16 delegations performed in the first semi-final of Eurovision 2021, 15 live and one in Australia, with a pre-recorded performance due to not being able to travel to Rotterdam due to Coronavirus travel restrictions.
Only 10 countries could advance to the Grand Final on Saturday and those countries are as follows (In the order they were announced):
Norway
Norway will perform in the 2nd half of the grand final

Israel
Israel will perform in the 1st half of the grand final

Russia
Russia will perform in the 1st half of the grand final

Azerbaijan
Azerbaijan will perform in the 2nd half of the grand final

Malta
Malta will perform in the 1st half of the grand final

Lithuania
Lithuania will perform in the 2nd half of the grand final

Cyprus
Cyprus will perform in the 1st half of the grand final

Sweden
Sweden will perform in the 2nd half on the grand final

Belgium
Belgium will perform in the 1st half of the grand final

Ukraine
Ukraine will perform in the 2nd half of the grand final

Here is the official confirmation of the countries who went through tonight on Twitter:
Unfortunately that means Slovenia, Australia, North Macedonia, Ireland, Croatia and Romania did not qualify for the Grand Final.
Here is the reaction at the post show press conference:
Semi Final 2 is on Thursday 20th May at 21:00 CET