diff --git a/services/tunnelbroker/src/Constants.h b/services/tunnelbroker/src/Constants.h
--- a/services/tunnelbroker/src/Constants.h
+++ b/services/tunnelbroker/src/Constants.h
@@ -43,6 +43,8 @@
 // DEVICEID_CHAR_LENGTH has to be kept in sync with deviceIDCharLength
 // which is defined in web/utils/device-id.js
 const size_t DEVICEID_CHAR_LENGTH = 64;
+// DEVICEID_FORMAT_REGEX has to be kept in sync with deviceIDFormatRegex
+// which is defined in web/utils/device-id.js
 const std::regex DEVICEID_FORMAT_REGEX(
     "^(ks|mobile|web):[a-zA-Z0-9]{" + std::to_string(DEVICEID_CHAR_LENGTH) +
     "}$");
diff --git a/web/redux/device-id-reducer.js b/web/redux/device-id-reducer.js
--- a/web/redux/device-id-reducer.js
+++ b/web/redux/device-id-reducer.js
@@ -1,16 +1,12 @@
 // @flow
 
 import type { Action } from '../redux/redux-setup';
-import { deviceIDCharLength } from '../utils//device-id';
+import { deviceIDFormatRegex } from '../utils/device-id';
 import { setDeviceIDActionType } from './action-types';
 
-const deviceIDRegex = new RegExp(
-  `^(ks|mobile|web):[a-zA-Z0-9]{${deviceIDCharLength.toString()}}$`,
-);
-
 export function reduceDeviceID(state: ?string, action: Action): ?string {
   if (action.type === setDeviceIDActionType) {
-    if (action.payload?.match(deviceIDRegex)) {
+    if (action.payload?.match(deviceIDFormatRegex)) {
       return action.payload;
     }
     return null;
diff --git a/web/utils/device-id.js b/web/utils/device-id.js
--- a/web/utils/device-id.js
+++ b/web/utils/device-id.js
@@ -16,6 +16,11 @@
 // deviceIDCharLength has to be kept in sync with DEVICEID_CHAR_LENGTH
 // which is defined in services/tunnelbroker/src/Constants.h
 const deviceIDCharLength = 64;
+// deviceIDFormatRegex has to be kept in sync with DEVICEID_FORMAT_REGEX
+// which is defined in services/tunnelbroker/src/Constants.h
+const deviceIDFormatRegex: RegExp = new RegExp(
+  `^(ks|mobile|web):[a-zA-Z0-9]{${deviceIDCharLength.toString()}}$`,
+);
 
 function generateDeviceID(type: DeviceIDType): string {
   const suffix = generateRandomString(deviceIDCharLength, alphanumeric);
@@ -30,4 +35,9 @@
   invariant(false, `Unhandled device type ${type}`);
 }
 
-export { generateDeviceID, deviceIDCharLength, deviceIDTypes };
+export {
+  generateDeviceID,
+  deviceIDCharLength,
+  deviceIDTypes,
+  deviceIDFormatRegex,
+};
diff --git a/web/utils/device-id.test.js b/web/utils/device-id.test.js
--- a/web/utils/device-id.test.js
+++ b/web/utils/device-id.test.js
@@ -4,17 +4,17 @@
   generateDeviceID,
   deviceIDCharLength,
   deviceIDTypes,
+  deviceIDFormatRegex,
 } from './device-id';
 
 describe('generateDeviceID', () => {
-  const baseRegExp = new RegExp(
-    `^(ks|mobile|web):[a-zA-Z0-9]{${deviceIDCharLength.toString()}}$`,
-  );
   it(
     'passed deviceIDTypes.KEYSERVER retruns a randomly generated string, ' +
       'subject to ^(ks|mobile|web):[a-zA-Z0-9]{DEVICEID_CHAR_LENGTH}$',
     () => {
-      expect(generateDeviceID(deviceIDTypes.KEYSERVER)).toMatch(baseRegExp);
+      expect(generateDeviceID(deviceIDTypes.KEYSERVER)).toMatch(
+        deviceIDFormatRegex,
+      );
     },
   );
 
@@ -22,7 +22,7 @@
     'passed deviceIDTypes.WEB retruns a randomly generated string, ' +
       'subject to ^(ks|mobile|web):[a-zA-Z0-9]{DEVICEID_CHAR_LENGTH}$',
     () => {
-      expect(generateDeviceID(deviceIDTypes.WEB)).toMatch(baseRegExp);
+      expect(generateDeviceID(deviceIDTypes.WEB)).toMatch(deviceIDFormatRegex);
     },
   );
 
@@ -30,7 +30,9 @@
     'passed deviceIDTypes.MOBILE retruns a randomly generated string, ' +
       'subject to ^(ks|mobile|web):[a-zA-Z0-9]{DEVICEID_CHAR_LENGTH}$',
     () => {
-      expect(generateDeviceID(deviceIDTypes.MOBILE)).toMatch(baseRegExp);
+      expect(generateDeviceID(deviceIDTypes.MOBILE)).toMatch(
+        deviceIDFormatRegex,
+      );
     },
   );