Common Errors

Generation timeout

Cause: Your prompt describes a very complex extension, or the Extensy generation service is under high load.Fix: Simplify your prompt and break the extension into smaller features. Generate the core functionality first, then add features through refinement prompts. If the timeout persists across multiple attempts, reach out on the Extensy Discord for assistance.

Manifest file is missing or unreadable

Cause: You selected the wrong folder when clicking Load unpacked, or the ZIP was not fully extracted.Fix: Select the unzipped folder that directly contains manifest.json. If your unzipped folder contains another subfolder, open that inner folder and load it instead.

Permission errors in manifest

Cause: Your manifest.json requests permissions using Manifest V2 syntax, or includes permissions that are restricted under Manifest V3.Fix: Ensure all permissions use valid MV3 names (for example, use "scripting" instead of "tabs" for content script injection where possible). Remove any permissions your extension does not actively use.

{
  "manifest_version": 3,
  "permissions": ["storage", "activeTab", "scripting"]
}

Content Security Policy (CSP) violation

Cause: Manifest V3 prohibits inline scripts (JavaScript inside <script> tags in HTML) and the use of eval().Fix: Move all JavaScript into separate .js files and reference them with <script src="popup.js"></script>. Remove any eval() calls from your code.

<!-- Correct: external script reference -->
<script src="popup.js"></script>

<!-- Incorrect: inline script (blocked by MV3 CSP) -->
<script>document.getElementById('btn').onclick = () => {};</script>

Extension fails to load after unzipping

Cause: The ZIP was extracted into a nested folder structure, or manifest.json references files that are missing from the directory.Fix: After unzipping, confirm the folder structure matches what manifest.json expects. Every file referenced in the manifest (background script, popup, icons) must exist at the exact path listed.

Could not load background script

Cause: The path to your service worker in manifest.json does not match the actual filename on disk.Fix: Confirm the service_worker value in your manifest matches the exact filename in your extension folder, including case.

"background": {
  "service_worker": "background.js"
}

Extension context invalidated

Cause: You reloaded the extension in chrome://extensions, but the old content script is still running in an open tab.Fix: Refresh the webpage you’re testing. This restarts the content script with your updated extension code.

Cause: The action key in your manifest is missing default_popup, or the path points to a file that doesn’t exist.Fix: Add the correct popup path to your manifest and confirm the file exists in your extension folder.

"action": {
  "default_popup": "popup.html",
  "default_icon": "icons/icon48.png"
}

Unchecked runtime.lastError

Cause: An asynchronous Chrome API call (such as chrome.tabs.sendMessage) failed without an error handler.Fix: Add a chrome.runtime.lastError check in your callback, or wrap the call in a try/catch block.

chrome.tabs.sendMessage(tabId, { action: "ping" }, (response) => {
  if (chrome.runtime.lastError) {
    console.error(chrome.runtime.lastError.message);
    return;
  }
  console.log("Response:", response);
});

net::ERR_BLOCKED_BY_CLIENT

Cause: Another extension (such as an ad blocker) is conflicting with your extension or blocking its network requests.Fix: Disable other extensions temporarily, or test your extension in an Incognito window where other tools are turned off by default.

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