The best alternatives to Bounce Bar are Bites, IntroBar, and Abyssale. If these 3 options don't work for you, we've listed a few more alternatives below.
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Bites are cute ready-to-use popups with really clean html/css-code and free xd-sources. Choose any popup you like, set up the appearance trigger, animation speed and type, popup position and fade color in the css file. Then put popup code into your page and connectcss.