are google chrome extensions, open source or not? [duplicate]

This question already has answers here: Are all Google Chrome extensions open source by default? (7 answers) Closed 6 years ago.

I'm editing some extensions source codes, to create better or other extentions, some have a license file to tell you what you can do but many do not have, all i can see is a comment saying: all rights reserved by example.c开发者_运维技巧om so can i modify these extensions or not?

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Chrome extension source code can be viewed but it can still be under a copyright license. Need to ask the extension owner about the license details.

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Every Chrome Extension gives the user the following rights by default:

5.2 You grant to the user a non-exclusive, worldwide, and perpetual license to perform, display, and use the Products and any content contained in, accessed by, or transmitted through the Products in connection with Google Chrome. If you choose, you may include a separate end user license agreement (EULA) in your Product that will govern the user’s rights to the Products in lieu of the previous sentence.

Read the whole agreement here: http://developer.chrome.com/webstore/terms

Beyond that you will need to speak to the developer in question. Annoyingly the Google store does not display license terms for each Extension by default.