A PC speaker is a loudspeaker built into some IBM PC compatible computers. The first IBM Personal Computer, model 5150, employed a standard 2.25 inch magnetic driven (dynamic) speaker. More recent computers use a tiny moving-iron or piezo speaker instead. The speaker allows software and firmware to provide auditory feedback to a user, such as to report a hardware fault. A PC speaker generates waveforms using the programmable interval timer, an Intel 8253 or 8254 chip.

The PC speaker is used during the power-on self-test (POST) sequence to indicate errors during the boot process. Since it is active before the graphics card, it can be used to communicate "beep codes" related to problems that prevent the much more complex initialization of the graphics card to take place. For example, the Video BIOS usually cannot activate a graphics card unless working RAM is present in the system while beeping the speaker is possible with just ROM and the CPU registers. Usually, different error codes will be signalled by specific beeping patterns, such as e.g. "one beep; pause; three beeps; pause; repeat". These patterns are specific to the BIOS/UEFI manufacturer and are usually documented in the technical manual of the motherboard.

Several programs, including music software, operating systems or games, could play pulse-code modulation (PCM) sound through the PC speaker using special Pulse-width Modulation techniques explained later in this article.

The PC speaker was often used in very innovative ways to create the impression of polyphonic music or sound effects within computer games of its era, such as the LucasArts series of adventure games from the mid-1980s, using swift arpeggios.^{[citation needed]} Several games such as Space Hulk and Pinball Fantasies were noted for their elaborate sound effects; Space Hulk, in particular, even had full speech.

However, because the method used to reproduce PCM was very sensitive to timing issues, these effects either caused noticeable sluggishness on slower PCs or sometimes failed on faster PCs (that is, significantly faster than the program was originally developed for). Also, it was difficult for programs to do much else, even update the display, during the playing of such sounds. Thus, when sound cards (which can output complex sounds independent from the CPU once initiated) became mainstream in the PC market after 1990, they quickly replaced the PC speaker as the preferred output device for sound effects. Most newly-released PC games stopped supporting the speaker during the second half of the 1990s.

Several programs, including MP (Module Player, 1989), Scream Tracker, Fast Tracker, Impulse Tracker, and even device drivers for Linux and Microsoft Windows, could play PCM sound through the PC speaker, though with marginal sound quality.

Modern Microsoft Windows systems have PC speaker support as a separate device with special capabilities – that is, it cannot be configured as a normal audio output device. Some software uses this special sound channel to produce sounds. For example, Skype can use it as a reserve calling signal device for the case where the primary audio output device cannot be heard (for example because the volume is set to the minimum level, the amplifier is turned off or headphones are plugged in).^{[citation needed]}

Linux kernel includes the "snd-pcsp.ko" driver module since 2008. Once the module is loaded, the PC speaker can be used as a normal sound card, allowing all programs (applications, graphical desktops, utilities, etc.) to play sounds and music through the PC speaker. By default, Linux kernel loads the "pcspkr.ko" module, that only emits beeps. To get full sounds and music through the PC speaker (and also beeps), you have to unload "pcspkr.ko" and load "snd-pcsp.ko":   modprobe -r pcspkr && modprobe snd-pcsp