Cannot load extension with file or directory name _metadata. Filenames starting with "_" are reserved for use by the system.

[Gock Ge]

I am a developer of a extension. I updated the extension yesterday. 
When I download the extension, I have the following error:

"Cannot load extension with file or directory name _metadata. Filenames starting with "_" are reserved for use by the system."

My extension doesn't have filenames starting with "_".

Chrome version:  30.0.1599.114

OS: Ubuntu

The latest 34+ doesn't have this problem.

I doubt that it was caused by something changed in Chrome Store, maybe packaging app step. Because I remember the last version I submitted about a week ago has no problem. Yesterday I submitted a new version and tested on the same machine then it went wrong.

As i was searching for help, I found that same problem bothered other extensions and users as well, just from recently.  For examples: 

http://support.getadblock.com/discussions/problems/9263-cannot-install-adblock-2634-error-cannot-load-extension-with-file-or-directory-name-_-filenames-starting-with-_-are-reserved-for-use-by-the-system .

https://code.google.com/p/chromium/issues/detail?id=329557

[Ng Yik Phang]

Unfortunately, this is a Chrome Web Store bug/feature :(

If you download your CRX extension through manual methods, you will notice that the Chrome Web Store is adding an extra "_metadata" folder.

This is to be used for integrity/tamper protection by corruption/malware:

https://code.google.com/p/chromium/issues/detail?id=369895

Unfortunately, Chrome has an annoying "feature" that you cannot have file/folder names with an underscore in the front in your extension files, or else the extension won't run.

https://src.chromium.org/viewvc/chrome/trunk/src/extensions/common/file_util.cc#l252

But old versions of Chrome don't know about "_metadata" :(

I really hope the Chrome Web Store can detect the user agent and serve the "_metadata" folder only to new versions of Chrome, or change Chrome's code so that it doesn't rely on "_metadata"

This is a big headache for extension developers that are willing to support older versions of Chrome/Chrome forks. If the Chrome Web Store only wants to support the latest Chrome versions, then there's almost no point for the 'minimum_chrome_version' manifest field anyway.

[Gock Ge]

Thank you very much for your explanation. It is detailed and professional. Is there a way to to inform Chrome team of this bug? Have people discussed it in somewhere? Sorry I'm really a newbie in Chrome community and don't know what to do.

在 2014年5月23日星期五UTC+8下午10时32分02秒，Ng Yik Phang写道：

[Vara Kumar]

Already issues create about this problem. You can vote for these issues to get email notifications.

http://code.google.com/p/chromium/issues/detail?id=376713

http://code.google.com/p/chromium/issues/detail?id=377278