What is Underpass?
Underpass is a file transfer and chat app that features end-to-end encryption for complete privacy and security.

Communicate with another person or between your own devices.

Why Underpass?
Read the story of why I wrote Underpass and why you should use it.

What are the iOS system requirements?
iOS 10, 11, or 12 on iPhone, iPad, and iPod.

What are the macOS system requirements?
macOS 10.12 Sierra, 10.13 High Sierra, or 10.14 Mojave.

How do I get support?
For documentation and contact information, see Underpass Support.

Underpass Features:

• Peer-to-Peer — There's no signup or account. Underpass does not connect to a third-party service. Your Mac or iOS device makes a direct network connection to another Mac or iOS device.
• Privacy — Underpass does not request your phone number, email, contacts, or any other personal information. You don't even need to use your real name.
• Communicate over the internet or on a local area network (LAN).
• Encrypted file transfers!
• Inline images, including animated gifs.
• Full Unicode and emoji support.
• Industry-standard AES-128 encryption.

Screenshots:

Who is the developer?
Underpass was created by Jeff Johnson, an independent developer with over a decade of software engineering experience on Apple platforms. Jeff was a longtime engineer at Rogue Amoeba Software, working on apps such as Airfoil. Before that he was the lead engineer of Knox (originally developed by MK&C, later sold to AgileBits) and the lead engineer of the open source RSS reader Vienna.

Jeff is also the developer of the StopTheMadness Safari extension.