diff --git a/app/javascript/packs/session-expire-session.ts b/app/javascript/packs/session-expire-session.ts
index e92090085cd..fd94090aeb3 100644
--- a/app/javascript/packs/session-expire-session.ts
+++ b/app/javascript/packs/session-expire-session.ts
@@ -1,10 +1,40 @@
-const expireConfig = document.getElementById('js-expire-session');
+import { extendSession } from '@18f/identity-session';
+import type { CountdownElement } from '@18f/identity-countdown/countdown-element';
+import type { ModalElement } from '@18f/identity-modal';
 
-if (expireConfig && expireConfig.dataset.sessionTimeoutIn) {
-  const sessionTimeoutIn = parseInt(expireConfig.dataset.sessionTimeoutIn, 10) * 1000;
-  const timeoutRefreshPath = expireConfig.dataset.timeoutRefreshPath || '';
+const warningEl = document.getElementById('session-timeout-cntnr')!;
 
-  setTimeout(() => {
+const warning = Number(warningEl.dataset.warning!) * 1000;
+const sessionsURL = warningEl.dataset.sessionsUrl!;
+const sessionTimeout = Number(warningEl.dataset.sessionTimeoutIn!) * 1000;
+const modal = document.querySelector<ModalElement>('lg-modal.session-timeout-modal')!;
+const keepaliveEl = document.getElementById('session-keepalive-btn');
+const countdownEls: NodeListOf<CountdownElement> = modal.querySelectorAll('lg-countdown');
+const timeoutRefreshPath = warningEl.dataset.timeoutRefreshPath || '';
+
+let sessionExpiration = new Date(Date.now() + sessionTimeout);
+
+function showModal() {
+  modal.show();
+  countdownEls.forEach((countdownEl) => {
+    countdownEl.expiration = sessionExpiration;
+    countdownEl.start();
+  });
+}
+
+function keepalive() {
+  const isExpired = new Date() > sessionExpiration;
+  if (isExpired) {
     document.location.href = timeoutRefreshPath;
-  }, sessionTimeoutIn);
+  } else {
+    modal.hide();
+    sessionExpiration = new Date(Date.now() + sessionTimeout);
+
+    setTimeout(showModal, sessionTimeout - warning);
+    countdownEls.forEach((countdownEl) => countdownEl.stop());
+    extendSession(sessionsURL);
+  }
 }
+
+keepaliveEl?.addEventListener('click', keepalive, false);
+setTimeout(showModal, sessionTimeout - warning);
diff --git a/app/views/layouts/application.html.erb b/app/views/layouts/application.html.erb
index 9ca2248b6c8..95c76f2f692 100644
--- a/app/views/layouts/application.html.erb
+++ b/app/views/layouts/application.html.erb
@@ -30,6 +30,8 @@
     <%= render partial: 'session_timeout/expire_session',
                locals: {
                  session_timeout_in: Devise.timeout_in,
+                 warning: session_timeout_warning,
+                 modal: session_modal,
                } %>
   <% end %>
 
diff --git a/app/views/session_timeout/_expire_session.html.erb b/app/views/session_timeout/_expire_session.html.erb
index 90dcee3ca62..b68f9ab6972 100644
--- a/app/views/session_timeout/_expire_session.html.erb
+++ b/app/views/session_timeout/_expire_session.html.erb
@@ -1,7 +1,8 @@
-<%= tag.div id: 'js-expire-session',
+<%= tag.div id: 'session-timeout-cntnr',
             data: {
               session_timeout_in: session_timeout_in,
-              timeout_refresh_path: timeout_refresh_path,
+              warning: warning,
+              sessions_url: api_internal_sessions_path,
             } %>
-
+<%= render(partial: 'session_timeout/warning', locals: { modal_presenter: modal }) %>
 <%= javascript_packs_tag_once 'session-expire-session', preload_links_header: false %>
diff --git a/spec/features/users/sign_in_spec.rb b/spec/features/users/sign_in_spec.rb
index 15d4e3abe6d..4228e237c53 100644
--- a/spec/features/users/sign_in_spec.rb
+++ b/spec/features/users/sign_in_spec.rb
@@ -241,6 +241,8 @@
       allow(IdentityConfig.store).to receive(:session_check_delay).and_return(0)
       allow(IdentityConfig.store).to receive(:session_timeout_warning_seconds)
         .and_return(Devise.timeout_in)
+      allow(Devise).to receive(:timeout_in)
+        .and_return(IdentityConfig.store.session_timeout_warning_seconds + 1)
 
       user = create(:user, :fully_registered)
       sign_in_user(user)
@@ -252,22 +254,6 @@
     end
   end
 
-  context 'signed out' do
-    it 'refreshes the current page after session expires', js: true do
-      allow(Devise).to receive(:timeout_in).and_return(1)
-
-      visit sign_up_email_path(request_id: '123abc')
-      fill_in t('forms.registration.labels.email'), with: 'test@example.com'
-
-      expect(page).to have_content(
-        t('notices.session_cleared', minutes: IdentityConfig.store.session_timeout_in_minutes),
-        wait: 5,
-      )
-      expect(page).to have_field(t('forms.registration.labels.email'), with: '')
-      expect(current_url).to match Regexp.escape(sign_up_email_path(request_id: '123abc'))
-    end
-  end
-
   context 'signing back in after session timeout length' do
     around do |example|
       with_forgery_protection { example.run }
@@ -296,19 +282,49 @@
       end
     end
 
-    it 'refreshes the page (which clears the form) and notifies the user', js: true do
-      allow(Devise).to receive(:timeout_in).and_return(1)
-      user = create(:user)
-      visit root_path
-      fill_in t('account.index.email'), with: user.email
-      fill_in 'Password', with: user.password
+    context 'create account' do
+      it 'shows the timeout modal when the session expiration approaches', js: true do
+        allow(Devise).to receive(:timeout_in)
+          .and_return(IdentityConfig.store.session_timeout_warning_seconds + 1)
 
-      expect(page).to have_content(
-        t('notices.session_cleared', minutes: IdentityConfig.store.session_timeout_in_minutes),
-        wait: 5,
-      )
-      expect(find_field('Email').value).to be_blank
-      expect(find_field('Password').value).to be_blank
+        visit sign_up_email_path
+        fill_in t('forms.registration.labels.email'), with: 'test@example.com'
+
+        expect(page).to have_css('.usa-js-modal--active', wait: 10)
+
+        click_button t('notices.timeout_warning.partially_signed_in.continue')
+
+        expect(page).not_to have_css('.usa-js-modal--active')
+        expect(find_field(t('forms.registration.labels.email')).value).not_to be_blank
+      end
+    end
+
+    context 'sign in' do
+      it 'shows the timeout modal when the session expiration approaches', js: true do
+        allow(Devise).to receive(:timeout_in)
+          .and_return(IdentityConfig.store.session_timeout_warning_seconds + 1)
+
+        visit root_path
+        fill_in t('account.index.email'), with: 'test@example.com'
+
+        expect(page).to have_css('.usa-js-modal--active', wait: 10)
+
+        click_button t('notices.timeout_warning.partially_signed_in.continue')
+        expect(find_field(t('account.index.email')).value).not_to be_blank
+      end
+
+      it 'reloads the sign in page when cancel is clicked', js: true do
+        allow(Devise).to receive(:timeout_in)
+          .and_return(IdentityConfig.store.session_timeout_warning_seconds + 1)
+
+        visit root_path
+        fill_in t('account.index.email'), with: 'test@example.com'
+
+        expect(page).to have_css('.usa-js-modal--active', wait: 10)
+
+        click_button t('notices.timeout_warning.partially_signed_in.sign_out')
+        expect(find_field(t('account.index.email')).value).to be_blank
+      end
     end
   end
 
diff --git a/spec/views/layouts/application.html.erb_spec.rb b/spec/views/layouts/application.html.erb_spec.rb
index 0fcedb4c83e..c7565dccf21 100644
--- a/spec/views/layouts/application.html.erb_spec.rb
+++ b/spec/views/layouts/application.html.erb_spec.rb
@@ -15,6 +15,7 @@
       ).create_session,
     )
     allow(view.request).to receive(:original_fullpath).and_return('/foobar')
+    allow(view).to receive(:user_fully_authenticated?).and_return(false)
     view.title = title_content if title_content
   end
 
@@ -123,7 +124,6 @@
 
   context 'session expiration' do
     it 'renders a javascript page refresh' do
-      allow(view).to receive(:user_fully_authenticated?).and_return(false)
       allow(view).to receive(:current_user).and_return(false)
       allow(view).to receive(:decorated_sp_session).and_return(NullServiceProviderSession.new)
       render