Why iPhone file transfers disconnect when the screen locks

An iPhone file transfer can stop after the screen locks because iOS limits how long the transfer app can keep executing in the background. The phone may still be connected to Wi-Fi while the app can no longer send data or answer the other device. When the iPhone has joined a phone-created hotspot, that network connection has a separate lifetime to consider.

This explains a familiar symptom: a transfer works with the app open, then stalls on the other phone or computer after the iPhone locks. It does not mean every lock event disconnects Wi-Fi, or that every interrupted transfer has the same cause.

This article covers local transfers handled by an app on the iPhone, including ShareGo phone-to-phone sharing and its computer-browser connection. AirDrop and cloud services use their own transfer mechanisms; their behavior is not a test of what a local sharing app can do.

Wi-Fi connectivity and app execution are separate

Imagine downloading a video from an iPhone through a computer browser. The browser sends requests to a server running inside the phone app. For the download to continue, the computer needs a working network path to the phone, and the phone app needs execution time to read and serve the file.

Keeping the first condition does not establish the second. The Wi-Fi icon can remain visible even when the server has stopped responding. A browser timeout tells you that a request failed; it does not identify whether the network disappeared, the app stopped running, or another part of the operation failed.

The same distinction applies when the iPhone receives a file. It still needs to process incoming data and save the result. Being the receiver does not remove the need for app execution.

What extra background time can do

iOS provides a way for an app to request additional time for unfinished work as it moves into the background. Apple's beginBackgroundTask API is one such mechanism. The request can be denied, and the app must release the execution allowance when it expires.

That allowance is finite. Apple also documents that system conditions can end background execution early. There is no fixed number of minutes that a local transfer app can promise for every locked iPhone.

This matters most for larger jobs. A short transfer may finish while execution is still available. A longer transfer, or one that spends time preparing a video before sending it, may still be working when the allowance ends. Seeing one small file arrive after locking the phone does not establish that a larger batch will finish under the same conditions.

A hotspot can disconnect for a different reason

When an app joins a Wi-Fi network using Apple's hotspot configuration API, it can set a property called joinOnce. With that property enabled, Apple documents circumstances that remove the configuration and disconnect the network, including device sleep and more than 15 seconds in the background. See Apple's joinOnce reference.

Those 15 seconds describe one hotspot configuration policy. They are not a universal timeout for iPhone file transfers.

ShareGo's implementation reviewed on October 2, 2026 sets joinOnce to false when joining the peer's network. This avoids tying that join to the foreground-only lifetime of a one-time configuration. It does not grant extra execution time to the transfer app or guarantee that the network will remain available.

For ShareGo's same-Wi-Fi computer connection, the phone and computer already use their existing network. There is no additional hotspot to join. A transfer can still stall if iOS suspends the phone app, even though neither device has left that Wi-Fi network.

How ShareGo handles a background session

ShareGo separates the connection's state from the screen displaying it. In the reviewed implementation, putting the app in the background does not itself close the session. Ongoing sends, receives, file preparation, imports and history writes are tracked so that the app can request finite background execution for unfinished work.

The work after the last byte matters too. A received video may still need to be imported, and its result recorded in History. Finishing one file therefore does not release protection needed by another transfer or a pending save.

An open but idle session also requests a limited grace period when the app goes into the background. It shares the same system allowance with active work. It cannot remain ready indefinitely for a computer to start a download later: an ordinary incoming request on the local network does not wake ShareGo once iOS has suspended it.

When the allowance expires, ShareGo releases it. Expiration is not treated as a successful transfer or a user pressing Stop. On returning to the foreground, the app checks the connection and uses its recovery paths where possible. These are implementation choices, not a measured guarantee of uninterrupted transfer on every iPhone or iOS version.

What happens when you return to the app

For a computer connection, the next step depends on what survived while the phone was locked:

State after returning	What it means for the computer
The server and network are still usable	ShareGo can retain the existing session; check the browser's actual transfer result.
The network changed or the server must restart	Use the current address and approve the browser again if asked.
You explicitly stopped the session	Start a new connection; returning to the app does not undo Stop.

Keeping or restoring a connection does not automatically replay a failed browser upload. Nor does it prove that a partially received file is complete. Check the destination before retrying, especially when several files were in progress.

For an important large transfer, leaving ShareGo visible and the iPhone unlocked removes the background-execution variable while the file is being prepared, transferred and saved. If a transfer has already stopped, follow the interruption checks rather than resending the entire batch immediately.

ShareGo transfers files between phones and provides browser access from a computer without a desktop client. The computer connection guide covers setup, and Download links to the phone apps. If the device that locked was Android, its foreground services and wake locks need a different explanation.