Router/Access point: Matchbox, eg: TP-Link TL-WR802N (57 × 57 ×18 mm) [6] or GL-Inet GL-MT300N (58 x 58 x 25mm) [7]
WiFi USB Client: Fingernail, eg: Asus USB-AX56 adapter (25.5 x 16 x 9mm) [8]
WiFi Card Client: Postage stamp, eg: Intel Dual-Band Wireless Adapter AC-7260NGW M.2 2230 (22mm x 30mm x 2.4mm) [10]
802.11n Wireless N range: theoretically 230 ft (70 m) range indoors and 820 ft (250m) range outdoors, which is approximately 1 FIFA soccer field's (105 x 68 m) width for indoor range, and 2 soccer fields end-to-end by 3 side-to-side for outdoor range. Newer protocols do not seem to have extended the range of individual radios but rather rely on repeaters or range extender devices to provide additional coverage.
https://www.hummingbirdnetworks.com/articles/what-is-the-dis...
https://en.wikipedia.org/wiki/IEEE_802.11#Protocol
https://publications.fifa.com/de/football-stadiums-guideline...
Some of these are slightly older devices dating from around 2020, but the sizes should generally still be approximately the same in 2025.
Router/Access point: Mobile operating systems like WebOS, Android, and iOS have had hotspot capabilites built-in since around around 2010 (Mobile Hotspot on Palm Pre and Pixi Plus in 2010 [1], Wifi Tethering in Android 2.2 Froyo in 2010 [2], and Personal Hotspot in iOS 4.3 for iPhone 4 and 3GS in 2011 [3]). Today you can configure your phone to become a personal Wifi router with one button press [4], [5].
[1] https://www.cnn.com/2010/TECH/01/07/ces.palm.pre.plus.pixi/i...
https://web.archive.org/web/20101125023042/http://articles.c...
https://archive.is/UD1Dm
[2] https://www.wired.com/2010/05/android-22-froyo-features-usb-...
https://web.archive.org/web/20140707210122/https://www.wired...
https://archive.is/kjH1N
[3] https://www.engadget.com/2011-03-09-ios-4-3-spotlight-person...
https://web.archive.org/web/20251018061108/https://www.engad...
https://archive.is/QBRod
[4] https://support.google.com/android/answer/9059108?hl=en
[5] https://support.apple.com/guide/iphone/share-your-internet-c...
For a discrete router device, TP-Link TL-WR802N (57 × 57 ×18 mm) [6] and GL-Inet GL-MT300N (58 x 58 x 25mm) [7] are matchbox-sized travel router devices that fit into the palm of your hand, cost less than $30 USD, and consume less than 2.75W (they can be run from a basic 5V, 1A USB connection).
[6] https://www.tp-link.com/us/home-networking/wifi-router/tl-wr...
https://web.archive.org/web/20250724184720/https://www.tp-li...
[7] https://www.gl-inet.com/products/gl-mt300n-v2/
https://web.archive.org/web/20250822045920/https://www.gl-in...
Wifi Client: Wifi capabilities are now built into mobile phone, TV, and many camera chipsets, there is no separate card required. If you want a separate WiFi adapter, you can buy a USB adapter that is about the size of a fingernail or 5 small coins stacked together (eg: 5 US pennies, or 5 Euro 1-cent coins), basically take the metal part of a USB-A male connector and extend or extrude it a bit. This Asus USB-AX56 adapter [8] is 25.5 x 16 x 9mm and supports WiFi 6 (802.11ax) with theoretical speeds up to 9.6 Gbps (actual real-world speeds appear closer to 800 Mbps). Streams in Wifi 6 can be up to 160MHz wide via channel bonding of up to 8 adjacent 20 MHz channels, but in practice this is only feasible in locations with low or no interference. Note that wider channels have a reduced effective range and perform poorly at a distance or through obstructions.
[8] https://www.asus.com/networking-iot-servers/adapters/all-ser...
https://web.archive.org/web/20251018061524/https://www.asus....
https://www.wi-fi.org/wi-fi-macphy
Discrete Wifi cards can still be found in some laptop computers (although many Wifi cards are now soldered down), one of the more recent (introduced around 2013 to 2015) and smaller sizes is M.2 2230 (22mm x 30mm x 2.4mm) which is also the form factor for some M.2 PCI-Express SSDs (solid state storage drives, typically flash devices). These are about the size of a postage stamp, weigh around 2.3 grams, and cost around $20 USD or less.
One example is Intel AX210 [9] which supports Wi-Fi 6E, on 3 bands: 2.4 / 5 / 6GHz in a 2x2 configuration (2 TX transmit and 2 RX receive antennas) at speeds of 2.4 Gbps, and also features Bluetooth 5.3.
[9] https://www.intel.com/content/www/us/en/products/sku/204836/...
A popular previous-generation device is Intel Dual-Band Wireless Adapter AC-7260NGW [10] with good support for GNU/Linux, again with a M.2 2230 (22mm x 30mm x 2.4mm) form-factor approximately the size of a postage stamp, supporting Wifi 5 802.11ac with up to 867 Mbps theoretical bandwidth on dual bands in a 2x2 configuration (2 TX transmit and 2 RX receive radios), and 433 Mbps per stream. Channels can be up to 80MHz wide via channel bonding of 4 adjacent 20 MHz channels.
An alternative, earlier form factor was Half Mini-PCI-Express, for example Intel Dual-Band Wirelss Adapter AC-7260HMW [10] at 26.80 x 30 x 2.4 mm.
[10] https://www.mouser.com/datasheet/2/612/dual-band-wireless-ac...
https://web.archive.org/web/20251018061520/https://www.mouse...