Is it possible to upgrade the iMac 21.5 late 2013?

Be sure to let this part of the Apple info Fox Fifth posted soak in:

 Before you schedule an appointment, confirm that the specific Apple Authorized Service Provider offers memory upgrade services.

That means some Apple Authorized Service Providers will not add RAM to a 2012 through 2019 21.5-inch iMac. It requires almost a complete gutting of the computer to reach the nearly-hidden RAM slots and that comes with high risk of damage. Because of that, and the high labor costs they have to charge customers, several providers have told me they turn those jobs away. One I visited who will do the upgrade said he has the charge a minimum of two hour labor at US$75/hour to access the RAM slots. That is on top of the cost of the RAM and the resealing kit.

Plus adding RAM will not make the computer "feel" any faster. It is slow storage (mech hard drive), not a lack of RAM, that causes about 95% of the slow 2012-2019 21.5-inch iMac complaints we see here. Our 2011 entry-level iMac with the base mechanical storage tests ~30% faster in transfer to/from storage than the next-generation 21.5's.

Outside of getting a new computer, your only cost-effective option for a noticeable speed increase in your current computer, requiring neither pro help nor opening the computer, is to set up an external SSD as the boot volume. That can make your storage 6-8X faster if you currently have the base mechanical hard drive, and cost less that US$100. See:

Use an external SSD as your startup disk … - Apple Community

Just some food for thought:

1 - I wouldn't replace the hard drive but get an external SSD drive, clone your internal boot drive to it with Carbon Copy Cloner. This user tip describes how: Using Carbon Copy Cloner to Make a Bootable Clone of Intel Mac.

This will make the biggest change in your iMac's performance, i.e. decreased boot time and faster application launch time - not the increased RAM. If you go this route I recommend you contact Customer Support at OWC (MacSales.com) to see which of their units would best fit your iMac model, workflow and budget. You can probably increase the read and write time by at least 10x or more over what you have in there now.

OWC is considered the premier hardware supplier for Macs by most of the experienced contributors here. And you can take the drive with you when you upgrade the iMac in the future.

2 - I'd wait on the RAM increase to see if you'll need it. You might not need to endure the cost of having an Apple Authorized Service Provider do the upgrade.   This model can utilize up to 16 GB of RAM, i.e. adding another pair of 4 GB modules.

Upggrading the processor will be an impossible task, the I5 for the I7. The RAM is also non removable on this model (only the late 2013 27 inch has upgradable ram) the SSD will be a different exercition but it will be possible

I hope this helps for you!

Both the memory and drive can be upgraded. OWC is a well regarded source. Note that they rate the skill level needed for the upgraded as "Advanced" and recommend professional installation and that you contact their customer support.

See:

https://eshop.macsales.com/shop/memory/iMac/2012_21.5/DDR3L

and

https://eshop.macsales.com/installvideos/imac_21inch_mid2014_late2015/?filter=ssd

and see the following for install videos:

https://eshop.macsales.com/installvideos/imac_21inch_late_2013/?filter=memory

Also see the following from Install memory in an iMac - Apple Support

Memory is not removable by users on iMac (21.5-inch, Late 2012), iMac (21.5-inch, Late 2013), iMac (21.5-inch, Mid 2014), iMac (21.5-inch, 2017), iMac (Retina 4K, 21.5-inch, 2017), and iMac (Retina 4K, 21.5-inch, 2019). If the memory in one of these computers needs repair service, contact an Apple Retail Store or Apple Authorized Service Provider. If you’d like to upgrade the memory in one of these models, an Apple Authorized Service Provider can help. Before you schedule an appointment, confirm that the specific Apple Authorized Service Provider offers memory upgrade services.

shir0_zer0 wrote:

So the thing is this iMac does not get any updates anymore.

Catalina is the end of the line.

That's enough to run the current versions of Firefox, LibreOffice, and the commercial Affinity V2 applications … but for vendors like Microsoft and Adobe whose policy is to support only "the most recent three", Catalina's ship sailed a while ago.

If you wanted to upgrade the hard drive to a SSD, I would strongly recommend buying an external USB 3.* SSD, cloning your system onto it, ,and then setting it as your startup disk. No point in putting lots of money into the labor charges to upgrade the internal drive, when for $100 USD or less, you could have a SSD that requires no surgery (and can be easily reused with your next Mac).

Old Toad wrote:

2 - I'd wait on the RAM increase to see if you'll need it. You might not need to endure the cost of having an Apple Authorized Service Provider do the upgrade.   This model can utilize up to 16 GB of RAM, i.e. adding another pair of 4 GB modules.

It can take 16 GB of RAM – but not like that This is a 21.5" iMac with two sealed-in RAM sockets.

If Apple shipped the 8 GB of RAM in the form of two 4 GB modules, the only way to upgrade to 16 GB will be to remove all of the existing RAM, and then to install a pair of 8 GB modules.

While possible, it is not practical for several reasons.

It will not allow for a later macOS upgrade or Security update.

Those upgrades will cost 3 or 4 times more than the 2013 iMac is worth.

You can buy a new faster iMac or Mac mini and external display for just a few more $s.

I agree that DIY is fairly cheap, but that also hinges on whether or not you can pull it off without damaging something else like the logic board or display.

The question you have to ask yourself is, is it worth it to spend anything on it or is it better to wipe it and repurpose or resale as is...?

👍