Do you need the receiver for the DJI Mic 2 or Mic Mini?

You don't need the receiver if you record on a phone over Bluetooth or on a DJI Osmo Pocket 3, Osmo Action 4, Osmo Action 5 Pro or Osmo 360, because the transmitters connect to those directly. A Mic 2 transmitter can also record on its own to internal storage. You do need the receiver for regular cameras (Sony, Canon, Fujifilm and others), for a computer, for two people on a phone, and for the most reliable phone connection.

What works with a transmitter only

Device	Mic 2 TX	Mic Mini TX
Phone (Bluetooth)	One transmitter	One transmitter
Osmo Pocket 3	Up to two	Up to two
Osmo Action 4	One	One
Osmo Action 5 Pro	Listed as compatible	Up to two
Osmo 360	Listed as compatible	Listed as compatible
Standalone recording	Yes, 8 GB internal	No storage
Camera mic jack	No	No

From DJI's Mic 2 and Mic Mini FAQs. DJI sells single transmitters of both models for people who only need this.

Phones without the receiver

Pair one transmitter in your phone's Bluetooth settings. Tradeoffs:

Mic 2: no noise cancelling and no internal recording while connected to a phone.
Mic Mini: noise cancelling is fixed at Strong, and you can't change low cut in DJI Mimo.
Not every app accepts Bluetooth mics. DJI recommends testing your app first, for example with Bluetooth earbuds.
Only one person, since only one transmitter connects.

See Mic 2 Bluetooth and Mic Mini Bluetooth.

DJI Osmo cameras without the receiver

On the Osmo Pocket 3, Action 4 or Action 5 Pro, open the camera's settings, tap Wireless Microphone, and follow the steps. Audio settings for the transmitter appear in the camera, and the transmitter's link button can start and stop recording. See Mic 2 with Osmo Pocket 3 and Mic with action cameras.

Mic 2 as a standalone recorder

Power on a Mic 2 transmitter and press record. It saves 48 kHz WAV files (24-bit or 32-bit float) to its 8 GB of storage, about 14 hours at 24-bit. Sync it with your video later. The Mic Mini can't do this. See Mic 2 internal recording.

When you need the receiver

Any camera with a 3.5 mm mic input, or Sony cameras through DJI's hot-shoe camera adapter.
Two people on a phone, with each voice on its own channel in Stereo mode.
A computer, via the receiver's USB-C port.
Monitoring with headphones (Mic 2 receiver).
Best range: the receiver link is rated to 250 m FCC (Mic 2) and 400 m (Mic Mini).

DJI Mic Series Mobile Receiver

DJI also makes a tiny Mobile Receiver that plugs into a phone's USB-C port and accepts up to two transmitters, including mixed Mic Mini and Mic 2 pairs. It works with phones, computers and DJI Osmo cameras, but has no 3.5 mm camera output. See how many DJI mics per receiver.