diff --git a/core/any_error.rs b/core/any_error.rs
deleted file mode 100644
index 34709e77fc..0000000000
--- a/core/any_error.rs
+++ /dev/null
@@ -1,71 +0,0 @@
-// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-
-use std::any::Any;
-use std::any::TypeId;
-use std::convert::From;
-use std::error::Error;
-use std::fmt;
-use std::ops::Deref;
-
-// The Send and Sync traits are required because deno is multithreaded and we
-// need to be able to handle errors across threads.
-pub trait AnyError: Any + Error + Send + Sync + 'static {}
-impl<T> AnyError for T where T: Any + Error + Send + Sync + Sized + 'static {}
-
-#[derive(Debug)]
-pub struct ErrBox(Box<dyn AnyError>);
-
-impl dyn AnyError {
-  pub fn downcast_ref<T: AnyError>(&self) -> Option<&T> {
-    if Any::type_id(self) == TypeId::of::<T>() {
-      let target = self as *const Self as *const T;
-      let target = unsafe { &*target };
-      Some(target)
-    } else {
-      None
-    }
-  }
-}
-
-impl ErrBox {
-  pub fn downcast<T: AnyError>(self) -> Result<T, Self> {
-    if Any::type_id(&*self.0) == TypeId::of::<T>() {
-      let target = Box::into_raw(self.0) as *mut T;
-      let target = unsafe { Box::from_raw(target) };
-      Ok(*target)
-    } else {
-      Err(self)
-    }
-  }
-}
-
-impl AsRef<dyn AnyError> for ErrBox {
-  fn as_ref(&self) -> &dyn AnyError {
-    self.0.as_ref()
-  }
-}
-
-impl Deref for ErrBox {
-  type Target = Box<dyn AnyError>;
-  fn deref(&self) -> &Self::Target {
-    &self.0
-  }
-}
-
-impl<T: AnyError> From<T> for ErrBox {
-  fn from(error: T) -> Self {
-    Self(Box::new(error))
-  }
-}
-
-impl From<Box<dyn AnyError>> for ErrBox {
-  fn from(boxed: Box<dyn AnyError>) -> Self {
-    Self(boxed)
-  }
-}
-
-impl fmt::Display for ErrBox {
-  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-    self.0.fmt(f)
-  }
-}
diff --git a/core/bindings.rs b/core/bindings.rs
index 16e78e368f..22f6767e85 100644
--- a/core/bindings.rs
+++ b/core/bindings.rs
@@ -1,9 +1,9 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-use crate::es_isolate::EsIsolate;
-use crate::isolate::CoreIsolate;
-use crate::isolate::ZeroCopyBuf;
-use crate::js_errors::JSError;
+use crate::CoreIsolate;
+use crate::EsIsolate;
+use crate::JSError;
+use crate::ZeroCopyBuf;
 
 use rusty_v8 as v8;
 use v8::MapFnTo;
diff --git a/core/isolate.rs b/core/core_isolate.rs
similarity index 93%
rename from core/isolate.rs
rename to core/core_isolate.rs
index 13892c2d9a..12495e2d22 100644
--- a/core/isolate.rs
+++ b/core/core_isolate.rs
@@ -7,13 +7,14 @@
 
 use rusty_v8 as v8;
 
-use crate::any_error::ErrBox;
 use crate::bindings;
-use crate::js_errors::JSError;
 use crate::ops::*;
 use crate::shared_queue::SharedQueue;
 use crate::shared_queue::RECOMMENDED_SIZE;
+use crate::ErrBox;
+use crate::JSError;
 use crate::ResourceTable;
+use crate::ZeroCopyBuf;
 use futures::future::FutureExt;
 use futures::stream::select;
 use futures::stream::FuturesUnordered;
@@ -24,10 +25,7 @@ use libc::c_void;
 use std::cell::RefCell;
 use std::collections::HashMap;
 use std::convert::From;
-use std::error::Error;
-use std::fmt;
 use std::mem::forget;
-use std::ops::{Deref, DerefMut};
 use std::option::Option;
 use std::pin::Pin;
 use std::rc::Rc;
@@ -37,69 +35,6 @@ use std::task::Poll;
 
 type PendingOpFuture = Pin<Box<dyn Future<Output = (OpId, Buf)>>>;
 
-/// A ZeroCopyBuf encapsulates a slice that's been borrowed from a JavaScript
-/// ArrayBuffer object. JavaScript objects can normally be garbage collected,
-/// but the existence of a ZeroCopyBuf inhibits this until it is dropped. It
-/// behaves much like an Arc<[u8]>, although a ZeroCopyBuf currently can't be
-/// cloned.
-pub struct ZeroCopyBuf {
-  backing_store: v8::SharedRef<v8::BackingStore>,
-  byte_offset: usize,
-  byte_length: usize,
-}
-
-unsafe impl Send for ZeroCopyBuf {}
-
-impl ZeroCopyBuf {
-  pub fn new(view: v8::Local<v8::ArrayBufferView>) -> Self {
-    let backing_store = view.buffer().unwrap().get_backing_store();
-    let byte_offset = view.byte_offset();
-    let byte_length = view.byte_length();
-    Self {
-      backing_store,
-      byte_offset,
-      byte_length,
-    }
-  }
-}
-
-impl Deref for ZeroCopyBuf {
-  type Target = [u8];
-  fn deref(&self) -> &[u8] {
-    unsafe {
-      bindings::get_backing_store_slice(
-        &self.backing_store,
-        self.byte_offset,
-        self.byte_length,
-      )
-    }
-  }
-}
-
-impl DerefMut for ZeroCopyBuf {
-  fn deref_mut(&mut self) -> &mut [u8] {
-    unsafe {
-      bindings::get_backing_store_slice_mut(
-        &self.backing_store,
-        self.byte_offset,
-        self.byte_length,
-      )
-    }
-  }
-}
-
-impl AsRef<[u8]> for ZeroCopyBuf {
-  fn as_ref(&self) -> &[u8] {
-    &*self
-  }
-}
-
-impl AsMut<[u8]> for ZeroCopyBuf {
-  fn as_mut(&mut self) -> &mut [u8] {
-    &mut *self
-  }
-}
-
 /// Stores a script used to initialize a Isolate
 pub struct Script<'a> {
   pub source: &'a str,
@@ -627,14 +562,6 @@ fn drain_macrotasks<'s>(
   Ok(())
 }
 
-pub(crate) fn attach_handle_to_error(
-  scope: &mut impl v8::InIsolate,
-  err: ErrBox,
-  handle: v8::Local<v8::Value>,
-) -> ErrBox {
-  ErrWithV8Handle::new(scope, err, handle).into()
-}
-
 pub(crate) fn exception_to_err_result<'s, T>(
   scope: &mut impl v8::ToLocal<'s>,
   exception: v8::Local<v8::Value>,
@@ -1183,42 +1110,3 @@ pub mod tests {
     js_check(isolate2.execute("check.js", "if (a != 3) throw Error('x')"));
   }
 }
-
-// TODO(piscisaureus): rusty_v8 should implement the Error trait on
-// values of type v8::Global<T>.
-pub struct ErrWithV8Handle {
-  err: ErrBox,
-  handle: v8::Global<v8::Value>,
-}
-
-impl ErrWithV8Handle {
-  pub fn new(
-    scope: &mut impl v8::InIsolate,
-    err: ErrBox,
-    handle: v8::Local<v8::Value>,
-  ) -> Self {
-    let handle = v8::Global::new_from(scope, handle);
-    Self { err, handle }
-  }
-
-  pub fn get_handle(&self) -> &v8::Global<v8::Value> {
-    &self.handle
-  }
-}
-
-unsafe impl Send for ErrWithV8Handle {}
-unsafe impl Sync for ErrWithV8Handle {}
-
-impl Error for ErrWithV8Handle {}
-
-impl fmt::Display for ErrWithV8Handle {
-  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-    self.err.fmt(f)
-  }
-}
-
-impl fmt::Debug for ErrWithV8Handle {
-  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-    self.err.fmt(f)
-  }
-}
diff --git a/core/js_errors.rs b/core/errors.rs
similarity index 81%
rename from core/js_errors.rs
rename to core/errors.rs
index e8ea5a342f..bc821b266f 100644
--- a/core/js_errors.rs
+++ b/core/errors.rs
@@ -1,11 +1,76 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-use crate::ErrBox;
 use rusty_v8 as v8;
+use std::any::Any;
+use std::any::TypeId;
 use std::convert::TryFrom;
 use std::convert::TryInto;
 use std::error::Error;
 use std::fmt;
+use std::ops::Deref;
+
+// The Send and Sync traits are required because deno is multithreaded and we
+// need to be able to handle errors across threads.
+pub trait AnyError: Any + Error + Send + Sync + 'static {}
+impl<T> AnyError for T where T: Any + Error + Send + Sync + Sized + 'static {}
+
+#[derive(Debug)]
+pub struct ErrBox(Box<dyn AnyError>);
+
+impl dyn AnyError {
+  pub fn downcast_ref<T: AnyError>(&self) -> Option<&T> {
+    if Any::type_id(self) == TypeId::of::<T>() {
+      let target = self as *const Self as *const T;
+      let target = unsafe { &*target };
+      Some(target)
+    } else {
+      None
+    }
+  }
+}
+
+impl ErrBox {
+  pub fn downcast<T: AnyError>(self) -> Result<T, Self> {
+    if Any::type_id(&*self.0) == TypeId::of::<T>() {
+      let target = Box::into_raw(self.0) as *mut T;
+      let target = unsafe { Box::from_raw(target) };
+      Ok(*target)
+    } else {
+      Err(self)
+    }
+  }
+}
+
+impl AsRef<dyn AnyError> for ErrBox {
+  fn as_ref(&self) -> &dyn AnyError {
+    self.0.as_ref()
+  }
+}
+
+impl Deref for ErrBox {
+  type Target = Box<dyn AnyError>;
+  fn deref(&self) -> &Self::Target {
+    &self.0
+  }
+}
+
+impl<T: AnyError> From<T> for ErrBox {
+  fn from(error: T) -> Self {
+    Self(Box::new(error))
+  }
+}
+
+impl From<Box<dyn AnyError>> for ErrBox {
+  fn from(boxed: Box<dyn AnyError>) -> Self {
+    Self(boxed)
+  }
+}
+
+impl fmt::Display for ErrBox {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    self.0.fmt(f)
+  }
+}
 
 /// A `JSError` represents an exception coming from V8, with stack frames and
 /// line numbers. The deno_cli crate defines another `JSError` type, which wraps
@@ -298,3 +363,50 @@ impl fmt::Display for JSError {
     Ok(())
   }
 }
+
+pub(crate) fn attach_handle_to_error(
+  scope: &mut impl v8::InIsolate,
+  err: ErrBox,
+  handle: v8::Local<v8::Value>,
+) -> ErrBox {
+  ErrWithV8Handle::new(scope, err, handle).into()
+}
+
+// TODO(piscisaureus): rusty_v8 should implement the Error trait on
+// values of type v8::Global<T>.
+pub struct ErrWithV8Handle {
+  err: ErrBox,
+  handle: v8::Global<v8::Value>,
+}
+
+impl ErrWithV8Handle {
+  pub fn new(
+    scope: &mut impl v8::InIsolate,
+    err: ErrBox,
+    handle: v8::Local<v8::Value>,
+  ) -> Self {
+    let handle = v8::Global::new_from(scope, handle);
+    Self { err, handle }
+  }
+
+  pub fn get_handle(&self) -> &v8::Global<v8::Value> {
+    &self.handle
+  }
+}
+
+unsafe impl Send for ErrWithV8Handle {}
+unsafe impl Sync for ErrWithV8Handle {}
+
+impl Error for ErrWithV8Handle {}
+
+impl fmt::Display for ErrWithV8Handle {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    self.err.fmt(f)
+  }
+}
+
+impl fmt::Debug for ErrWithV8Handle {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    self.err.fmt(f)
+  }
+}
diff --git a/core/es_isolate.rs b/core/es_isolate.rs
index 73ff1c388d..a3775c8a43 100644
--- a/core/es_isolate.rs
+++ b/core/es_isolate.rs
@@ -6,10 +6,10 @@
 
 use rusty_v8 as v8;
 
-use crate::any_error::ErrBox;
 use crate::bindings;
+use crate::errors::ErrBox;
+use crate::errors::ErrWithV8Handle;
 use crate::futures::FutureExt;
-use crate::ErrWithV8Handle;
 use futures::ready;
 use futures::stream::FuturesUnordered;
 use futures::stream::StreamExt;
@@ -26,20 +26,19 @@ use std::rc::Rc;
 use std::task::Context;
 use std::task::Poll;
 
-use crate::isolate::attach_handle_to_error;
-use crate::isolate::exception_to_err_result;
-use crate::isolate::CoreIsolate;
-use crate::isolate::StartupData;
+use crate::core_isolate::exception_to_err_result;
+use crate::errors::attach_handle_to_error;
 use crate::module_specifier::ModuleSpecifier;
 use crate::modules::LoadState;
+use crate::modules::ModuleId;
+use crate::modules::ModuleLoadId;
 use crate::modules::ModuleLoader;
 use crate::modules::ModuleSource;
 use crate::modules::Modules;
 use crate::modules::PrepareLoadFuture;
 use crate::modules::RecursiveModuleLoad;
-
-pub type ModuleId = i32;
-pub type ModuleLoadId = i32;
+use crate::CoreIsolate;
+use crate::StartupData;
 
 /// More specialized version of `CoreIsolate` that provides loading
 /// and execution of ES Modules.
@@ -597,11 +596,11 @@ impl Future for EsIsolate {
 #[cfg(test)]
 pub mod tests {
   use super::*;
-  use crate::isolate::js_check;
-  use crate::isolate::tests::run_in_task;
-  use crate::isolate::ZeroCopyBuf;
+  use crate::core_isolate::tests::run_in_task;
+  use crate::js_check;
   use crate::modules::ModuleSourceFuture;
   use crate::ops::*;
+  use crate::ZeroCopyBuf;
   use std::io;
   use std::sync::atomic::{AtomicUsize, Ordering};
   use std::sync::Arc;
diff --git a/core/lib.rs b/core/lib.rs
index ffccc8febb..49d49e19d8 100644
--- a/core/lib.rs
+++ b/core/lib.rs
@@ -8,30 +8,44 @@ extern crate lazy_static;
 #[macro_use]
 extern crate log;
 
-mod any_error;
 mod bindings;
+mod core_isolate;
+mod errors;
 mod es_isolate;
 mod flags;
-mod isolate;
-mod js_errors;
 mod module_specifier;
 mod modules;
 mod ops;
 pub mod plugin_api;
 mod resources;
 mod shared_queue;
+mod zero_copy_buf;
 
 pub use rusty_v8 as v8;
 
-pub use crate::any_error::*;
-pub use crate::es_isolate::*;
+pub use crate::core_isolate::js_check;
+pub use crate::core_isolate::CoreIsolate;
+pub use crate::core_isolate::Script;
+pub use crate::core_isolate::Snapshot;
+pub use crate::core_isolate::StartupData;
+pub use crate::errors::ErrBox;
+pub use crate::errors::JSError;
+pub use crate::es_isolate::EsIsolate;
 pub use crate::flags::v8_set_flags;
-pub use crate::isolate::*;
-pub use crate::js_errors::*;
-pub use crate::module_specifier::*;
-pub use crate::modules::*;
-pub use crate::ops::*;
-pub use crate::resources::*;
+pub use crate::module_specifier::ModuleResolutionError;
+pub use crate::module_specifier::ModuleSpecifier;
+pub use crate::modules::ModuleId;
+pub use crate::modules::ModuleLoadId;
+pub use crate::modules::ModuleLoader;
+pub use crate::modules::ModuleSource;
+pub use crate::modules::ModuleSourceFuture;
+pub use crate::modules::RecursiveModuleLoad;
+pub use crate::ops::Buf;
+pub use crate::ops::Op;
+pub use crate::ops::OpAsyncFuture;
+pub use crate::ops::OpId;
+pub use crate::resources::ResourceTable;
+pub use crate::zero_copy_buf::ZeroCopyBuf;
 
 pub fn v8_version() -> &'static str {
   v8::V8::get_version()
diff --git a/core/modules.rs b/core/modules.rs
index 632df2dd00..5a00d92cc2 100644
--- a/core/modules.rs
+++ b/core/modules.rs
@@ -2,10 +2,8 @@
 
 use rusty_v8 as v8;
 
-use crate::any_error::ErrBox;
-use crate::es_isolate::ModuleId;
-use crate::es_isolate::ModuleLoadId;
 use crate::module_specifier::ModuleSpecifier;
+use crate::ErrBox;
 use futures::future::FutureExt;
 use futures::stream::FuturesUnordered;
 use futures::stream::Stream;
@@ -25,6 +23,9 @@ lazy_static! {
   pub static ref NEXT_LOAD_ID: AtomicI32 = AtomicI32::new(0);
 }
 
+pub type ModuleId = i32;
+pub type ModuleLoadId = i32;
+
 /// EsModule source code that will be loaded into V8.
 ///
 /// Users can implement `Into<ModuleInfo>` for different file types that
@@ -548,7 +549,8 @@ macro_rules! include_crate_modules {
 mod tests {
   use super::*;
   use crate::es_isolate::EsIsolate;
-  use crate::isolate::js_check;
+  use crate::js_check;
+  use crate::StartupData;
   use futures::future::FutureExt;
   use std::error::Error;
   use std::fmt;
@@ -556,6 +558,12 @@ mod tests {
   use std::sync::Arc;
   use std::sync::Mutex;
 
+  // TODO(ry) Sadly FuturesUnordered requires the current task to be set. So
+  // even though we are only using poll() in these tests and not Tokio, we must
+  // nevertheless run it in the tokio executor. Ideally run_in_task can be
+  // removed in the future.
+  use crate::core_isolate::tests::run_in_task;
+
   struct MockLoader {
     pub loads: Arc<Mutex<Vec<String>>>,
   }
@@ -716,13 +724,6 @@ mod tests {
     if (import.meta.url != 'file:///d.js') throw Error();
   "#;
 
-  // TODO(ry) Sadly FuturesUnordered requires the current task to be set. So
-  // even though we are only using poll() in these tests and not Tokio, we must
-  // nevertheless run it in the tokio executor. Ideally run_in_task can be
-  // removed in the future.
-  use crate::isolate::tests::run_in_task;
-  use crate::isolate::StartupData;
-
   #[test]
   fn test_recursive_load() {
     let loader = MockLoader::new();
diff --git a/core/zero_copy_buf.rs b/core/zero_copy_buf.rs
new file mode 100644
index 0000000000..b10c14045b
--- /dev/null
+++ b/core/zero_copy_buf.rs
@@ -0,0 +1,67 @@
+use crate::bindings;
+use rusty_v8 as v8;
+use std::ops::Deref;
+use std::ops::DerefMut;
+
+/// A ZeroCopyBuf encapsulates a slice that's been borrowed from a JavaScript
+/// ArrayBuffer object. JavaScript objects can normally be garbage collected,
+/// but the existence of a ZeroCopyBuf inhibits this until it is dropped. It
+/// behaves much like an Arc<[u8]>, although a ZeroCopyBuf currently can't be
+/// cloned.
+pub struct ZeroCopyBuf {
+  backing_store: v8::SharedRef<v8::BackingStore>,
+  byte_offset: usize,
+  byte_length: usize,
+}
+
+unsafe impl Send for ZeroCopyBuf {}
+
+impl ZeroCopyBuf {
+  pub fn new(view: v8::Local<v8::ArrayBufferView>) -> Self {
+    let backing_store = view.buffer().unwrap().get_backing_store();
+    let byte_offset = view.byte_offset();
+    let byte_length = view.byte_length();
+    Self {
+      backing_store,
+      byte_offset,
+      byte_length,
+    }
+  }
+}
+
+impl Deref for ZeroCopyBuf {
+  type Target = [u8];
+  fn deref(&self) -> &[u8] {
+    unsafe {
+      bindings::get_backing_store_slice(
+        &self.backing_store,
+        self.byte_offset,
+        self.byte_length,
+      )
+    }
+  }
+}
+
+impl DerefMut for ZeroCopyBuf {
+  fn deref_mut(&mut self) -> &mut [u8] {
+    unsafe {
+      bindings::get_backing_store_slice_mut(
+        &self.backing_store,
+        self.byte_offset,
+        self.byte_length,
+      )
+    }
+  }
+}
+
+impl AsRef<[u8]> for ZeroCopyBuf {
+  fn as_ref(&self) -> &[u8] {
+    &*self
+  }
+}
+
+impl AsMut<[u8]> for ZeroCopyBuf {
+  fn as_mut(&mut self) -> &mut [u8] {
+    &mut *self
+  }
+}