This (Firefox) add-on (WebExtension) gives you a modern emoji picker that you can use to find and select emojis (i.e. the emoticons/smileys you know from messengers such as 😃, 😎 or 🤪). It will be directly copied to your clipboard and/or inserted into the active input on the page, when you choose it.

You can then use the emojis on almost any web page, including your favorite messenger (such as WhatsApp, Telegram, Threema, Signal, Wire etc.), social media (Facebook, Instagram, Twitter, Mastodon etc.) and even e-mails.

It will remember your recently used emojis across sites, and may often be faster than the emoji picker on the site itself.