5 Ways to Transfer Files Between Devices Without Internet

USB: The Protocol Stack Nobody Thinks About

A USB cable is the most common offline option, and it does more behind the scenes than most people expect.

A phone plugged into a computer does not show up as a plain disk. It presents itself as a PTP (Picture Transfer Protocol) or MTP (Media Transfer Protocol) device. PTP was designed for digital cameras. MTP is Microsoft's extension of it and handles any file type. Both let the phone keep control of its own storage while the computer browses it.

An iPhone on Windows exposes only its camera roll, the DCIM folder. You can copy photos and videos off it and nothing else. Copying files onto the iPhone, or reaching files that belong to apps, needs the Apple Devices app or iTunes.

Android uses MTP and exposes most of its shared storage. Plug the phone in, tap the USB notification, choose File transfer, and it shows up in File Explorer. You can copy in both directions. Most Linux file managers speak MTP too.

Speed depends on the USB version the phone supports, not the shape of the connector. USB 2.0 is 480 Mbps on paper, roughly 30 to 40 MB/s in practice. USB 3 starts at 5 Gbps. Lightning iPhones run at USB 2.0 speed, and plenty of phones with a USB-C port do too, so check the spec sheet before you count on a fast cable. MTP also adds overhead per file, so a folder of thousands of small photos copies slower than one large video of the same total size.

The upside of USB is that it needs no network of any kind. The downsides: you need the right cable for both ends, and on an iPhone you only get photos unless you install Apple's software.

Local Wi-Fi Without a Router

Wi-Fi and internet access are separate things. Wi-Fi is a local radio link. The internet is whatever your router connects to upstream. Two devices on the same Wi-Fi network can exchange data when that upstream link is down or was never there.

There are two ways to get a shared network without a router.

Wi-Fi Direct. Two devices form a direct Wi-Fi link: one acts as a small access point and the other joins it. Android supports it natively, and Windows exposes it to apps. iPhones don't support standard Wi-Fi Direct. AirDrop uses Apple's own peer-to-peer Wi-Fi link instead.

A phone hotspot. Turn on the phone's hotspot and connect the computer to it. Both devices are now on the same local network, and traffic between them never leaves the room. Android lets you run a hotspot with mobile data turned off. On iPhone, Personal Hotspot generally needs cellular data switched on and a plan that includes hotspot use, but traffic between the phone and the computer is local and does not use your data. The computer may still send its own background traffic, such as updates, over the hotspot, so watch that if your plan is small.

Speed on a hotspot network is set by the phone's Wi-Fi radio, not its cellular signal. A weak cellular signal doesn't slow down a local transfer.

OpenDrop works on a hotspot network because its Wi-Fi mode only needs the phone and the computer on the same local network. The desktop app runs a local server (port 8000 by default) and announces itself over mDNS as _opendrop._tcp.local.. A phone that has paired with it by QR code finds it and streams files straight to it at full speed, with no chunking, on Free and Pro. Nothing goes through the internet.

HTTP Over a LAN (No Internet Required)

This is the most misunderstood option. HTTP is a protocol, not an internet service. One device can run an HTTP server and another device on the same network can talk to it. The data only travels as far as the router, switch or hotspot the two share.

The mechanism is simple. One device runs a web server on its local IP address and a port. The other sends requests to that address. To send a file, the client makes a POST request with the file as the body, and the server writes it to disk. The body is streamed, so a large file never has to fit in memory. Most LAN file sharing apps work this way, because every platform has solid HTTP libraries.

The hard part is discovery: how does the phone learn the computer's address? On most home and office networks, mDNS handles it. The server announces itself with multicast on UDP port 5353 and clients listen. Some networks block multicast. Guest Wi-Fi often goes further and blocks all traffic between devices (client isolation), and then no LAN method works. A phone hotspot gets around that.

OpenDrop handles the blocked-multicast case with its QR code. The code holds a private pairing key and the addresses your phone needs to reach your computer, plus a certificate fingerprint so the phone can check it is really your PC. The phone scans it and connects directly, with no discovery step.

A local network is not private by default, so OpenDrop adds two layers on top of HTTP. Requests between your devices are signed with HMAC-SHA256 using the secret your devices share when you pair them. File contents are encrypted with ChaCha20-Poly1305 on the sending device before they leave it, so other devices on the same Wi-Fi can't read the contents off the wire.

Bluetooth: The Slow Option That Needs No Network

Classic Bluetooth file transfer uses OBEX (Object Exchange), a protocol that started on infrared links in the 1990s for swapping things like contact cards. Most Android phones, Windows PCs and Linux desktops still support it. iPhones do not: iOS has no Bluetooth file transfer, and Apple routes sharing through AirDrop.

Speed is the catch. Classic Bluetooth with Enhanced Data Rate peaks at 3 Mbps on paper and about 2.1 Mbps of usable throughput, roughly 260 KB/s. Real transfers usually land below that. Bluetooth 5 doesn't change this for file transfer: its 2 Mbps mode belongs to Bluetooth Low Energy, which is built for small, low-power messages.

At 260 KB/s, a 1 GB file takes more than an hour. Wi-Fi is around two orders of magnitude faster for bulk data.

Pairing adds friction. Both devices need Bluetooth on and visible, you pick the target from a list, and you may have to confirm a code. On Windows you also have to open the Bluetooth file transfer window and choose Receive files before the other side sends.

Bluetooth makes sense for a contact, a small document or a single photo when there is nothing else: no Wi-Fi, no cable, no drive. Range is about 10 meters.

OpenDrop uses Bluetooth Low Energy in a narrower way. With Pro, two phones signed in to the same OpenDrop account can send files to each other over BLE when there is no Wi-Fi or internet, iPhone or Android. It's slower than Wi-Fi but needs no network, and file contents are still encrypted. Computers don't use Bluetooth in OpenDrop; they connect over Wi-Fi or the internet.

Physical Media: SD Cards, Flash Drives, and External SSDs

For a very large one-off copy, a drive carried between two machines is often the fastest link you have.

A good USB 3 flash drive reads at 100 MB/s or more, though cheap drives write far slower. A portable SSD on a 10 Gbps USB port can approach 1,000 MB/s. For 50 or 100 GB, such as a whole photo library, that beats any wireless option.

The workflow: copy to the drive on machine A, carry it over, copy off on machine B. Phones need an adapter (USB-C OTG, or Apple's Lightning to USB 3 Camera Adapter for older iPhones) and a file app. Most Android phones read USB drives in their Files app. iPhone and iPad have read external drives in the Files app since iOS 13. Format the drive as exFAT and it works on Windows, iPhone, most Android phones and current Linux distributions.

SD cards do the same job in a smaller package. Many laptops still have a card slot. Most phones dropped microSD, but a USB-C card reader covers that.

Physical media is also the only method here where the two machines never need to be connected, or even switched on at the same time. That is why air-gapped and security-sensitive setups rely on it.

Choosing Based on What You're Actually Transferring

Pick by file size, the hardware you have, and how often you do it.

A few small files (under 50 MB): Bluetooth works between Android phones and computers if you can wait. A cable is faster if you have one.

Medium transfers (50 MB to 5 GB): Local Wi-Fi is the best balance of speed and convenience. Use a phone hotspot if there's no router. OpenDrop or a similar tool handles the transfer over that local link.

Large transfers (5 GB+): A USB 3 cable or a portable SSD. Wi-Fi works too, but at this size raw throughput matters. The exception: if the phone only does USB 2.0, a strong Wi-Fi 5 or Wi-Fi 6 connection can beat the cable.

Regular recurring transfers: Install a local transfer tool and leave it set up. OpenDrop runs on Windows, Linux, iPhone, iPad and Android, with macOS coming soon. Free needs no account: pair your phone with your computer by scanning a QR code, then send files over whatever local network the two share, home Wi-Fi or a phone hotspot. With Pro, the phones, tablets and computers signed in to your account connect automatically, and two phones can use Bluetooth when there's no Wi-Fi.

None of these methods need the internet. For devices in the same room, most of them are also faster than uploading to a cloud service and downloading again.