diff --git a/src/browser/Factory.zig b/src/browser/Factory.zig
index c5ede22b..582291a3 100644
--- a/src/browser/Factory.zig
+++ b/src/browser/Factory.zig
@@ -247,16 +247,15 @@ fn eventInit(arena: Allocator, typ: String, value: anytype) !Event {
     };
 }
 
-pub fn blob(self: *Factory, child: anytype) !*@TypeOf(child) {
-    const allocator = self._slab.allocator();
-
+pub fn blob(_: *const Factory, arena: Allocator, child: anytype) !*@TypeOf(child) {
     // Special case: Blob has slice and mime fields, so we need manual setup
     const chain = try PrototypeChain(
         &.{ Blob, @TypeOf(child) },
-    ).allocate(allocator);
+    ).allocate(arena);
 
     const blob_ptr = chain.get(0);
     blob_ptr.* = .{
+        ._arena = arena,
         ._type = unionInit(Blob.Type, chain.get(1)),
         ._slice = "",
         ._mime = "",
diff --git a/src/browser/webapi/Blob.zig b/src/browser/webapi/Blob.zig
index aa955ce5..5b8bf81c 100644
--- a/src/browser/webapi/Blob.zig
+++ b/src/browser/webapi/Blob.zig
@@ -21,8 +21,12 @@ const Writer = std.Io.Writer;
 
 const js = @import("../js/js.zig");
 const Page = @import("../Page.zig");
+const Session = @import("../Session.zig");
+
 const Mime = @import("../Mime.zig");
 
+const Allocator = std.mem.Allocator;
+
 /// https://w3c.github.io/FileAPI/#blob-section
 /// https://developer.mozilla.org/en-US/docs/Web/API/Blob
 const Blob = @This();
@@ -31,6 +35,8 @@ pub const _prototype_root = true;
 
 _type: Type,
 
+_arena: Allocator,
+
 /// Immutable slice of blob.
 /// Note that another blob may hold a pointer/slice to this,
 /// so its better to leave the deallocation of it to arena allocator.
@@ -69,6 +75,9 @@ pub fn initWithMimeValidation(
     validate_mime: bool,
     page: *Page,
 ) !*Blob {
+    const arena = try page.getArena(.{ .debug = "Blob" });
+    errdefer page.releaseArena(arena);
+
     const options: InitOptions = maybe_options orelse .{};
 
     const mime: []const u8 = blk: {
@@ -77,7 +86,7 @@ pub fn initWithMimeValidation(
             break :blk "";
         }
 
-        const buf = try page.arena.dupe(u8, t);
+        const buf = try arena.dupe(u8, t);
 
         if (validate_mime) {
             // Full MIME parsing per MIME sniff spec (for Content-Type headers)
@@ -99,7 +108,7 @@ pub fn initWithMimeValidation(
 
     const data = blk: {
         if (maybe_blob_parts) |blob_parts| {
-            var w: Writer.Allocating = .init(page.arena);
+            var w: Writer.Allocating = .init(arena);
             const use_native_endings = std.mem.eql(u8, options.endings, "native");
             try writeBlobParts(&w.writer, blob_parts, use_native_endings);
 
@@ -109,11 +118,19 @@ pub fn initWithMimeValidation(
         break :blk "";
     };
 
-    return page._factory.create(Blob{
+    const self = try arena.create(Blob);
+    self.* = .{
+        ._arena = arena,
         ._type = .generic,
         ._slice = data,
         ._mime = mime,
-    });
+    };
+    return self;
+}
+
+pub fn deinit(self: *Blob, shutdown: bool, session: *Session) void {
+    _ = shutdown;
+    session.releaseArena(self._arena);
 }
 
 const largest_vector = @max(std.simd.suggestVectorLength(u8) orelse 1, 8);
@@ -264,57 +281,31 @@ pub fn bytes(self: *const Blob, page: *Page) !js.Promise {
 /// from a subset of the blob on which it's called.
 pub fn slice(
     self: *const Blob,
-    maybe_start: ?i32,
-    maybe_end: ?i32,
-    maybe_content_type: ?[]const u8,
+    start_: ?i32,
+    end_: ?i32,
+    content_type_: ?[]const u8,
     page: *Page,
 ) !*Blob {
-    const mime: []const u8 = blk: {
-        if (maybe_content_type) |content_type| {
-            if (content_type.len == 0) {
-                break :blk "";
-            }
+    const data = self._slice;
 
-            break :blk try page.dupeString(content_type);
+    const start = blk: {
+        const requested_start = start_ orelse break :blk 0;
+        if (requested_start < 0) {
+            break :blk data.len -| @abs(requested_start);
         }
-
-        break :blk "";
+        break :blk @min(data.len, @as(u31, @intCast(requested_start)));
     };
 
-    const data = self._slice;
-    if (maybe_start) |_start| {
-        const start = blk: {
-            if (_start < 0) {
-                break :blk data.len -| @abs(_start);
-            }
+    const end: usize = blk: {
+        const requested_end = end_ orelse break :blk data.len;
+        if (requested_end < 0) {
+            break :blk @max(start, data.len -| @abs(requested_end));
+        }
 
-            break :blk @min(data.len, @as(u31, @intCast(_start)));
-        };
+        break :blk @min(data.len, @max(start, @as(u31, @intCast(requested_end))));
+    };
 
-        const end: usize = blk: {
-            if (maybe_end) |_end| {
-                if (_end < 0) {
-                    break :blk @max(start, data.len -| @abs(_end));
-                }
-
-                break :blk @min(data.len, @max(start, @as(u31, @intCast(_end))));
-            }
-
-            break :blk data.len;
-        };
-
-        return page._factory.create(Blob{
-            ._type = .generic,
-            ._slice = data[start..end],
-            ._mime = mime,
-        });
-    }
-
-    return page._factory.create(Blob{
-        ._type = .generic,
-        ._slice = data,
-        ._mime = mime,
-    });
+    return Blob.init(&.{data[start..end]}, .{ .type = content_type_ orelse "" }, page);
 }
 
 /// Returns the size of the Blob in bytes.
@@ -334,6 +325,8 @@ pub const JsApi = struct {
         pub const name = "Blob";
         pub const prototype_chain = bridge.prototypeChain();
         pub var class_id: bridge.ClassId = undefined;
+        pub const weak = true;
+        pub const finalizer = bridge.finalizer(Blob.deinit);
     };
 
     pub const constructor = bridge.constructor(Blob.init, .{});
diff --git a/src/browser/webapi/File.zig b/src/browser/webapi/File.zig
index a67a8a6f..f41e44bb 100644
--- a/src/browser/webapi/File.zig
+++ b/src/browser/webapi/File.zig
@@ -18,9 +18,11 @@
 
 const std = @import("std");
 
-const Page = @import("../Page.zig");
-const Blob = @import("Blob.zig");
 const js = @import("../js/js.zig");
+const Page = @import("../Page.zig");
+const Session = @import("../Session.zig");
+
+const Blob = @import("Blob.zig");
 
 const File = @This();
 
@@ -29,7 +31,13 @@ _proto: *Blob,
 
 // TODO: Implement File API.
 pub fn init(page: *Page) !*File {
-    return page._factory.blob(File{ ._proto = undefined });
+    const arena = try page.getArena(.{ .debug = "File" });
+    errdefer page.releaseArena(arena);
+    return page._factory.blob(arena, File{ ._proto = undefined });
+}
+
+pub fn deinit(self: *File, shutdown: bool, session: *Session) void {
+    self._proto.deinit(shutdown, session);
 }
 
 pub const JsApi = struct {
@@ -39,6 +47,8 @@ pub const JsApi = struct {
         pub const name = "File";
         pub const prototype_chain = bridge.prototypeChain();
         pub var class_id: bridge.ClassId = undefined;
+        pub const weak = true;
+        pub const finalizer = bridge.finalizer(File.deinit);
     };
 
     pub const constructor = bridge.constructor(File.init, .{});