diff --git a/src/__tests__/LDClient-localstorage-test.js b/src/__tests__/LDClient-localstorage-test.js
index 4b0da64..0df1ca9 100644
--- a/src/__tests__/LDClient-localstorage-test.js
+++ b/src/__tests__/LDClient-localstorage-test.js
@@ -137,4 +137,125 @@ describe('LDClient local storage', () => {
       });
     });
   });
+
+  describe('bootstrapping from session storage', () => {
+    it('does not try to use session storage if the platform says it is unavailable', async () => {
+      const platform = stubPlatform.defaults();
+      platform.localStorage = null;
+
+      const client = platform.testing.makeClient(envName, user, { bootstrap: 'sessionStorage' });
+      await client.waitForInitialization();
+
+      // should see a flag request to the server right away, as if bootstrap was not specified
+      expect(server.requests.length).toEqual(1);
+
+      expect(platform.testing.logger.output.warn).toEqual([messages.localStorageUnavailable()]);
+    });
+
+    it('uses cached flags if available and requests flags from server after ready', async () => {
+      const platform = stubPlatform.defaults();
+      const json = '{"flag-key": 1}';
+      platform.testing.setLocalStorageImmediately(lsKey, json);
+
+      const client = platform.testing.makeClient(envName, user, { bootstrap: 'sessionStorage' });
+      await client.waitForInitialization();
+
+      expect(client.variation('flag-key')).toEqual(1);
+      expect(server.requests.length).toEqual(1);
+    });
+
+    it('starts with empty flags and requests them from server if there are no cached flags', async () => {
+      const platform = stubPlatform.defaults();
+      server.respondWith(jsonResponse({ 'flag-key': { value: 1 } }));
+
+      const client = platform.testing.makeClient(envName, user, { bootstrap: 'sessionStorage' });
+
+      // don't wait for ready event - verifying that variation() doesn't throw an error if called before ready
+      expect(client.variation('flag-key', 0)).toEqual(0);
+
+      // verify that the flags get requested from LD
+      await client.waitForInitialization();
+      expect(client.variation('flag-key')).toEqual(1);
+    });
+
+    it('should handle sessionStorage.get returning an error', async () => {
+      const platform = stubPlatform.defaults();
+      platform.localStorage.get = () => Promise.reject(new Error());
+      server.respondWith(jsonResponse({ 'enable-foo': { value: true } }));
+
+      const client = platform.testing.makeClient(envName, user, { bootstrap: 'sessionStorage' });
+      await client.waitForInitialization();
+
+      expect(platform.testing.logger.output.warn).toEqual([messages.localStorageUnavailable()]);
+    });
+
+    it('should handle sessionStorage.set returning an error', async () => {
+      const platform = stubPlatform.defaults();
+      platform.localStorage.set = () => Promise.reject(new Error());
+      server.respondWith(jsonResponse({ 'enable-foo': { value: true } }));
+
+      const client = platform.testing.makeClient(envName, user, { bootstrap: 'sessionStorage' });
+      await client.waitForInitialization();
+
+      await asyncSleep(0); // allow any pending async tasks to complete
+
+      expect(platform.testing.logger.output.warn).toEqual([messages.localStorageUnavailable()]);
+    });
+
+    it('should not update cached settings if there was an error fetching flags', async () => {
+      const platform = stubPlatform.defaults();
+      const json = '{"enable-foo": true}';
+      server.respondWith(errorResponse(503));
+      platform.testing.setLocalStorageImmediately(lsKey, json);
+
+      const client = platform.testing.makeClient(envName, user, { bootstrap: 'sessionStorage' });
+      await client.waitForInitialization();
+
+      await asyncSleep(0); // allow any pending async tasks to complete
+
+      const value = platform.testing.getLocalStorageImmediately(lsKey);
+      expect(value).toEqual(json);
+    });
+
+    it('should use hash as sessionStorage key when secure mode is enabled', async () => {
+      const platform = stubPlatform.defaults();
+      server.respondWith(jsonResponse({ 'enable-foo': { value: true } }));
+      const lsKeyHash = 'ld:UNKNOWN_ENVIRONMENT_ID:totallyLegitHash';
+      const client = platform.testing.makeClient(envName, user, {
+        bootstrap: 'sessionStorage',
+        hash: 'totallyLegitHash',
+      });
+
+      await client.waitForInitialization();
+      const value = platform.testing.getLocalStorageImmediately(lsKeyHash);
+      expect(JSON.parse(value)).toEqual({
+        $schema: 1,
+        'enable-foo': { value: true },
+      });
+    });
+
+    it('should clear sessionStorage when user context is changed', async () => {
+      const platform = stubPlatform.defaults();
+      const lsKey2 = 'ld:UNKNOWN_ENVIRONMENT_ID:' + utils.btoa('{"key":"user2"}');
+
+      const user2 = { key: 'user2' };
+      const client = platform.testing.makeClient(envName, user, { bootstrap: 'sessionStorage' });
+
+      server.respondWith(jsonResponse({ 'enable-foo': { value: true } }));
+
+      await client.waitForInitialization();
+
+      await asyncSleep(0); // allow any pending async tasks to complete
+
+      await client.identify(user2);
+
+      const value1 = platform.testing.getLocalStorageImmediately(lsKey);
+      expect(value1).not.toEqual(expect.anything());
+      const value2 = platform.testing.getLocalStorageImmediately(lsKey2);
+      expect(JSON.parse(value2)).toEqual({
+        $schema: 1,
+        'enable-foo': { value: true },
+      });
+    });
+  });
 });
diff --git a/src/index.js b/src/index.js
index 9cbbad6..dacff07 100644
--- a/src/index.js
+++ b/src/index.js
@@ -507,7 +507,10 @@ export function initialize(env, user, specifiedOptions, platform, extraDefaults)
     });
   });
 
-  if (typeof options.bootstrap === 'string' && options.bootstrap.toUpperCase() === 'LOCALSTORAGE') {
+  if (typeof options.bootstrap === 'string' &&
+    // Support local or session storage names being passed as a bootstrap option.
+    ['SESSIONSTORAGE', 'LOCALSTORAGE'].includes(options.bootstrap.toUpperCase())
+  ) {
     if (store) {
       useLocalStorage = true;
     } else {