diff --git a/src-main/l10n/en.json b/src-main/l10n/en.json
index f4a79b20..6501acde 100644
--- a/src-main/l10n/en.json
+++ b/src-main/l10n/en.json
@@ -283,6 +283,10 @@
     "string": "Finalizing...",
     "developer_comment": "Status message that appears while finishing an update."
   },
+  "migrate.delete-legacy": {
+    "string": "Deleting old data...",
+    "developer_comment": "Status message that appears while finishing an update. Old data refers to data stored by old versions of the app that is now redundant after updates."
+  },
   "update.window-title": {
     "string": "Update Available",
     "developer_comment": "Title of update available window"
diff --git a/src-main/windows/migrate.js b/src-main/windows/migrate.js
index 5754b253..dcbac3de 100644
--- a/src-main/windows/migrate.js
+++ b/src-main/windows/migrate.js
@@ -8,19 +8,22 @@ const {APP_NAME} = require('../brand');
 const EMAIL = 'contact@turbowarp.org';
 
 class MigrateWindow extends BaseWindow {
-  static LATEST_VERSION = 2;
+  static LATEST_VERSION = 3;
 
   constructor () {
     super();
 
+    const oldDataVersion = settings.dataVersion;
+
     this.promise = new Promise((resolve) => {
       this.resolveCallback = resolve;
     });
 
     const ipc = this.window.webContents.ipc;
 
-    ipc.on('get-strings', (event) => {
+    ipc.on('get-info', (event) => {
       event.returnValue = {
+        oldDataVersion,
         locale: getLocale(),
         strings: getStrings()
       };
diff --git a/src-preload/migrate.js b/src-preload/migrate.js
index cd361c96..45f7e8e3 100644
--- a/src-preload/migrate.js
+++ b/src-preload/migrate.js
@@ -1,7 +1,7 @@
 const {contextBridge, ipcRenderer} = require('electron');
 
 contextBridge.exposeInMainWorld('MigratePreload', {
-  getStrings: () => ipcRenderer.sendSync('get-strings'),
+  getInfo: () => ipcRenderer.sendSync('get-info'),
   done: () => ipcRenderer.invoke('done'),
   continueAnyways: () => ipcRenderer.invoke('continue-anyways')
 });
diff --git a/src-renderer/migrate/migrate.html b/src-renderer/migrate/migrate.html
index 00e7e715..d4aa259b 100644
--- a/src-renderer/migrate/migrate.html
+++ b/src-renderer/migrate/migrate.html
@@ -152,7 +152,7 @@ <h1 class="title"></h1>
       TW_AutoSave -> abandon (likely to be very large)
       */
 
-      const {strings, locale} = MigratePreload.getStrings();
+      const {oldDataVersion, strings, locale} = MigratePreload.getInfo();
       document.documentElement.lang = locale;
 
       document.querySelector('.title').textContent = strings['migrate.title'];
@@ -360,6 +360,31 @@ <h1 class="title"></h1>
         });
       };
 
+      const deleteDatabase = (databaseName) => new Promise((resolve, reject) => {
+        const request = indexedDB.deleteDatabase(databaseName);
+        request.onerror = () => {
+          reject(new Error(`Failed to delete IDB database ${databaseName}: ${request.error}`));
+        };
+        request.onsuccess = () => {
+          resolve();
+        };
+      });
+
+      const deleteLegacyData = async () => {
+        localStorage.clear();
+        sessionStorage.clear();
+
+        for (let i = 0; i < databases.length; i++) {
+          await deleteDatabase(databases[i].name);
+
+          // i starts from 0, so add 1 for the database we just deleted
+          setStepProgress(i + 1, databases.length);
+
+          // Give the browser some time to clean up; deleting large databases might be intensive
+          await new Promise((resolve) => setTimeout(resolve, 250))
+        }
+      };
+
       const finish = async () => {
         await MigratePreload.done();
       };
@@ -423,13 +448,18 @@ <h1 class="title"></h1>
 
         await runStep(strings['migrate.preparing'], gatherMetadata);
 
-        if (!anyError) {
-          // Preparing must succeed for both of these, but each of these can fail
-          // independently.
+        if (!anyError && oldDataVersion < 2) {
+          // V2: Migrate data from file:// to tw-*://
+          // Preparing must succeed for both of these, but each can fail independently.
           await runStep(strings['migrate.transfer-editor'], migrateEditor);
           await runStep(strings['migrate.transfer-packager'], migratePackager);
         }
 
+        if (!anyError && oldDataVersion < 3) {
+          // V3: Removing leftover data on file://
+          await runStep(strings['migrate.delete-legacy'], deleteLegacyData);
+        }
+
         if (!anyError) {
           await runStep(strings['migrate.finalizing'], finish);
         }