;
+    };
+    let filename = path.display().to_string();
+    let src = fs::read_to_string(path).unwrap();
+    let nsrc = NamedSource::new(&filename, src.clone());
     let mut parser = tree_sitter::Parser::new();
-    parser
-        .set_language(&tree_sitter_javascript::language())
-        .expect("Error loading JavaScript grammar");
-    // parser
-    //     .set_language(&tree_sitter_python::language())
-    //     .expect("Error loading Python grammar");
+    parser.set_language(&lang).expect("Error loading grammar");
     let tree = parser.parse(&src, None).unwrap();
     if tree.root_node().has_error() {
         println!(
             "{:?}",
-            miette!(severity = Severity::Warning, "{}: parse error", arg).with_source_code(nsrc)
+            miette!(severity = Severity::Warning, "{}: parse error", filename)
+                .with_source_code(nsrc)
         );
     }
     for (off, ch) in src.char_indices() {
@@ -52,7 +60,23 @@ fn check_file(arg: &str) {
             chname,
             node.kind()
         )
-        .with_source_code(NamedSource::new(arg, src.clone()));
+        .with_source_code(NamedSource::new(&filename, src.clone()));
         println!("{:?}", report);
     }
 }
+
+// Tree-sitter grammars include some configurations to help decide whether the language applies to
+// a given file.
+// Unfortunately, neither the language-detection algorithm nor the configurations are included in
+// the Rust crates. So for now we have a simplified language-detection with hard-coded
+// configurations.
+// See https://tree-sitter.github.io/tree-sitter/syntax-highlighting#language-detection
+fn detect_language(path: &Path) -> Option<tree_sitter::Language> {
+    match path.extension()?.to_str()? {
+        // https://github.com/tree-sitter/tree-sitter-javascript/blob/master/package.json
+        "js" | "mjs" | "cjs" | "jsx" => Some(tree_sitter_javascript::language()),
+        // https://github.com/tree-sitter/tree-sitter-python/blob/master/package.json
+        "py" => Some(tree_sitter_python::language()),
+        _ => None,
+    }
+}