You can send up to 4GB at once on the website.
To send bigger files, try using Desktop version or the Chrome extension.
When sending files using the 6-digit key, you can send without the limit on the file size. Using the Share Link, you can send files up to 20GB at once.
If you’re using Chrome browser, try out the Chrome Extension! You can send up to 10GB at once without installing any app on the PC.