A Deep Dive into Native Lazy-Loading for Images and Frames
CSS - Tricks
MAY 15, 2019
Make sure your servers support the HTTP Range: 0-2047 header and respond with status code 206 (Partial Content) to prevent them from delivering the full image twice. In the future, browsers might make twice as many image requests as there would be under the current proposal. First the range request, then the full request.
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