Sending large files from your phone without failed transfers

Large transfers from a phone usually fail for one of four reasons: the screen locks and the operating system pauses the app or browser tab, the receiving device runs out of memory, the battery or data plan gives out, or the method has a size cap you did not know about. The fix is to pick a method that suits the file size, then keep the sending app in the foreground with the screen on, the phone plugged in, and Wi-Fi rather than mobile data. For multi-gigabyte videos, an installed app or a cloud upload that can run in the background is often more reliable than anything that runs in a browser tab.

What goes wrong, and the fix for each

1. The screen locks and the transfer freezes

iOS and Android both aggressively limit what apps can do when they are not on screen. A browser tab in the background, or a browser whose screen has locked, typically has its network activity paused or killed within a short time. For a live, peer-to-peer transfer that is fatal, because the other side is waiting on a connection that has gone quiet.

Fix: raise the auto-lock time for the duration of the transfer and keep the sending app in front.

• iPhone: Settings > Display & Brightness > Auto-Lock, choose a longer time or Never, and set it back afterwards.
• Android: Settings > Display > Screen timeout (the exact wording varies by manufacturer).
• Do not switch apps to "just check something". Answering a call is usually fine on modern phones; opening the camera or a game often is not.

2. Low Power Mode and battery savers quietly fight you

Battery saving modes tighten the screws further. Apple's documentation says iPhone Low Power Mode sets Auto-Lock to 30 seconds and turns off Background App Refresh, among other things. Android battery savers and manufacturer "optimisation" features restrict background activity in similar ways, and some brands are more aggressive than others.

Fix: plug the phone in and turn off Low Power Mode or battery saver until the transfer finishes. Sending gigabytes over Wi-Fi with the screen on uses real power; starting at 15% is asking for trouble.

3. The receiving phone runs out of memory

This one is less obvious and depends on the receiver, not the sender. When a file arrives through a web page, the browser must either write it to disk as it arrives or collect it in memory and save it at the end. Desktop Chrome and Edge can stream large incoming files straight to a folder. Safari, Firefox and most mobile browsers generally cannot do that for web apps, so the whole file is assembled in memory first. Phones give each browser tab a limited amount of memory, and a tab that asks for too much gets reloaded or crashes.

We will be direct about our own tool here. TransferFiles.net works in mobile browsers and imposes no size limit, but when the receiver is on a phone, the file is held in browser memory until it is saved. Modest file sizes are rarely a problem, but multi-gigabyte files sent to a phone may fail, and there is no resume. Sending from a phone to a desktop running Chrome or Edge avoids the problem because the desktop can stream to disk.

Fix: for multi-gigabyte files to a phone, use an installed app (LocalSend, Quick Share, AirDrop) or a cloud service, which download to storage rather than memory. Or split a big batch into several smaller transfers.

4. The method has a size cap

Email attachments top out at tens of megabytes (see email attachment size limits). Messaging apps compress video and cap file sizes. Free cloud tiers have storage quotas: a Google account, for instance, includes 15 GB shared across Gmail, Drive and Photos. Google's Quick Share QR code route for sending to Apple devices allows up to 10 GB every 24 hours. Check the cap before you start a 30-minute upload.

Choose a method by size

Device to device in the same room is almost always the best route for very large files, because the data goes across your Wi-Fi or a direct radio link instead of through your internet connection. If you are crossing between iPhone and Android, our iPhone to Android guide lists which phones can now use Quick Share with AirDrop.

Wi-Fi or mobile data?

A transfer uses roughly the file's size in data on each end. A worked example: you send a 6 GB 4K video to a friend.

• Peer to peer, both on Wi-Fi: no mobile data used.
• Peer to peer, you on mobile data: about 6 GB from your plan.
• Cloud link, you on mobile data: about 6 GB from your plan to upload, and your friend uses 6 GB more to download. If they are also on mobile, it counts against their plan too.
• Cloud backup with auto-sync on mobile data: may keep uploading every new video, which is how plans get drained without anyone noticing.

Mobile upload speeds also tend to be well below download speeds and vary with signal strength, so a large send over 4G or 5G can take much longer than the speed test on your phone suggests. Use Wi-Fi for anything over a gigabyte if you can. More on this in mobile data usage for large files.

Pre-flight checklist for a big transfer

1. Phone plugged in, or above 50% battery.
2. Low Power Mode or battery saver off.
3. Auto-lock or screen timeout raised (remember to restore it).
4. On Wi-Fi, ideally close to the router. Other heavy uploads (cloud photo backup, video calls) paused.
5. Enough free storage on the receiving device, plus some headroom.
6. The receiver knows to keep their screen on as well, if the method is live.
7. For huge batches, split into a few transfers so one failure does not cost you everything.

Picking the files: iPhone and Android specifics

iPhone

• Photos and videos picked from the Photos library may be stored in iCloud and need to download to the phone first if iCloud Photos uses "Optimize iPhone Storage". That can look like a stalled transfer. Open the video in Photos and let it fully load before sending.
• Received files from browser transfers land in the Files app, usually in Downloads. Move videos into Photos from there via Share > Save Video.
• iPhone videos are HEVC by default. If the recipient needs H.264, change Settings > Camera > Formats to Most Compatible before recording, at the cost of larger files.

Android

• The system file picker shows Photos, Downloads and storage locations; long-press to select several files.
• Chrome saves received files to Downloads. Very large files need matching free space on internal storage, not on an SD card unless you change the download location.
• Some manufacturers add their own background-app killers on top of Android's. If transfers keep dying, look for battery optimisation settings for your browser or transfer app and set it to unrestricted while sending.

When a cloud upload is the better answer

Live transfers need both people online at once. If your recipient is in another time zone, or you want to start the upload and put the phone in your pocket, a cloud service is the better fit. Google Drive, iCloud Drive, Dropbox and WeTransfer's apps can all keep uploading in the background more gracefully than a web page can, and the recipient downloads whenever they like. The trade-off is a storage quota, an account, and the file sitting on someone's server until it expires or you delete it. For an overview of options for big videos specifically, see how to send large video files free.

Sources

• Apple Support: Use Low Power Mode to save battery life on your iPhone
• Apple Support: Using HEIF or HEVC media on Apple devices
• Google Pixel Help: Use Quick Share on your Android device
• Google One Help: storage shared across Gmail, Drive and Photos
• LocalSend official site