How do you create google chrome extensions?

What are the best Google Chrome Extensions for Web Designers, also they should be Free and Easy to use?

• simply answer what free and easy to use extensions are present which are helpful for Web Developer and Web designer ? One link i found which mentioned some good name is : http://www.techieoasis.org/2013/08/top-10-best-google-chrome-extensions.html

• Answer:

  https://chrome.google.com/webstore/detail/window-resizer/kkelicaakdanhinjdeammmilcgefonfh - Quickly resize the browser window to various screen sizes, including mobile. Works great. https://chrome.google.com/webstore/detail/capture-webpage-screensho/mcbpblocgmgfnpjjppndjkmgjaogfceg - Takes screenshot and allows you to edit and then save in multiple formats. I tried a few out and this was the best for me. https://chrome.google.com/webstore/detail/ruul-screen-ruler/mlbnpnlmfngmlcmkhjpbfokdphfehhjj - A ruler that appears on screen. Kind of gimicky and slow. I use it to align stuff. Probably a better tool out there for it (hence I came to this Quora question) https://chrome.google.com/webstore/detail/google-font-previewer-for/engndlnldodigdjamndkplafgmkkencc - Haven't used it yet, but sounds extremely useful as a front-end developer. https://chrome.google.com/webstore/detail/eye-dropper/hmdcmlfkchdmnmnmheododdhjedfccka - sample colors from websites. It's slow, but gets the job done.