How to Transfer Files from Mac to Windows — Step by Step
Transferring files between Mac and Windows has always been awkward — email has limits, cloud uploads are slow, USB drives mean physical movement. DropLink solves it with peer-to-peer file transfer that works on both platforms natively. Here's the full workflow.
Quick answer
Install DropLink from the App Store on Mac and from the Microsoft Store on Windows (both free, under 50 MB, no account). Open both apps while connected to the same Wi-Fi — devices discover each other automatically via mDNS. Drag files on the Mac, pick the Windows device, and transfer directly over QUIC with TLS 1.3. Typical speed is 50+ MB/s on Wi-Fi 5/6. For cross-network transfers, DropLink falls back to iroh P2P with DERP relay, still end-to-end encrypted with BLAKE3 verified streaming.
Step-by-step
- 1
Install DropLink on your Mac
Download DropLink from the App Store on your Mac. It's a free native app that takes less than 50 MB. Once installed, open it — no account or sign-up required.
- 2
Install DropLink on your Windows PC
On your Windows machine, get DropLink from the Microsoft Store. Both devices should be on the same Wi-Fi network for instant LAN transfer, or on the internet for remote P2P transfer.
- 3
Open DropLink on both devices
When you open DropLink on each device, they will discover each other automatically via mDNS on the local network. You'll see the other device appear in the DropLink Vicini list.
- 4
Drag and drop your files
On your Mac, drag the files or folders you want to send into the DropLink drop zone. You can send multiple files at once — folders will be compressed to ZIP automatically.
- 5
Select the Windows device
Click the Windows PC in the peer list. DropLink will send a transfer request to the Windows side — the user there can accept or reject it, AirDrop-style.
- 6
Done!
Once accepted, files transfer directly between your Mac and Windows PC, end-to-end encrypted, at full network speed. No files pass through any server.
Common issues and fixes
- The other device does not appear in the Nearby list
Check that both devices are on the same Wi-Fi network (not guest Wi-Fi vs main Wi-Fi). On hotel, cafe and some office networks, AP isolation blocks device-to-device traffic: DropLink will detect this and suggest the internet P2P path instead. On Windows, check the firewall — when DropLink runs for the first time, allow it on Private and Public networks. On macOS, System Settings → Privacy & Security → Local Network must be granted to DropLink.
- Transfer is slower than expected
Run an iperf or speed test between the two devices to confirm the network is actually fast. If you are on Wi-Fi, check you are connected to the 5 GHz or 6 GHz band, not 2.4 GHz. Also check that no VPN on either machine is routing the LAN traffic through the WAN (this is a common slowdown). DropLink tunes QUIC for LAN, but it cannot beat the network's actual bandwidth.
- Transfer fails partway through
Check the idle timeout on your Wi-Fi router — DropLink uses QUIC keepalives every 5 seconds and closes connections after 30 seconds of idle. If you lose Wi-Fi temporarily (weak signal), the transfer will resume on reconnect using QUIC's connection migration (where supported) or restart the remaining bytes via range request on HTTP fallback.
- Internet transfer works but it is slow
The transfer may be going through the DERP relay instead of direct P2P — the UI shows whether you are on 'P2P diretto' or 'Relay'. Relay transfers are limited by the relay server's bandwidth. Direct P2P is usually faster but requires at least one side to allow inbound UDP (not all NATs permit this). Your home router is usually fine; corporate firewalls are often the problem.
How it works behind the scenes
Discovery: mDNS/Bonjour with TOFU
When you open DropLink on both Mac and Windows, each device publishes an mDNS service on _droplink._udp.local. with TXT records containing the device name, OS, QUIC port, and the SHA-256 fingerprint of its QUIC certificate. The other device picks up the announcement within seconds and verifies the fingerprint on first connection (Trust On First Use). No central server, no pairing codes.
Transport: QUIC with TLS 1.3 and BBR
Once discovered, transfers happen over QUIC (quinn 0.11) on UDP. TLS 1.3 is mandatory (TLS 1.2 is explicitly rejected). Cipher suites are ordered per architecture: AES-128-GCM first on Windows x86_64 (AES-NI), ChaCha20-Poly1305 first on Apple Silicon Macs. BBR congestion control with 1 MB initial window ramps up in ~10 RTT (~20 ms on LAN). The UDP socket uses 8 MB buffers and the stream receive window is 64 MB.
Remote mode via iroh + DERP
If the Mac and the Windows PC are on different networks, DropLink falls back to iroh 0.96 for NAT traversal. iroh wraps QUIC in the Noise protocol (IK handshake) with ed25519 identity and curve25519 key exchange. When NAT hole-punching fails, a DERP (Designated Encrypted Relay for Packets) relay forwards encrypted packets. The iroh public DNS discovery is disabled — only the DropLink-operated relay is used, so the device IP is never published to third-party DNS.
What speed to expect
On modern hardware (Wi-Fi 5/6 router, recent Mac and Windows PC) typical transfer speeds are 50+ MB/s, often limited by the slower device's disk. Gigabit Ethernet gives consistent 100+ MB/s. On Wi-Fi 4 / older routers expect 20–40 MB/s. Internet P2P transfers are limited by the slower upload of the two connections: the sender's upload is usually the bottleneck.
- Wi-Fi 5/6 LAN
- 50+ MB/s typical
- Gigabit Ethernet
- 100+ MB/s
- Wi-Fi 4 LAN
- 20–40 MB/s
- Internet P2P
- Limited by sender's upload
Is the Mac-to-Windows transfer secure?
Yes. On the local network, QUIC wraps the data in TLS 1.3 with a self-signed ECDSA P-256 certificate verified via TOFU (the fingerprint travels in the mDNS TXT record, so a man-in-the-middle would need to intercept multicast on your LAN — which is far harder than intercepting internet traffic). On the internet path, iroh uses Noise IK with ed25519 device identity and curve25519 key exchange, and BLAKE3 verified streaming ensures the bytes arriving on the Windows side exactly match what the Mac sent — no silent corruption, no tampering by a malicious relay. You can optionally enable password protection on the share for an additional access-control layer.
Technical FAQ
Do I need the same Wi-Fi password on Mac and Windows?
You need both devices on the same Wi-Fi network (SSID), yes. If your router has a 'guest' Wi-Fi that isolates clients, put both devices on the main Wi-Fi. Corporate networks with client isolation will require the internet P2P fallback.
What happens if I close DropLink mid-transfer?
The active transfer stops (QUIC stream is reset with the code CANCEL_BY_LOCAL = 1) and the receiver sees 'Cancelled by sender'. Partially-transferred files are cleaned up on the receiver side after 30 seconds.
Do I need to install DropLink on the Mac if I only receive?
For Mac-to-Windows (you sending from Mac), you need DropLink on the Mac. For Windows-to-Mac, you need DropLink on the Windows side. If the sender has DropLink and the receiver does not, the receiver can still get the file through the Web UI (the sender generates a link, the receiver opens it in any browser).
Can I transfer a folder with subfolders?
Yes. DropLink will automatically zip the folder before sending, with adaptive compression: Deflate level 6 for text and documents, Deflate fast for files larger than 10 MB, Stored (no compression) for already-compressed formats (mp4, jpg, zip). The 1 MB IO buffer minimizes syscalls on large trees.