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The Z-Index is an important property of CSS. The z-index property specifies the stack order of an element and its descendants. When elements overlap, z-order determines which one covers the other. When the element is placed on the top, it will not show whether you give it the index of 1000000. The tool is available under the console in Chrome Dev tools. It is more beneficial to frontend developers as this tool work with the frontend stuff, but it always helps to have the knowledge about what tools are your front-end developers friend using.