Recently, while developing the Firefox OneNav extension, Xiaoz attempted manual installation of add-ons for debugging. However, an error occurred: "This add-on could not be installed because it has not been verified." Following guidance from ChatGPT, the issue was resolved.

![8dde04633731b5e8.png](https://img.rss.ink/imgs/2024/03/10/8dde04633731b5e8.png)

### Cause

Since Firefox version 48, Mozilla requires all extensions to undergo their validation and be signed for user safety. Unsigned extensions cannot be installed in standard and beta versions, a security measure against malicious extensions.

### Solution

**Method 1: Install via [Firefox Add-ons](https://addons.mozilla.org/zh-CN/firefox/)**

Extensions on Firefox Add-ons are signed after review, avoiding the "not verified" error.

![df789e9d31571d40.png](https://img.rss.ink/imgs/2024/03/10/df789e9d31571d40.png)

**Method 2: Use Developer Edition or Nightly**

Install "Firefox Developer Edition" or "Firefox Nightly" as the `xpinstall.signatures.required` parameter is effective only for these versions, not stable or beta versions.

> Firefox download link: [https://www.mozilla.org/en-US/firefox/channel/desktop/](https://www.mozilla.org/en-US/firefox/channel/desktop/)

![bf68cded7f46528c.png](https://img.rss.ink/imgs/2024/03/10/bf68cded7f46528c.png)

Developer Edition offers stable tools for developers, while Nightly showcases the latest developments but with lower stability for testing cutting-edge browser features.

After installation, input `about:config` in the Firefox address bar, agree to enable advanced options.

![6fe6e77c1af11e14.png](https://img.rss.ink/imgs/2024/03/10/6fe6e77c1af11e14.png)

Modify `xpinstall.signatures.required` to `false`, then restart the browser.

![153835cf07c73164.png](https://img.rss.ink/imgs/2024/03/10/153835cf07c73164.png)

Finally, on the add-ons page `about:addons`, install `.zip` or `.xpi` add-ons from file to avoid the mentioned error.

![460c59a48dd4719e.png](https://img.rss.ink/imgs/2024/03/10/460c59a48dd4719e.png)

### Conclusion

For regular users, it's recommended to use Method 1 via [Firefox Add-ons](https://addons.mozilla.org/zh-CN/firefox/). Developers are advised to install Firefox Developer Edition or Nightly and adjust parameters to resolve the issue.