The computer was designed around the need to cool its PowerPC 970 processor, and features an interior divided into zones for cooler, quieter operation.

An L-shaped aluminum foot elevates the display off the resting surface and allows the screen to be tilted from between –5 to 25 degrees, though it does not offer height adjustment or side-to-side swiveling.

On the back of the machine is a single row of input/output ports: analog input and analog/digital outport, Universal Serial Bus (USB), FireWire, a dial-up modem, and ethernet.

[3][a] The iMac features speakers powered by a 12-watt amplifier, positioned at the bottom of the machine so that sound is reflected off the resting surface towards the user.

The Serial AT Attachment (SATA) hard drives and random-access memory (RAM) of the iMac were the same as the contemporaneous Power Mac G5.

"By doing the three different cooling areas, we take a big heating challenge and break it into smaller ones, which is really the essence of good thermal design," Joswiak said.

[12] The company sought to allay concerns that the success of the iPod was to the detriment of the Mac division; "I really hope that when they see this iMac that it shows that it's not the case," Apple executive Phil Schiller told analysts.

[7] Exclusively for the education market, Apple offered a cheaper model with a worse graphics chipset and smaller hard drive.

The Wall Street Journal's Walt Mossberg and The Detroit Free Press's Mike Wendland called the iMac the best computer they had ever used.

[26] The New York Times's David Pogue suggested that the design of the iMac G5 was so similar to the iPod to visually entice buyers of the latter to try the all-in-one.

[27] The design was often called conservative or predictable compared to its predecessors,[26][27] although Wired considered the G5's simplicity an improvement over the "freakish and odd" G4.

[28] Mossberg noted that while Apple was not the first all-in-one computer to sit behind an LCD, it was thinner and more attractive than the competition.

[5] Mossberg noted that despite the stereotype that Macs were more expensive than Windows PCs, the iMac was comparably priced to the competition.

[30] Other complaints included the low amount of standard memory,[31][7][24] and the lack of forward-facing ports so that peripherals could be more easily connected.

[33] Early iMacs suffered from capacitors failing due to heat and faulty power supplies, which would result in Apple offering a repair program for the machines.