5 Ways to Transfer Files Between Devices Without Internet

USB: The Protocol Stack Nobody Thinks About

Plugging a USB cable between a phone and a computer is the most common offline transfer method. Most people think of it as simple. It's not, technically, but the complexity is hidden well.

When you connect an iPhone to a Windows PC via USB, the phone presents itself as a PTP (Picture Transfer Protocol) or MTP (Media Transfer Protocol) device. PTP is the older standard, designed for digital cameras. MTP is Microsoft's extension that handles a wider range of file types. iPhones use a variant of PTP that only exposes the DCIM photo folders, which is why you can browse photos over USB but not arbitrary files.

Android phones typically use MTP, which exposes more of the filesystem. Connect an Android phone via USB, tap the "Charging this device via USB" notification, switch to "File Transfer" mode, and the PC mounts the phone's storage as a browsable drive. You can copy files in either direction.

USB transfer speeds depend on the protocol version. USB 2.0 (most Lightning cables) maxes out at 480 Mbps theoretical, with real-world throughput around 25-35 MB/s. USB 3.0 (some USB-C connections) jumps to 5 Gbps theoretical, delivering 200-400 MB/s in practice. The bottleneck is usually the phone's flash storage rather than the cable.

The advantage of USB: it works everywhere, with no network of any kind. No WiFi, no Bluetooth, no internet. The disadvantage: you need a cable, you need the right cable (Lightning vs USB-C, USB-A vs USB-C on the PC end), and on iPhones you're limited to photos unless you use iTunes or a third-party tool.

Local WiFi Without a Router

Most people associate WiFi with an internet connection. They're separate things. WiFi is a local radio protocol. Internet is a connection to external networks. You can have WiFi without internet, and that WiFi can transfer files just fine.

Two approaches work here. The first is WiFi Direct, a standard that lets two devices create an ad-hoc WiFi connection without a router. One device acts as a software access point, the other connects to it. Android supports WiFi Direct natively. Windows supports it through various apps. iOS support is limited (Apple prefers you use AirDrop, which has its own WiFi Direct-like mechanism under the hood).

The second approach is a phone hotspot. Turn on your phone's mobile hotspot (without cellular data, just the local WiFi network it creates). Connect your PC to that hotspot. Both devices are now on the same local network. No internet flows through it, but local traffic works perfectly. Any LAN-based file transfer tool will function over this connection.

OpenDrop works over a phone hotspot because it uses standard HTTP over the local network. The desktop server starts on port 8000, mDNS broadcasts the service type _opendrop._tcp.local., and the other device discovers it. The transfer stays entirely local. I've used this in hotel rooms where the WiFi was too slow or unreliable: turn on my iPhone's hotspot, connect my laptop, and transfer files at local WiFi speeds without touching the hotel network.

Hotspot-based transfers are faster than you'd expect. Even without cellular data flowing, a phone hotspot creates a WiFi network capable of moving data at the phone's WiFi radio speed. For a modern phone, that's WiFi 5 or WiFi 6 speeds between devices connected to it.

HTTP Over a LAN (No Internet Required)

This deserves its own section because it's the most misunderstood option. HTTP is a protocol, not an internet service. You can run an HTTP server on a device and have another device on the same network make HTTP requests to it. No internet connection involved. The data travels from device to device through whatever network they share, whether that's a home router, an office switch, or a phone hotspot.

The mechanism is straightforward. One device runs a web server bound to its local IP address and a port (OpenDrop uses port 8000). Another device sends HTTP requests to that IP and port. The server responds with data. For file transfer, the client sends a POST request with the file in the request body, and the server writes it to disk.

Device discovery is the challenge in an offline scenario. On a normal network, mDNS handles this: the server broadcasts its presence, clients listen for the broadcast. mDNS uses multicast UDP on port 5353, which works on most home and office networks but can be blocked on restrictive networks.

When mDNS doesn't work, you need another way to tell the client where the server is. OpenDrop solves this with QR code pairing. The server generates a QR code containing its local IP address and port. The client scans the code and connects directly. No discovery protocol needed, no internet needed, just a camera pointed at a screen.

HTTP-based LAN transfer is what most modern file sharing apps use under the hood. The protocol is well-understood, every platform has HTTP libraries, and it handles large files natively through streaming request bodies. Adding authentication (OpenDrop uses HMAC-SHA256 with a shared secret) prevents unauthorized devices from accessing the server.

Bluetooth: The Slow Option That's Always There

Bluetooth file transfer uses the OBEX (Object Exchange) protocol, originally designed for exchanging business cards between PDAs in the late 1990s. The protocol still works, and it's available on virtually every phone, laptop, and tablet manufactured in the last 15 years.

The speed hasn't kept up. Bluetooth 5.0 has a theoretical maximum data rate of 2 Mbps for classic Bluetooth (the mode used for file transfer). Real-world throughput is typically 200-300 KB/s. Bluetooth Low Energy (BLE) is faster for small data packets but isn't designed for bulk file transfer.

To put that in perspective: a 1GB file takes about 55 minutes at 300 KB/s. The same file over a WiFi LAN transfer takes seconds. Bluetooth file transfer is two orders of magnitude slower than WiFi for bulk data.

Bluetooth also has pairing friction. Both devices need to be in discoverable mode. You select the target device from a list. Sometimes you confirm a pairing code. On some Android versions, you need to explicitly enable Bluetooth file sharing in settings. iOS doesn't support standard Bluetooth file transfer at all (Apple routes everything through AirDrop instead).

Where Bluetooth makes sense: transferring a single contact card, a small document, or a photo when you have absolutely nothing else available. No WiFi, no cable, no USB drive. Just two devices with Bluetooth radios. The range is about 10 meters, the speed is glacial, but it works without any infrastructure whatsoever.

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

Sometimes the fastest network is a person walking between two computers carrying a USB drive. This is only half a joke.

A USB 3.0 flash drive reads and writes at 100-200 MB/s. A portable SSD over USB 3.2 can hit 1000+ MB/s. For a one-time transfer of a very large dataset (50GB, 100GB, an entire photo library), physical media can be faster than any wireless method simply because the read/write speeds are so high and there's no network overhead.

The workflow is crude but effective: copy files to the drive from device A, physically carry the drive to device B, copy files from the drive. For phones, you need an adapter (Lightning-to-USB, USB-C OTG) and an app that can access external storage. Android handles this natively through the Files app. iOS added external storage support in iOS 13 through the Files app, though it's pickier about file systems (prefers exFAT or FAT32).

SD cards serve the same role in a smaller form factor. Many laptops still have SD card slots. Phones rarely do anymore (most manufacturers dropped the microSD slot years ago), but USB-C card readers bridge the gap.

Physical media is the only method on this list that works with truly zero electronics on the receiving end during transfer. The drive holds the data independently. You can transfer files between two machines that are never powered on at the same time, which matters for some air-gapped or security-sensitive environments.

Choosing Based on What You're Actually Transferring

Each method has a sweet spot defined by file size, available hardware, and how often you do this.

A few small files (under 50MB): Bluetooth works if both devices support it and you don't mind waiting. USB is faster if you have a cable handy.

Medium transfers (50MB to 5GB): Local WiFi is the best balance of speed and convenience. A phone hotspot creates the network if no router is available. OpenDrop or similar tools handle the actual transfer over that local connection. On my test setup, I regularly move multi-gigabyte files between my iPhone 15 and my Windows desktop this way.

Large transfers (5GB+): USB cable or a fast external SSD. WiFi LAN transfer works too, but raw throughput matters at this scale and wired connections are faster. If you have a USB 3.0 cable and port on both sides, that's the fastest option.

Regular recurring transfers: Set up a local WiFi transfer tool permanently. OpenDrop runs on Windows, macOS, Linux, iOS, and Android. Install it on both devices, and any future transfer is a tap-and-send operation. No cables, no drives, no searching for the right adapter. Even without internet, as long as both devices are on any shared WiFi (including a phone hotspot), transfers work.

The internet is useful for many things, but moving files between your own devices in the same room isn't one of them. Every method here works offline, and most are faster than uploading to a cloud service and downloading on the other end.