Google has added an emoji and GIF discovery feature to Allo on the web, allowing users to more easily find the perfect emoji or GIF to insert into a message along with any context you may have already typed up. Google began this update yesterday and it should already be live for everyone, so if you're already using the Allo web client, then the next time you open it up you'll see a popup message highlighting the new feature as soon as you open one of your existing chats.
The new feature is accompanied by the Smart Smiley button, which will show you relevant emoji, GIFs, and stickers to insert into messages. The reason these are going to be "relevant" is because the stickers, GIFs, or emoji you see in the popup bar will change based on what you're typing. So for example, asking someone if you're still going to meet up for dinner, will shift the stickers and other things that are visible to food-related options, like in the image below. This is the smart part of it, as you won't have to go digging around to find the sticker you want. If you know you're going to be inserting a sticker, GIF, or emoji into your chats, hit the Smart Smiley button beforehand and then begin to type as this will sniff out and find you the perfect pairings.
The visual appearance is just like in the Android app so it should look familiar if you've already used this feature and button in the app before, and of course it also works in the same way. Stickers and emoji, including animated emoji, will automatically be shown in the bar above the text entry field, but to see the GIFs in this same bar, you need to hit a little arrow button to the right of the last sticker or emoji, which when clicked a few times will present you with a GIF search button. Click that and it will populate any related GIFs that should have something to do with what you typed. This seems to be the only change for the Allo web client, but it's a big feature add if you're big on using GIFs, stickers, and emoji in your chats.