diff --git a/src/common/request.js b/src/common/request.js
index 5d3ed66..d7463b9 100644
--- a/src/common/request.js
+++ b/src/common/request.js
@@ -1,71 +1,90 @@
 const clampProgress = (n) => Math.max(0, Math.min(1, n));
 
-const request = ({
-  url,
-  type,
-  progressCallback,
-  timeout,
-  estimatedSize,
-  abortTarget
-}) => new Promise((resolve, reject) => {
-  const xhr = new XMLHttpRequest();
-  xhr.onload = () => {
-    cleanup();
-    if (xhr.status === 200) {
-      resolve(xhr.response);
-    } else {
-      reject(new Error(`Couldn't fetch ${url}: status code ${xhr.status}`));
-    }
-  };
-  xhr.onerror = () => {
-    cleanup();
-    reject(new Error(`Couldn't fetch ${url}, are you offline?`));
-  };
+const request = async (options) => {
+  const {
+    type,
+    progressCallback,
+    timeout,
+    estimatedSize,
+    abortTarget
+  } = options;
 
-  if (progressCallback) {
-    xhr.onprogress = (e) => {
-      if (e.lengthComputable) {
-        progressCallback(clampProgress(e.loaded / e.total));
-      } else if (estimatedSize) {
-        progressCallback(clampProgress(e.loaded / estimatedSize));
+  const requestURL = (url) => new Promise((resolve, reject) => {
+    const xhr = new XMLHttpRequest();
+    xhr.onload = () => {
+      cleanup();
+      if (xhr.status === 200) {
+        resolve(xhr.response);
+      } else {
+        reject(new Error(`Couldn't fetch ${url}: status code ${xhr.status}`));
       }
     };
-  }
-
-  xhr.responseType = type;
-  xhr.open('GET', url);
-  xhr.send();
-
-  const cleanup = () => {
-    if (cleanupAbortCallback) {
-      cleanupAbortCallback();
-    }
-    if (timeoutId) {
-      clearTimeout(timeoutId);
-    }
-  };
-
-  let cleanupAbortCallback;
-  if (abortTarget) {
-    const abortCallback = () => {
-      xhr.abort();
+    xhr.onerror = () => {
       cleanup();
-      reject(new Error(`Couldn't fetch ${url}: aborted`));
+      reject(new Error(`Couldn't fetch ${url}, are you offline?`));
     };
-    abortTarget.addEventListener('abort', abortCallback);
-    cleanupAbortCallback = () => {
-      abortTarget.removeEventListener('abort', abortCallback);
+  
+    if (progressCallback) {
+      xhr.onprogress = (e) => {
+        if (e.lengthComputable) {
+          progressCallback(clampProgress(e.loaded / e.total));
+        } else if (estimatedSize) {
+          progressCallback(clampProgress(e.loaded / estimatedSize));
+        }
+      };
+    }
+  
+    xhr.responseType = type;
+    xhr.open('GET', url);
+    xhr.send();
+  
+    const cleanup = () => {
+      if (cleanupAbortCallback) {
+        cleanupAbortCallback();
+      }
+      if (timeoutId) {
+        clearTimeout(timeoutId);
+      }
     };
-  }
+  
+    let cleanupAbortCallback;
+    if (abortTarget) {
+      const abortCallback = () => {
+        xhr.abort();
+        cleanup();
+        reject(new Error(`Couldn't fetch ${url}: aborted`));
+      };
+      abortTarget.addEventListener('abort', abortCallback);
+      cleanupAbortCallback = () => {
+        abortTarget.removeEventListener('abort', abortCallback);
+      };
+    }
+  
+    let timeoutId;
+    if (timeout) {
+      timeoutId = setTimeout(() => {
+        xhr.abort();
+        cleanup();
+        reject(new Error(`Couldn't fetch ${url}: timed out`));
+      }, timeout);
+    }
+  });
 
-  let timeoutId;
-  if (timeout) {
-    timeoutId = setTimeout(() => {
-      xhr.abort();
-      cleanup();
-      reject(new Error(`Couldn't fetch ${url}: timed out`));
-    }, timeout);
+  const urls = Array.isArray(options.url) ? options.url : [options.url];
+  if (urls.length === 0) {
+    throw new Error('no URLs');
   }
-});
+  let errorToThrow;
+  for (const url of urls) {
+    try {
+      return await requestURL(url);
+    } catch (e) {
+      if (!errorToThrow) {
+        errorToThrow = e;
+      }
+    }
+  }
+  throw errorToThrow;
+};
 
 export default request;
diff --git a/src/packager/large-assets.js b/src/packager/large-assets.js
index 70f627b..0de0bea 100644
--- a/src/packager/large-assets.js
+++ b/src/packager/large-assets.js
@@ -1,61 +1,72 @@
-const LARGE_ASSET_BASE = 'https://packagerdata.turbowarp.org/';
-const SCAFFOLDING_ROOT = 'scaffolding/';
+// This defines where files are fetched from when the packager needs to download files.
+// Files fetched from an external server have a SHA-256 checksum used to validate the download.
+// src is the URL that will be fetched to download the asset. If it's an array of URLs, each URL
+// will be tried in succession if the previous one fails, perhaps because it's blocked by a school
+// network filter.
+
+const externalFile = (name) => [
+  // Hopefully one of these URLs will not be blocked.
+  `https://packagerdata.turbowarp.org/${name}`,
+  `https://blobs.turbowarp.xyz/${name}`
+];
+
+const relativeScaffolding = (name) => `scaffolding/${name}`;
 
 export default {
   'nwjs-win64': {
-    src: LARGE_ASSET_BASE + 'nwjs-v0.54.0-win-x64.zip',
+    src: externalFile('nwjs-v0.54.0-win-x64.zip'),
     sha256: '0f082671b67b711f783d98cc989cf5aebacfc9bce3bef78875b57d08fc2a6e86',
     type: 'arraybuffer'
   },
   'nwjs-win32': {
-    src: LARGE_ASSET_BASE + 'nwjs-v0.54.0-win-ia32.zip',
+    src: externalFile('nwjs-v0.54.0-win-ia32.zip'),
     sha256: '7a1ed3a6a51b8cdf9280761b90cb4723cf9ee8050e3ed0b58451e8e4e694b203',
     type: 'arraybuffer'
   },
   'nwjs-mac': {
-    src: LARGE_ASSET_BASE + 'nwjs-v0.54.0-osx-x64.zip',
+    src: externalFile('nwjs-v0.54.0-osx-x64.zip'),
     sha256: '498c97a264f8feac504c4c2396c1fddc8290c15573aee2fc692e59ff9803cc40',
     type: 'arraybuffer'
   },
   'nwjs-linux-x64': {
-    src: LARGE_ASSET_BASE + 'nwjs-v0.54.0-linux-x64.zip',
+    src: externalFile('nwjs-v0.54.0-linux-x64.zip'),
     sha256: '53651a3a12d29ad096cff5b44d9f1e3aa09e9fad970bdcfe8bda07ea23d960d8',
     type: 'arraybuffer'
   },
   'electron-win32': {
-    src: LARGE_ASSET_BASE + 'electron-v15.0.0-win32-ia32.zip',
+    src: externalFile('electron-v15.0.0-win32-ia32.zip'),
     sha256: '5b69112b91010d78abf6012f387ea3fe5c0e36657c5f386a4c2bb42138aa1a8e',
     type: 'arraybuffer'
   },
   'electron-win64': {
-    src: LARGE_ASSET_BASE + 'electron-v15.0.0-win32-x64.zip',
+    src: externalFile('electron-v15.0.0-win32-x64.zip'),
     sha256: '3d95422d9f2fccb07b745b31007548231d80ff63e3640f49a5f8591498a3afa2',
     type: 'arraybuffer'
   },
   'electron-linux64': {
-    src: LARGE_ASSET_BASE + 'electron-v15.1.1-linux-x64.zip',
+    src: externalFile('electron-v15.1.1-linux-x64.zip'),
     sha256: '70de2da51c6a8591b88f08366c82166a51b1719243f67ef1a14eddbb806a115f',
     type: 'arraybuffer'
   },
   'webview-mac': {
-    src: LARGE_ASSET_BASE + 'WebView-macos-3.zip',
+    src: externalFile('WebView-macos-3.zip'),
     sha256: '5d4086894f10549c61c20e5f770c808afc25c2e4793da75b5b1cede294449fac',
     type: 'arraybuffer'
   },
   scaffolding: {
-    src: SCAFFOLDING_ROOT + 'scaffolding.js',
+    src: relativeScaffolding('scaffolding.js'),
     estimatedSize: 4775503,
     useBuildId: true,
     type: 'text'
   },
   'scaffolding-min': {
-    src: SCAFFOLDING_ROOT + 'scaffolding-min.js',
+    src: relativeScaffolding('scaffolding-min.js'),
     estimatedSize: 2540321,
     useBuildId: true,
     type: 'text'
   },
   addons: {
-    src: SCAFFOLDING_ROOT + 'addons.js',
+    src: relativeScaffolding('addons.js'),
     estimatedSize: 14339,
     useBuildId: true,
     type: 'text'
diff --git a/src/packager/web/cache.js b/src/packager/web/cache.js
index 4255f28..3a7d63c 100644
--- a/src/packager/web/cache.js
+++ b/src/packager/web/cache.js
@@ -9,7 +9,9 @@ const STORE_NAME = 'assets';
 const db = new Database(DATABASE_NAME, DATABASE_VERSION, STORE_NAME);
 
 const getAssetId = (asset) => {
-  return `${asset.src}-${asset.type}-${asset.sha256 || buildId}`;
+  const urls = asset.src;
+  const firstURL = Array.isArray(urls) ? urls[0] : urls;
+  return `${firstURL}-${asset.type}-${asset.sha256 || buildId}`;
 };
 
 const removeExtraneous = async () => {