memory swap

you can upgrade RAM in a 27 inch iMac really easily. this video is for a 2014 model, but the steps are the same for 2014 to 2020 models.

you can find iMac memory from OWC here depending on the specific iMac you have.

if this is not what you wanted, read the article in BobTheFisherman's post above, then ask for what you meant to ask.

Please read this: Writing an effective Apple Support Commun… - Apple Community

then try asking again providing more detail, system information, and context.