diff --git a/src/assets/js/lib.d.ts b/src/assets/js/lib.d.ts
index 72b9d1f..1cc226b 100644
--- a/src/assets/js/lib.d.ts
+++ b/src/assets/js/lib.d.ts
@@ -488,14 +488,17 @@ interface FileStat {
 interface File {
     readonly pointer: Promise<number>;
     readonly length: Promise<number>;
-    readonly mode: Promise<'' | 'r' | 'rw'>;
 
     read(n: number): Promise<number[]>;
     write(buff: number[]): Promise<void>;
     close(): Promise<void>;
-    setPointer(val: number): Promise<void>;
+    seek(offset: number, whence: number): Promise<void>;
 }
 interface Filesystem {
+    readonly SEEK_SET: 0;
+    readonly SEEK_CUR: 1;
+    readonly SEEK_END: 2;
+
     open(path: string, mode: 'r' | 'rw'): Promise<File>;
     ls(path: string): AsyncIterableIterator<string>;
     mkdir(path: string): Promise<void>;
@@ -503,6 +506,7 @@ interface Filesystem {
     rm(path: string, recursive?: boolean): Promise<void>;
     stat(path: string): Promise<FileStat>;
     exists(path: string): Promise<boolean>;
+    normalize(...paths: string[]): string;
 }
 
 interface Encoding {
@@ -526,6 +530,7 @@ declare var parseInt: typeof Number.parseInt;
 declare var parseFloat: typeof Number.parseFloat;
 
 declare function log(...vals: any[]): void;
+declare function require(name: string): any;
 
 declare var Array: ArrayConstructor;
 declare var Boolean: BooleanConstructor;
diff --git a/src/me/topchetoeu/jscript/Main.java b/src/me/topchetoeu/jscript/Main.java
index db9211c..ca32edd 100644
--- a/src/me/topchetoeu/jscript/Main.java
+++ b/src/me/topchetoeu/jscript/Main.java
@@ -22,6 +22,7 @@ import me.topchetoeu.jscript.filesystem.MemoryFilesystem;
 import me.topchetoeu.jscript.filesystem.Mode;
 import me.topchetoeu.jscript.filesystem.PhysicalFilesystem;
 import me.topchetoeu.jscript.lib.Internals;
+import me.topchetoeu.jscript.modules.ModuleRepo;
 
 public class Main {   
     public static class Printer implements Observer<Object> {
@@ -119,7 +120,8 @@ public class Main {
         }));
 
         environment.filesystem.protocols.put("temp", new MemoryFilesystem(Mode.READ_WRITE));
-        environment.filesystem.protocols.put("file", new PhysicalFilesystem(Path.of(".").toAbsolutePath()));
+        environment.filesystem.protocols.put("file", new PhysicalFilesystem("."));
+        environment.modules.repos.put("file", ModuleRepo.ofFilesystem(environment.filesystem));
     }
     private static void initEngine() {
         debugServer.targets.put("target", (ws, req) -> new SimpleDebugger(ws, engine));
diff --git a/src/me/topchetoeu/jscript/engine/Environment.java b/src/me/topchetoeu/jscript/engine/Environment.java
index 0eb322e..8f6e1bc 100644
--- a/src/me/topchetoeu/jscript/engine/Environment.java
+++ b/src/me/topchetoeu/jscript/engine/Environment.java
@@ -18,10 +18,12 @@ import me.topchetoeu.jscript.interop.Native;
 import me.topchetoeu.jscript.interop.NativeGetter;
 import me.topchetoeu.jscript.interop.NativeSetter;
 import me.topchetoeu.jscript.interop.NativeWrapperProvider;
+import me.topchetoeu.jscript.modules.RootModuleRepo;
 import me.topchetoeu.jscript.parsing.Parsing;
 import me.topchetoeu.jscript.permissions.Permission;
 import me.topchetoeu.jscript.permissions.PermissionsProvider;
 
+// TODO: Remove hardcoded extensions form environment
 public class Environment implements PermissionsProvider {
     private HashMap<String, ObjectValue> prototypes = new HashMap<>();
 
@@ -30,8 +32,11 @@ public class Environment implements PermissionsProvider {
 
     public GlobalScope global;
     public WrappersProvider wrappers;
+
     public PermissionsProvider permissions = null;
     public final RootFilesystem filesystem = new RootFilesystem(this);
+    public final RootModuleRepo modules = new RootModuleRepo();
+    public String moduleCwd = "/";
 
     private static int nextId = 0;
 
@@ -63,11 +68,6 @@ public class Environment implements PermissionsProvider {
         throw EngineException.ofError("Regular expressions not supported.").setCtx(ctx.environment(), ctx.engine);
     });
 
-    public Environment addData(Data data) {
-        this.data.addAll(data);
-        return this;
-    }
-
     @Native public ObjectValue proto(String name) {
         return prototypes.get(name);
     }
@@ -96,6 +96,9 @@ public class Environment implements PermissionsProvider {
     @Native public Environment child() {
         var res = fork();
         res.global = res.global.globalChild();
+        res.permissions = this.permissions;
+        res.filesystem.protocols.putAll(this.filesystem.protocols);
+        res.modules.repos.putAll(this.modules.repos);
         return res;
     }
 
@@ -106,6 +109,10 @@ public class Environment implements PermissionsProvider {
         return permissions == null || permissions.hasPermission(perm);
     }
 
+    public Context context(Engine engine) {
+        return new Context(engine, this);
+    }
+
     public static Symbol getSymbol(String name) {
         if (symbols.containsKey(name)) return symbols.get(name);
         else {
diff --git a/src/me/topchetoeu/jscript/lib/Internals.java b/src/me/topchetoeu/jscript/lib/Internals.java
index 2bc6a26..2059e62 100644
--- a/src/me/topchetoeu/jscript/lib/Internals.java
+++ b/src/me/topchetoeu/jscript/lib/Internals.java
@@ -20,6 +20,12 @@ public class Internals {
     private static final DataKey<HashMap<Integer, Thread>> THREADS = new DataKey<>();
     private static final DataKey<Integer> I = new DataKey<>();
 
+    @Native public static Object require(Context ctx, String name) {
+        var env = ctx.environment();
+        var res = env.modules.getModule(ctx, env.moduleCwd, name);
+        res.load(ctx);
+        return res.value();
+    }
 
     @Native public static Object log(Context ctx, Object ...args) {
         for (var arg : args) {
diff --git a/src/me/topchetoeu/jscript/modules/Module.java b/src/me/topchetoeu/jscript/modules/Module.java
new file mode 100644
index 0000000..938c721
--- /dev/null
+++ b/src/me/topchetoeu/jscript/modules/Module.java
@@ -0,0 +1,20 @@
+package me.topchetoeu.jscript.modules;
+
+import me.topchetoeu.jscript.engine.Context;
+
+public abstract class Module {
+    private Object value;
+    private boolean loaded;
+
+    public Object value() { return value; }
+    public boolean loaded() { return loaded; }
+
+    protected abstract Object onLoad(Context ctx);
+
+    public void load(Context ctx) {
+        if (loaded) return;
+        this.value = onLoad(ctx);
+        this.loaded = true;
+    }
+}
+
diff --git a/src/me/topchetoeu/jscript/modules/ModuleRepo.java b/src/me/topchetoeu/jscript/modules/ModuleRepo.java
new file mode 100644
index 0000000..54a98e1
--- /dev/null
+++ b/src/me/topchetoeu/jscript/modules/ModuleRepo.java
@@ -0,0 +1,32 @@
+package me.topchetoeu.jscript.modules;
+
+import java.util.HashMap;
+
+import me.topchetoeu.jscript.Filename;
+import me.topchetoeu.jscript.engine.Context;
+import me.topchetoeu.jscript.filesystem.Filesystem;
+import me.topchetoeu.jscript.filesystem.Mode;
+
+public interface ModuleRepo {
+    public Module getModule(Context ctx, String cwd, String name);
+
+    public static ModuleRepo ofFilesystem(Filesystem fs) {
+        var modules = new HashMap<String, Module>();
+
+        return (ctx, cwd, name) -> {
+            name = fs.normalize(cwd, name);
+            var filename = Filename.parse(name);
+            var src = fs.open(name, Mode.READ).readToString();
+
+            if (modules.containsKey(name)) return modules.get(name);
+
+            var env = ctx.environment().child();
+            env.moduleCwd = fs.normalize(name, "..");
+
+            var mod = new SourceModule(filename, src, env);
+            modules.put(name, mod);
+
+            return mod;
+        };
+    }
+}
diff --git a/src/me/topchetoeu/jscript/modules/RootModuleRepo.java b/src/me/topchetoeu/jscript/modules/RootModuleRepo.java
new file mode 100644
index 0000000..3b57a63
--- /dev/null
+++ b/src/me/topchetoeu/jscript/modules/RootModuleRepo.java
@@ -0,0 +1,30 @@
+package me.topchetoeu.jscript.modules;
+
+import java.util.HashMap;
+
+import me.topchetoeu.jscript.engine.Context;
+import me.topchetoeu.jscript.exceptions.EngineException;
+
+public class RootModuleRepo implements ModuleRepo {
+    public final HashMap<String, ModuleRepo> repos = new HashMap<>();
+
+    @Override
+    public Module getModule(Context ctx, String cwd, String name) {
+        var i = name.indexOf(":");
+        String repoName, modName;
+
+        if (i < 0) {
+            repoName = "file";
+            modName = name;
+        }
+        else {
+            repoName = name.substring(0, i);
+            modName = name.substring(i + 1);
+        }
+
+        var repo = repos.get(repoName);
+        if (repo == null) throw EngineException.ofError("ModuleError", "Couldn't find module repo '" + repoName + "'.");
+
+        return repo.getModule(ctx, cwd, modName);
+    }
+}
diff --git a/src/me/topchetoeu/jscript/modules/SourceModule.java b/src/me/topchetoeu/jscript/modules/SourceModule.java
new file mode 100644
index 0000000..5971ce1
--- /dev/null
+++ b/src/me/topchetoeu/jscript/modules/SourceModule.java
@@ -0,0 +1,23 @@
+package me.topchetoeu.jscript.modules;
+
+import me.topchetoeu.jscript.Filename;
+import me.topchetoeu.jscript.engine.Context;
+import me.topchetoeu.jscript.engine.Environment;
+
+public class SourceModule extends Module {
+    public final Filename filename;
+    public final String source;
+    public final Environment env;
+
+    @Override
+    protected Object onLoad(Context ctx) {
+        var res = new Context(ctx.engine, env).compile(filename, source);
+        return res.call(ctx);
+    }
+
+    public SourceModule(Filename filename, String source, Environment env) {
+        this.filename = filename;
+        this.source = source;
+        this.env = env;
+    }
+}