WeTransfer displays the true file size, which can appear smaller than what your computer shows. This is because your computer often displays the 'size on disk' rather than the actual file size.
Size on disk vs file size
The 'size on disk' is the amount of space a file occupies on your hard drive, which is typically larger than the file's actual size due to how storage is allocated. WeTransfer shows the true file size, not the size on disk — so the number may look smaller than what you see in your computer's file browser.
WeTransfer uses lossless compression, meaning your files are never altered or reduced in quality during the transfer process.
Rounding
You may also notice that file sizes are sometimes rounded up or down during upload or download. This is just a display choice — we show the closest whole number to keep things readable. No data is added or removed.