diff --git a/native/qr-code/qr-code-screen.react.js b/native/qr-code/qr-code-screen.react.js
--- a/native/qr-code/qr-code-screen.react.js
+++ b/native/qr-code/qr-code-screen.react.js
@@ -9,41 +9,24 @@
 import { useQRAuth } from 'lib/hooks/qr-auth.js';
 import { uintArrayToHexString } from 'lib/media/data-utils.js';
 import { useTunnelbroker } from 'lib/tunnelbroker/tunnelbroker-context.js';
-import type { BackupKeys } from 'lib/types/backup-types.js';
 import { getContentSigningKey } from 'lib/utils/crypto-utils.js';
-import { getMessageForException } from 'lib/utils/errors.js';
 
 import type { QRCodeSignInNavigationProp } from './qr-code-sign-in-navigator.react.js';
 import {
   composeTunnelbrokerQRAuthMessage,
+  handleSecondaryDeviceRegistrationError,
   parseTunnelbrokerQRAuthMessage,
+  performBackupRestore,
 } from './qr-code-utils.js';
-import { commCoreModule } from '../native-modules.js';
 import type { NavigationRoute } from '../navigation/route-names.js';
-import { persistConfig } from '../redux/persist.js';
 import { useStyles } from '../themes/colors.js';
 import * as AES from '../utils/aes-crypto-module.js';
-import {
-  appOutOfDateAlertDetails,
-  unknownErrorAlertDetails,
-} from '../utils/alert-messages.js';
-import Alert from '../utils/alert.js';
 
 type QRCodeScreenProps = {
   +navigation: QRCodeSignInNavigationProp<'QRCodeScreen'>,
   +route: NavigationRoute<'QRCodeScreen'>,
 };
 
-function performBackupRestore(backupKeys: BackupKeys): Promise<void> {
-  const { backupID, backupDataKey, backupLogDataKey } = backupKeys;
-  return commCoreModule.restoreBackupData(
-    backupID,
-    backupDataKey,
-    backupLogDataKey,
-    persistConfig.version.toString(),
-  );
-}
-
 // eslint-disable-next-line no-unused-vars
 function QRCodeScreen(props: QRCodeScreenProps): React.Node {
   const [qrData, setQRData] =
@@ -71,22 +54,7 @@
       try {
         await logInSecondaryDevice(userID);
       } catch (err) {
-        console.error('Secondary device registration error:', err);
-        const messageForException = getMessageForException(err);
-        if (
-          messageForException === 'client_version_unsupported' ||
-          messageForException === 'unsupported_version'
-        ) {
-          Alert.alert(
-            appOutOfDateAlertDetails.title,
-            appOutOfDateAlertDetails.message,
-          );
-        } else {
-          Alert.alert(
-            unknownErrorAlertDetails.title,
-            unknownErrorAlertDetails.message,
-          );
-        }
+        handleSecondaryDeviceRegistrationError(err);
         void generateQRCode();
       }
     },
diff --git a/native/qr-code/qr-code-utils.js b/native/qr-code/qr-code-utils.js
--- a/native/qr-code/qr-code-utils.js
+++ b/native/qr-code/qr-code-utils.js
@@ -1,6 +1,7 @@
 // @flow
 
 import { hexToUintArray } from 'lib/media/data-utils.js';
+import type { BackupKeys } from 'lib/types/backup-types.js';
 import {
   peerToPeerMessageTypes,
   type QRCodeAuthMessage,
@@ -9,13 +10,20 @@
   qrCodeAuthMessagePayloadValidator,
   type QRCodeAuthMessagePayload,
 } from 'lib/types/tunnelbroker/qr-code-auth-message-types.js';
+import { getMessageForException } from 'lib/utils/errors.js';
 
 import {
   convertBytesToObj,
   convertObjToBytes,
 } from '../backup/conversion-utils.js';
-import { commUtilsModule } from '../native-modules.js';
+import { commCoreModule, commUtilsModule } from '../native-modules.js';
+import { persistConfig } from '../redux/persist.js';
 import * as AES from '../utils/aes-crypto-module.js';
+import {
+  appOutOfDateAlertDetails,
+  unknownErrorAlertDetails,
+} from '../utils/alert-messages.js';
+import Alert from '../utils/alert.js';
 
 function composeTunnelbrokerQRAuthMessage(
   encryptionKey: string,
@@ -52,4 +60,38 @@
   return Promise.resolve(payload);
 }
 
-export { composeTunnelbrokerQRAuthMessage, parseTunnelbrokerQRAuthMessage };
+function handleSecondaryDeviceRegistrationError(error: mixed): void {
+  console.error('Secondary device registration error:', error);
+  const messageForException = getMessageForException(error);
+  if (
+    messageForException === 'client_version_unsupported' ||
+    messageForException === 'unsupported_version'
+  ) {
+    Alert.alert(
+      appOutOfDateAlertDetails.title,
+      appOutOfDateAlertDetails.message,
+    );
+  } else {
+    Alert.alert(
+      unknownErrorAlertDetails.title,
+      unknownErrorAlertDetails.message,
+    );
+  }
+}
+
+function performBackupRestore(backupKeys: BackupKeys): Promise<void> {
+  const { backupID, backupDataKey, backupLogDataKey } = backupKeys;
+  return commCoreModule.restoreBackupData(
+    backupID,
+    backupDataKey,
+    backupLogDataKey,
+    persistConfig.version.toString(),
+  );
+}
+
+export {
+  composeTunnelbrokerQRAuthMessage,
+  parseTunnelbrokerQRAuthMessage,
+  handleSecondaryDeviceRegistrationError,
+  performBackupRestore,
+};
diff --git a/web/account/qr-code-login.react.js b/web/account/qr-code-login.react.js
--- a/web/account/qr-code-login.react.js
+++ b/web/account/qr-code-login.react.js
@@ -3,68 +3,20 @@
 import { QRCodeSVG } from 'qrcode.react';
 import * as React from 'react';
 
-import { useModalContext } from 'lib/components/modal-provider.react.js';
 import { qrCodeLinkURL } from 'lib/facts/links.js';
 import { useSecondaryDeviceLogIn } from 'lib/hooks/login-hooks.js';
 import { useQRAuth } from 'lib/hooks/qr-auth.js';
 import { generateKeyCommon } from 'lib/media/aes-crypto-utils-common.js';
-import * as AES from 'lib/media/aes-crypto-utils-common.js';
-import { hexToUintArray, uintArrayToHexString } from 'lib/media/data-utils.js';
+import { uintArrayToHexString } from 'lib/media/data-utils.js';
 import { useTunnelbroker } from 'lib/tunnelbroker/tunnelbroker-context.js';
-import {
-  peerToPeerMessageTypes,
-  type QRCodeAuthMessage,
-} from 'lib/types/tunnelbroker/peer-to-peer-message-types.js';
-import {
-  qrCodeAuthMessagePayloadValidator,
-  type QRCodeAuthMessagePayload,
-} from 'lib/types/tunnelbroker/qr-code-auth-message-types.js';
-import {
-  convertBytesToObj,
-  convertObjToBytes,
-} from 'lib/utils/conversion-utils.js';
 import { getContentSigningKey } from 'lib/utils/crypto-utils.js';
-import { getMessageForException } from 'lib/utils/errors.js';
 
 import css from './qr-code-login.css';
-import Alert from '../modals/alert.react.js';
-import VersionUnsupportedModal from '../modals/version-unsupported-modal.react.js';
 import {
-  base64DecodeBuffer,
-  base64EncodeBuffer,
-} from '../utils/base64-utils.js';
-
-async function composeTunnelbrokerMessage(
-  encryptionKey: string,
-  obj: QRCodeAuthMessagePayload,
-): Promise<QRCodeAuthMessage> {
-  const objBytes = convertObjToBytes(obj);
-  const keyBytes = hexToUintArray(encryptionKey);
-  const encryptedBytes = await AES.encryptCommon(crypto, keyBytes, objBytes);
-  const encryptedContent = base64EncodeBuffer(encryptedBytes);
-  return {
-    type: peerToPeerMessageTypes.QR_CODE_AUTH_MESSAGE,
-    encryptedContent,
-  };
-}
-
-async function parseTunnelbrokerMessage(
-  encryptionKey: string,
-  message: QRCodeAuthMessage,
-): Promise<?QRCodeAuthMessagePayload> {
-  const encryptedData = base64DecodeBuffer(message.encryptedContent);
-  const decryptedData = await AES.decryptCommon(
-    crypto,
-    hexToUintArray(encryptionKey),
-    new Uint8Array(encryptedData),
-  );
-  const payload = convertBytesToObj<QRCodeAuthMessagePayload>(decryptedData);
-  if (!qrCodeAuthMessagePayloadValidator.is(payload)) {
-    return null;
-  }
-
-  return payload;
-}
+  composeTunnelbrokerQRAuthMessage,
+  parseTunnelbrokerQRAuthMessage,
+  useHandleSecondaryDeviceRegistrationError,
+} from '../utils/qr-code-utils.js';
 
 function QRCodeLogin(): React.Node {
   const [qrData, setQRData] =
@@ -86,7 +38,7 @@
     }
   }, [setUnauthorizedDeviceID]);
 
-  const { pushModal } = useModalContext();
+  const handleError = useHandleSecondaryDeviceRegistrationError();
 
   const logInSecondaryDevice = useSecondaryDeviceLogIn();
   const performRegistration = React.useCallback(
@@ -94,20 +46,11 @@
       try {
         await logInSecondaryDevice(userID);
       } catch (err) {
-        console.error('Secondary device registration error:', err);
-        const messageForException = getMessageForException(err);
-        if (
-          messageForException === 'client_version_unsupported' ||
-          messageForException === 'unsupported_version'
-        ) {
-          pushModal(<VersionUnsupportedModal />);
-        } else {
-          pushModal(<Alert title="Unknown error">Uhh... try again?</Alert>);
-        }
+        handleError(err);
         void generateQRCode();
       }
     },
-    [logInSecondaryDevice, pushModal, generateQRCode],
+    [logInSecondaryDevice, handleError, generateQRCode],
   );
 
   React.useEffect(() => {
@@ -124,8 +67,8 @@
       secondaryDeviceID: qrData?.deviceID,
       aesKey: qrData?.aesKey,
       performSecondaryDeviceRegistration: performRegistration,
-      composeMessage: composeTunnelbrokerMessage,
-      processMessage: parseTunnelbrokerMessage,
+      composeMessage: composeTunnelbrokerQRAuthMessage,
+      processMessage: parseTunnelbrokerQRAuthMessage,
     }),
     [qrData, performRegistration],
   );
diff --git a/web/utils/qr-code-utils.js b/web/utils/qr-code-utils.js
new file mode 100644
--- /dev/null
+++ b/web/utils/qr-code-utils.js
@@ -0,0 +1,81 @@
+// @flow
+
+import * as React from 'react';
+
+import { useModalContext } from 'lib/components/modal-provider.react.js';
+import * as AES from 'lib/media/aes-crypto-utils-common.js';
+import { hexToUintArray } from 'lib/media/data-utils.js';
+import {
+  peerToPeerMessageTypes,
+  type QRCodeAuthMessage,
+} from 'lib/types/tunnelbroker/peer-to-peer-message-types.js';
+import {
+  qrCodeAuthMessagePayloadValidator,
+  type QRCodeAuthMessagePayload,
+} from 'lib/types/tunnelbroker/qr-code-auth-message-types.js';
+import {
+  convertBytesToObj,
+  convertObjToBytes,
+} from 'lib/utils/conversion-utils.js';
+import { getMessageForException } from 'lib/utils/errors.js';
+
+import { base64DecodeBuffer, base64EncodeBuffer } from './base64-utils.js';
+import Alert from '../modals/alert.react.js';
+import VersionUnsupportedModal from '../modals/version-unsupported-modal.react.js';
+
+async function composeTunnelbrokerQRAuthMessage(
+  encryptionKey: string,
+  obj: QRCodeAuthMessagePayload,
+): Promise<QRCodeAuthMessage> {
+  const objBytes = convertObjToBytes(obj);
+  const keyBytes = hexToUintArray(encryptionKey);
+  const encryptedBytes = await AES.encryptCommon(crypto, keyBytes, objBytes);
+  const encryptedContent = base64EncodeBuffer(encryptedBytes);
+  return {
+    type: peerToPeerMessageTypes.QR_CODE_AUTH_MESSAGE,
+    encryptedContent,
+  };
+}
+
+async function parseTunnelbrokerQRAuthMessage(
+  encryptionKey: string,
+  message: QRCodeAuthMessage,
+): Promise<?QRCodeAuthMessagePayload> {
+  const encryptedData = base64DecodeBuffer(message.encryptedContent);
+  const decryptedData = await AES.decryptCommon(
+    crypto,
+    hexToUintArray(encryptionKey),
+    new Uint8Array(encryptedData),
+  );
+  const payload = convertBytesToObj<QRCodeAuthMessagePayload>(decryptedData);
+  if (!qrCodeAuthMessagePayloadValidator.is(payload)) {
+    return null;
+  }
+
+  return payload;
+}
+
+function useHandleSecondaryDeviceRegistrationError(): (error: mixed) => void {
+  const { pushModal } = useModalContext();
+  return React.useCallback(
+    (error: mixed) => {
+      console.error('Secondary device registration error:', error);
+      const messageForException = getMessageForException(error);
+      if (
+        messageForException === 'client_version_unsupported' ||
+        messageForException === 'unsupported_version'
+      ) {
+        pushModal(<VersionUnsupportedModal />);
+      } else {
+        pushModal(<Alert title="Unknown error">Uhh... try again?</Alert>);
+      }
+    },
+    [pushModal],
+  );
+}
+
+export {
+  composeTunnelbrokerQRAuthMessage,
+  parseTunnelbrokerQRAuthMessage,
+  useHandleSecondaryDeviceRegistrationError,
+};