Wi-Fi Web Server Setup in Sync

One device becomes the server, any browser becomes the client

Sync's Wi-Fi web server turns one device into a local file server that any other device on the same Wi-Fi network can browse from a plain web browser. There's nothing to install on the receiving side and no cloud account involved: it's a local-network feature, available on iPhone, iPad, Android and Mac. It isn't available on Windows.

What you need

Two devices on the same Wi-Fi network: the one sharing the files (running Sync) and the one receiving them (just needs a browser).
The Sync app, on the device doing the sharing. iPhone, iPad, Android or Mac, not Windows.
That's it. The receiving device doesn't need Sync installed; a browser is enough.

Turning on the web server

Open Sync on the device that has the files.
Start the Web Server.
Choose the file or folder you want to share.
Sync shows a local web address (an IP address and port on your own network).

That address only resolves for devices on the same Wi-Fi network. It isn't reachable from the internet.

Connecting from another device

On the second device, open any web browser.
Type in the address Sync showed you.
You'll see a listing of whatever was shared. Click a file to download it, or browse into a folder if more than one item was shared.

Larger files and video support partial content, so a stalled download can resume and video can start playing before the whole file has transferred.

Free vs. paid

The web server works on Sync's free tier, with one limit: free shares one file, up to 200 MB, at a time. Sharing more than one file at once, sharing a whole folder, or removing the 200 MB cap is part of Sync's paid upgrade: the same subscription or one-time lifetime purchase that unlocks every cloud drive, USB and external drive support, and an ad-free app.

A few things worth knowing

It's local-network only. Files are served directly from your device to whoever's on the same Wi-Fi; nothing is uploaded anywhere.
It's manual, not a background service. You turn it on when you want to share something, and it runs only while you're using it.
No Windows support. If you need to move files to or from a Windows PC, use USB and external drives or a shared cloud drive instead.

Share Files Over Wi-Fi Without Cables or the Cloud: the full walkthrough, including why this beats AirDrop for mixed-device households.
USB Drive Setup in Sync, by Platform: the offline alternative when Wi-Fi sharing isn't an option, including on Windows.

FAQ

Open Sync on the device with the files, start the Web Server, and choose what to share. Sync gives you a local web address: open that address in a browser on any other device connected to the same Wi-Fi network to see and download the shared files.

Do I need an internet connection?

No. It works entirely over your local Wi-Fi network: both devices just need to be connected to the same network. No internet connection or cloud account is involved.

Which devices support the Wi-Fi web server?

iPhone, iPad, Android and Mac. It's not currently available on Windows.

Is it free?

Yes, with a limit: the free tier shares one file up to 200 MB at a time. Sharing multiple files, whole folders, or larger files is part of Sync's paid upgrade (subscription or lifetime purchase).

No. Files are served directly from your device to the other device over your local Wi-Fi. Nothing is uploaded to the cloud or accessible outside your network.

Why can't I find the web server on my Windows PC?

It isn't built for Windows. On Windows, use a USB or external drive, or a shared cloud drive, to move files instead.