diff --git a/Dockerfile b/Dockerfile
index 019ba42971..4801f79c69 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -17,8 +17,8 @@ FROM opendevorg/python-builder as builder
 
 # Optional location of Zuul API endpoint.
 ARG REACT_APP_ZUUL_API
-# Optional flag to disable React Service Worker. (set to true to disable)
-ARG REACT_APP_DISABLE_SERVICE_WORKER
+# Optional flag to enable React Service Worker. (set to true to enable)
+ARG REACT_APP_ENABLE_SERVICE_WORKER
 
 COPY . /tmp/src
 RUN /tmp/src/tools/install-js-tools.sh
diff --git a/doc/source/developer/javascript.rst b/doc/source/developer/javascript.rst
index 72b88657e4..ae39663e8d 100644
--- a/doc/source/developer/javascript.rst
+++ b/doc/source/developer/javascript.rst
@@ -193,6 +193,7 @@ As long as `yarn`_ is installed, the installation of zuul will run
 .. _Patternfly: https://www.patternfly.org/
 .. _create-react-app: https://github.com/facebook/create-react-app/blob/master/packages/react-scripts/template/README.md
 
-In some cases there is the need to disable the service worker which does
-advanced caching. In order to do that set the environment variable
-``REACT_APP_DISABLE_SERVICE_WORKER=true`` during installation.
+By default, zuul-web provides a Progressive Web Application but does
+not run a Service Worker. For deployers who would like to enable one,
+set the environment variable
+``REACT_APP_ENABLE_SERVICE_WORKER=true`` during installation.
diff --git a/releasenotes/notes/service-worker-default-b6f6d5c277657ced.yaml b/releasenotes/notes/service-worker-default-b6f6d5c277657ced.yaml
new file mode 100644
index 0000000000..a98fc2b07c
--- /dev/null
+++ b/releasenotes/notes/service-worker-default-b6f6d5c277657ced.yaml
@@ -0,0 +1,6 @@
+---
+upgrade:
+  - |
+    Service Workers are now disabled by default in the Javascript
+    dashboard. Deployers who wish to enable them need to set
+    ``REACT_APP_ENABLE_SERVICE_WORKER``
diff --git a/web/src/registerServiceWorker.js b/web/src/registerServiceWorker.js
index 3180adeb70..483e5d54df 100644
--- a/web/src/registerServiceWorker.js
+++ b/web/src/registerServiceWorker.js
@@ -21,8 +21,9 @@ const isLocalhost = Boolean(
 )
 
 export default function register () {
-  if (process.env.REACT_APP_DISABLE_SERVICE_WORKER === 'true') {
+  if (process.env.REACT_APP_ENABLE_SERVICE_WORKER !== 'true') {
     console.log('Disabled service worker')
+    unregister()
     return
   }