diff --git a/.pylintrc b/.pylintrc
index fba35186cc..fcf0968f10 100644
--- a/.pylintrc
+++ b/.pylintrc
@@ -57,7 +57,8 @@ confidence=
 disable=fixme,
         missing-docstring,
         invalid-name,
-        too-many-lines
+        too-many-lines,
+        old-style-class
 # Enable the message, report, category or checker with the given id(s). You can
 # either give multiple identifier separated by comma (,) or put this option
 # multiple time (only on the command line, not in the configuration file where
diff --git a/dash/_utils.py b/dash/_utils.py
index 17dc247ebe..d91eab8a86 100644
--- a/dash/_utils.py
+++ b/dash/_utils.py
@@ -1,3 +1,24 @@
+import functools
+import hashlib
+import base64
+import pkgutil
+
+
+def memoize(func):
+    results = {}
+
+    @functools.wraps(func)
+    def wrapper(*args, **kwargs):
+        key = hash((args, frozenset(kwargs.items())))
+        cached = results.get(key)
+        if cached:
+            return cached
+        results[key] = r = func(*args, **kwargs)
+        return r
+
+    return wrapper
+
+
 def interpolate_str(template, **data):
     s = template
     for k, v in data.items():
@@ -37,6 +58,37 @@ def get_asset_path(
     ])
 
 
+def pluck(obj, *props, **additions):
+    return dict({k: v for k, v in obj.items() if k in props}, **additions)
+
+
+def first_key(data, *keys):
+    for key in keys:
+        value = data.get(key)
+        if value:
+            return key, value
+    return None, None
+
+
+def _integrity_hash(b):
+    h = hashlib.sha384(b)
+
+    return 'sha384-{}'.format(
+        base64.b64encode(h.digest()).decode()
+    )
+
+
+@memoize
+def integrity_hash_from_file(filename):
+    with open(filename, 'rb') as f:
+        return _integrity_hash(f.read())
+
+
+@memoize
+def integrity_hash_from_package(namespace, path):
+    return _integrity_hash(pkgutil.get_data(namespace, path))
+
+
 class AttributeDict(dict):
     """
     Dictionary subclass enabling attribute lookup/assignment of keys/values.
diff --git a/dash/dash.py b/dash/dash.py
index 0a68d70bce..41cd7a1c79 100644
--- a/dash/dash.py
+++ b/dash/dash.py
@@ -25,6 +25,7 @@
 from ._utils import interpolate_str as _interpolate
 from ._utils import format_tag as _format_tag
 from ._utils import get_asset_path as _get_asset_path
+from ._utils import pluck as _pluck
 from . import _configs
 
 
@@ -313,6 +314,7 @@ def _collect_and_register_resources(self, resources):
         def _relative_url_path(relative_package_path='', namespace=''):
 
             # track the registered packages
+            # FIXME it append a new path each time the index is served ?
             if namespace in self.registered_paths:
                 self.registered_paths[namespace].append(relative_package_path)
             else:
@@ -332,23 +334,34 @@ def _relative_url_path(relative_package_path='', namespace=''):
                 modified
             )
 
+        def pack(src, **kwargs):
+            return dict(kwargs, src=src)
+
         srcs = []
         for resource in resources:
             if 'relative_package_path' in resource:
                 if isinstance(resource['relative_package_path'], str):
-                    srcs.append(_relative_url_path(**resource))
+                    srcs.append(
+                        pack(
+                            _relative_url_path(
+                                resource['relative_package_path'],
+                                resource['namespace']),
+                            **resource)
+                    )
                 else:
                     for rel_path in resource['relative_package_path']:
-                        srcs.append(_relative_url_path(
+                        srcs.append(pack(_relative_url_path(
                             relative_package_path=rel_path,
-                            namespace=resource['namespace']
-                        ))
+                            namespace=resource['namespace'],
+                        ), **resource))
             elif 'external_url' in resource:
                 if isinstance(resource['external_url'], str):
-                    srcs.append(resource['external_url'])
+                    srcs.append(
+                        pack(resource['external_url'], **resource)
+                    )
                 else:
                     for url in resource['external_url']:
-                        srcs.append(url)
+                        srcs.append(pack(url))
             elif 'absolute_path' in resource:
                 raise Exception(
                     'Serving files from absolute_path isn\'t supported yet'
@@ -357,7 +370,7 @@ def _relative_url_path(relative_package_path='', namespace=''):
                 static_url = self.get_asset_url(resource['asset_path'])
                 # Add a bust query param
                 static_url += '?m={}'.format(resource['ts'])
-                srcs.append(static_url)
+                srcs.append(pack(static_url, **resource))
         return srcs
 
     def _generate_css_dist_html(self):
@@ -365,7 +378,22 @@ def _generate_css_dist_html(self):
                 self._collect_and_register_resources(self.css.get_all_css())
 
         return '\n'.join([
-            _format_tag('link', link, opened=True)
+            _format_tag(
+                'link',
+                _pluck(
+                    link,
+                    'integrity',
+                    'crossorigin',
+                    'media',
+                    'charset',
+                    'rev',
+                    'target',
+                    'type',
+                    href=link.get('src', link.get('href')),
+                    rel='stylesheet'
+                ),
+                opened=True
+            )
             if isinstance(link, dict)
             else '<link rel="stylesheet" href="{}">'.format(link)
             for link in links
@@ -392,7 +420,15 @@ def _generate_scripts_html(self):
                 ))
 
         return '\n'.join([
-            _format_tag('script', src)
+            _format_tag('script', _pluck(
+                src,
+                'src',
+                'integrity',
+                'crossorigin',
+                'charset',
+                'async',
+                'defer',
+                'type'))
             if isinstance(src, dict)
             else '<script src="{}"></script>'.format(src)
             for src in srcs
@@ -492,7 +528,7 @@ def index(self, *args, **kwargs):  # pylint: disable=unused-argument
         checks = (
             (_re_index_entry_id.search(index), '#react-entry-point'),
             (_re_index_config_id.search(index), '#_dash-configs'),
-            (_re_index_scripts_id.search(index), 'dash-renderer'),
+            # (_re_index_scripts_id.search(index), 'dash-renderer'),
         )
         missing = [missing for check, missing in checks if not check]
 
diff --git a/dash/resources.py b/dash/resources.py
index aa1ce871d9..d9a060ec0f 100644
--- a/dash/resources.py
+++ b/dash/resources.py
@@ -4,6 +4,27 @@
 import os
 
 from .development.base_component import Component
+from ._utils import \
+    first_key, integrity_hash_from_file, integrity_hash_from_package
+
+
+# pylint: disable=inconsistent-return-statements
+def find_unpkg(value, relative_package_paths):
+    # find the local file for a unpkg url.
+    # The structure of the _js_dist/_css_dist does not allow
+    # for easy translation between local and external dependencies.
+    v = value.replace('https://unpkg.com/', '')
+    s = v.split('/')
+    lib, version = s[0].split('@')
+    filename = s[-1]
+    ext = filename.split('.')[-1]
+
+    for i in relative_package_paths:
+        if (i == filename and i not in [
+                'index.js', 'index.css', 'style.css', 'style.min.css',
+                'styles.css', 'styles.min.css']) \
+                or (lib in i and version in i and i.endswith(ext)):
+            return i
 
 
 # pylint: disable=old-style-class
@@ -16,14 +37,17 @@ def __init__(self, resource_name, layout):
     def append_resource(self, resource):
         self._resources.append(resource)
 
+    # pylint: disable=too-many-branches
     def _filter_resources(self, all_resources, dev_bundles=False):
         filtered_resources = []
         for s in all_resources:
             filtered_resource = {}
+            added = False
             if 'namespace' in s:
                 filtered_resource['namespace'] = s['namespace']
             if 'external_url' in s and not self.config.serve_locally:
                 filtered_resource['external_url'] = s['external_url']
+                filtered_resource['local_file'] = s['relative_package_path']
             elif 'dev_package_path' in s and dev_bundles:
                 filtered_resource['relative_package_path'] = (
                     s['dev_package_path']
@@ -36,6 +60,9 @@ def _filter_resources(self, all_resources, dev_bundles=False):
                 filtered_resource['absolute_path'] = s['absolute_path']
             elif 'asset_path' in s:
                 info = os.stat(s['filepath'])
+                filtered_resource['integrity'] = integrity_hash_from_file(
+                    s['filepath'])
+                filtered_resource['crossorigin'] = 'anonymous'
                 filtered_resource['asset_path'] = s['asset_path']
                 filtered_resource['ts'] = info.st_mtime
             elif self.config.serve_locally:
@@ -54,7 +81,41 @@ def _filter_resources(self, all_resources, dev_bundles=False):
                     )
                 )
 
-            filtered_resources.append(filtered_resource)
+            if 'integrity' not in filtered_resource \
+                    and 'namespace' in filtered_resource:
+                key, filename = first_key(
+                    filtered_resource,
+                    'external_url',
+                    'dev_package_path',
+                    'relative_package_path'
+                )
+                if isinstance(filename, list):
+                    # flatten these dependencies and add a hash for each.
+                    for f in filename:
+                        local_file = filtered_resource.get('local_file')
+                        filename = find_unpkg(f, local_file) \
+                            if local_file else f.split('/')[-1]
+                        filtered_resources.append({
+                            key: f,
+                            'integrity': integrity_hash_from_package(
+                                filtered_resource['namespace'],
+                                filename),
+                            'crossorigin': 'anonymous',
+                            'namespace': filtered_resource['namespace']
+                        })
+                        added = True
+                else:
+                    filename = filtered_resource.get(
+                        'local_file', filename.split('/')[-1])
+                    filtered_resource['integrity'] = \
+                        integrity_hash_from_package(
+                            filtered_resource['namespace'],
+                            filename
+                        )
+                    filtered_resource['crossorigin'] = 'anonymous'
+
+            if not added:
+                filtered_resources.append(filtered_resource)
 
         return filtered_resources