First version

The first version (M9470LL/A, model A1084) was introduced by Apple on July 7, 2004;^[6][7][8] it included an analog–optical audio mini-jack output, a USB port for remote printing or charging the iPod (iPod shuffle only), and one Ethernet port. The main processor of the 802.11g AirPort Express was a Broadcom BCM4712KFB wireless networking chipset, which incorporated a 200 MHz MIPS processor. The audio was handled by a Texas Instruments Burr-Brown PCM2705 16-bit digital-to-analog converter.

Updated version

An updated version (MB321LL/A, model A1264) supporting the faster 802.11 Draft-N draft specification and operation in either of the 2.4 GHz and 5 GHz bands, with almost all other features identical, was introduced by Apple in March 2008.^[9] The revised unit includes an 802.11a/n (5 GHz) mode, which allows adding Draft-N to an existing 802.11b/g network without disrupting existing connections, while preserving the increased throughput that Draft-N can provide.^[10] Up to 10 wireless units can connect to this AirPort Express.

The AirPort Express uses an audio connector that combines a 3.5 mm minijack socket and a mini-TOSLINK optical digital transmitter, allowing connection to an external digital-to-analog converter (DAC) or amplifier with internal DAC. Standard audio CDs ripped in iTunes into Apple Lossless format streamed to the AirPort Express will output a bit-for-bit identical bitstream when compared to the original CD (provided any sound enhancement settings in iTunes are disabled). DTS-encoded CDs ripped to Apple Lossless audio files - which decode as digital white noise in iTunes - will play back correctly when the AirPort Express is connected via TOSLINK to a DTS-compatible amplifier–decoder.^[11] This is limited to 16-bit and 44.1 kHz when streaming from iTunes; any higher quality content, such as high fidelity audio that uses up to 24-bit and/or 192 kHz will be truncated down to 16-bit and 44.1 kHz.^{[12][full citation needed]}

The audio output feature of the AirPort Express on a system running OS X Lion or earlier can only be used to wirelessly stream audio files from within iTunes to an attached stereo system. It cannot be used to output the soundtrack of iTunes video content to an attached stereo.^[13] OS X Mountain Lion introduced AirPlay support, a feature to output Mac system-wide audio directly to AirPort Express.^[14] This allows output of the audio of protected video content within iTunes, and also correctly maintains the audio sync with the image displayed on-screen. Video is synced with output audio when playing the video through an AirPort Express if the video is in a format supported by QuickTime Player (such as HTML 5 video in Safari etc.).

For Windows and Mac operating systems (before OS X Mountain Lion) there are a few software options available for streaming system-wide audio to the AirPort Express, such as Airfoil and TuneBlade. For the Logitech Media Server (Squeezeserver), the Airplay bridge plugin allows it to behave as a seamless squeezeplayer client

On August 28, 2018 Apple added AirPlay 2 support to the 2012 AirPort Express, providing the ability to be added to the Apple Home app as an audio destination.^[15]