Does the Samsung Galaxy S21 support eSIM?
Yes — with one caveat
US models of the S21 series do not support eSIM. Units sold in mainland China ship without eSIM support. The same model bought elsewhere has it.
The Samsung Galaxy S21 (2021) has eSIM hardware. That is a statement about the model, not about your specific unit — regional variants and carrier locks both change the answer, so confirm on the device before you buy a plan.
Check your actual handset in ten seconds
Dial *#06#
Open the phone dialler and enter it. If an EID appears alongside the IMEI, your unit has an eSIM. No EID means no eSIM, whatever the spec sheet says about the model.
Or check settings
iPhone: Settings → Mobile Service → Add eSIM. Android: Settings → Network & internet → SIMs → Add. If the option is missing, the device does not support it.
Carrier locks block it
A locked handset can have the hardware and still refuse a second profile. The lock is the blocker, not the chip — ask your carrier to unlock it before travelling.
Next step
Once you have confirmed the EID, pick a destination and compare what a gigabyte actually costs there.