5 STEPS
1 The first step is to open the theme settings area of your Shopify theme config and go into the Recently viewed products section.
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2 Enable recently viewed products here.
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3 You can also set the title here.
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4 Slider will show your products in a rolling carousel slider.
Grid will show your products in rows.
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5 Displayed Recently viewed products.
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Here's an interactive tutorial for the visual learners
https://www.iorad.com/player/1602284/Demostore---Product-page-settings----Recently-Viewed-Products