In computer science, a modality is a methods in which humans interact with computers. There are 2 methods we are seeing shoppers buy through livestream sales.

The first and original modality was comment selling. By commenting “sold” along with a number or any other keyword, a shopper adds an item to their cart. They can comment for multiple items and then check out at the end of the sale. The main benefit of this method is the FOMO - the social proof that happens when other shoppers see the comments flowing in.

Comment selling also increases engagement and interactivity - comments make a live show entertaining. And shopping comments mixed with non-shopping comments makes the live feel less transactional and more like authentic engagement.

More comments also boosts the live in the Facebook algorithm. FB knows a user commented on a live before, and so that user is more likely to see the page’s future posts in their feed and get notified the next time they go live. A large number of comments also gives the live a higher reach to bring new viewers in on the action.

The second modality is the tap-to–buy method. Here the shopper just taps on an item to add it their cart. FB Shop, IG Shop, and TikTok Shop all follow this model.
This works well in an auction-like environment where’s there’s a single item for sale like in the Whatnot app.


The user just taps to bid and when the auction is over, the highest bidder won with a single tap. The simplicity of the UX matches the simplicity of an auction. The big advantage here is that the viewer never leaves the show to make the purchase.

This modality does not work so well in a non-auction environment where there are multiple products sold during the live, each product has its own set price with multiple pieces in inventory, and each product has variant options. This is a more complex environment. Some text is needed from the human for the computer to understand quantities, options, etc.

And the back-end management of limited inventory means cart holds and waitlists need to be created - something that FB Shop doesn’t support as it’s first-to-checkout that wins.

Each modality serves its own use case. If you're selling a single item in an auction-style environment or want a first-to-checkout-wins buying system, then go with FB Shop so that your shopper can just tap her way to checkout. If you want a first-to-comment-wins buying system, go with a commenting system like SoldLive or CommentSold.