Video calls freeze when you upload files? Here's why

Written by (LinkedIn) • Reviewed by Adrian James (LinkedIn)

Last reviewed: 26 October 2026

Quick summary: Video calls freeze when you send big files? Your upload lane is full. Why it happens, free fixes to try today, and when full fibre helps.

Video calls freeze when you upload files
Illustration: Video calls freeze when you upload files? Here's why

Video calls freezing when you send big files? Here's why, and the fix

If your video calls freeze whenever you send big files, your upload is almost certainly full. A call only needs about 1 to 4Mbps of upload, but a file upload grabs every bit of upload you have, and the call's video has to queue behind it. Part-fibre broadband usually has 20Mbps of upload or less, so a 5GB file can block the lane for half an hour. Today, pause or cap big uploads during calls and use a cable. For good, compare full fibre deals with more upload on BroadbandSwitch.uk, and check the average upload speed before you buy.

What it means for youChecked 26 October 2026

If a call is coming up: pause big uploads, or set your sync app to a lower upload speed, until the call ends.

If you send big files every day: compare broadband on upload speed, not just download. Full fibre upload ranges from about 20Mbps to as fast as the download, depending on the package.

If you're in Brighton and Hove: full fibre may already be outside your door. Openreach says most of the city is covered, but you have to order it.

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Key facts, verified 26 October 2026

  • Zoom recommends 3.8Mbps upload for 1080p HD video calls, 2.6Mbps for 720p group calls and 1.2Mbps for 720p one-to-one calls (Zoom, checked 26 October 2026).
  • Microsoft recommends 2,500kbps upload for Teams video meetings, and 4,000kbps for best performance (Microsoft Learn, updated 9 July 2026).
  • The fastest part-fibre (FTTC) service was launched with a 20Mbps upload, and many lines get less (ISPreview, 14 July 2011).
  • Openreach full fibre packages run from a maximum 20Mbps upload on a 115Mbps package to 120Mbps on an 1,800Mbps package (IDNet, checked 26 October 2026).
  • Virgin Media's average upload is 52Mbps on M500 and 104Mbps on Gig1, against 1,130Mbps average download on Gig1 (Virgin Media O2, 23 May 2023).
  • Hyperoptic says its 150Mb to 1Gb packages have equally fast upload and download speeds (Hyperoptic, checked 26 October 2026).
  • Under Ofcom's 2022 speeds code, providers that sign up must give a normally available upload speed before you buy, but slow upload doesn't give a right to exit (Ofcom, 2022).
  • Broadband ads quote average download speed at peak time, 8pm to 10pm, not upload (ASA, 23 May 2018).
  • Full fibre is available to 82% of UK homes (Ofcom Connected Nations, 13 May 2026).
  • More than 90,000 homes and businesses in Brighton and Hove can now get Openreach full fibre, and CityFibre has been building its own £80m network there since February 2021 (Openreach, 2 February 2026; CityFibre, 18 February 2021).

Who this is for: anyone whose Zoom or Teams calls freeze, stutter or drop when they send big files, back up to the cloud or share work. We've told it through a freelance designer in Brighton who rang her provider because client calls froze every time she sent artwork. Her download speed looked fine, and she'd never heard of upload speed. She's an example built from the calls we take, not a real customer.

Why does my video call freeze when I send a big file?

Direct answer: Because the file fills your upload, and the call's video has to queue behind it. A call needs only a few megabits, but a file upload takes everything it can get.

Broadband has two speeds. Download is how fast things come in, and upload is how fast things go out: your face and voice on a call, and the artwork you send to a client. On most UK broadband, upload is much slower than download, so think of it as a narrow lane out of your home.

A video call sends a steady trickle of small packets. A file upload is different: it speeds up until it fills the lane completely. Once the lane is full, everything else waits in a queue inside your router, and the call's packets join the back of it. By the time they arrive, they're too late to use, so the picture freezes or the sound turns robotic. Engineers call the long queue "bufferbloat", and the internet's standards body, the IETF, says managing queues can significantly reduce the delay (RFC 7567, 2015). Two published methods, FQ-CoDel and PIE, were designed to do exactly that, and they're what sits behind "smart queue" settings on some routers (RFC 8290; RFC 8033).

Our guide to why broadband drops on video calls covers the other things that can wreck a call, such as weak Wi-Fi. This guide is about the one that catches out people who send big files.

How much upload does a video call really need?

Direct answer: Not much: about 1 to 4Mbps for HD video, depending on the app. The call itself is rarely the problem; what else is uploading at the same time is.

Zoom recommends 3.8Mbps of upload for 1080p HD video and 2.6Mbps for a 720p group call (Zoom). Microsoft recommends 2.5Mbps for a Teams video meeting, and 4Mbps for best performance (Microsoft Learn, 2026). Even the best part-fibre line has several times that. So when a call freezes on a line that should cope, look at what else is sending: a file, a cloud backup, a photo library syncing to the cloud.

That's why our home working guide says upload is rarely the problem for calls on their own. Add a big upload, though, and it becomes the whole problem.

Why does my speed test look fine?

Direct answer: Because most people only read the download figure, and a normal test checks each direction on a quiet line. It doesn't show what happens to your ping when the upload is full.

The number that tells the real story is ping under load: how much your delay rises while the line is busy. A small rise is fine. A big jump means calls will suffer whenever files move. Our free UK Speed Test measures upload and ping under load, and gives your line a busy-line grade from A to F. Test on a cable, because Wi-Fi can muddy the result; our guide on testing your line or your Wi-Fi shows how.

How long does a big file take to send?

Direct answer: At 20Mbps, a 5GB file takes about 33 minutes. At 100Mbps, it takes under 7 minutes, and at 900Mbps, under a minute.

Broadband speeds are in megabits, but file sizes are in megabytes, and there are 8 bits in a byte. So a 5GB file is 40,000 megabits. Divide that by your upload speed in megabits per second and you have the time in seconds, before overheads. At 20Mbps, the lane is full for more than half an hour, and any call in that window is competing with the file.

Faster upload shrinks that danger window from half an hour to a couple of minutes. Our guide to broadband for creators and large uploads goes further for people who send big files for a living.

What can I do today, for free?

Direct answer: Send big files outside calls, cap your sync app's upload, use a cable for calls, and drop your video to 720p while files are moving.

A rough rule for capping: set your sync app to about half your upload speed while you're on calls. On a 20Mbps line, that's about 10Mbps, or around 1,250KB per second in apps that use kilobytes. If you can't run a cable, RouterMap shows where to put your router for a stronger Wi-Fi signal where you work.

Will full fibre fix it?

Direct answer: Usually it helps a lot, because more upload clears a big file in minutes rather than half an hour. It doesn't remove the queue on its own, so keep the free fixes too.

Upload varies a lot between packages, even on full fibre. Openreach full fibre packages run from a maximum of 20Mbps upload on a 115Mbps package to 120Mbps on an 1,800Mbps package (IDNet). Virgin Media's average upload is 52Mbps on M500 and 104Mbps on Gig1, about a tenth of its download (Virgin Media O2, 2023). Some full fibre networks are symmetric: Hyperoptic says its 150Mb to 1Gb packages have equally fast upload and download (Hyperoptic).

Full fibre is now available to 82% of UK homes (Ofcom, 2026), so there's a good chance it's already in your street. Our guide to what symmetrical upload is good for helps you decide whether same-speed-both-ways is worth it for you.

What upload speed should a home worker look for?

Direct answer: For calls and light sharing, 10Mbps or more. If you send big files every day, look for 50Mbps or more, and more again for big daily backups.

Every home is different, so try RightSpeed: it asks a few questions about who's online and what they do, including video calls, file uploads and cloud backups, and recommends both a download and an upload speed. It takes about 45 seconds.

Know what upload you actually need

RightSpeed works out the download and upload your home needs in about 45 seconds, including calls, big files and backups.

  • ✓Free, with no sign-up
  • ✓Home and business modes
  • ✓Then compare deals that match

Does my provider have to tell me the upload speed?

Direct answer: If it has signed up to Ofcom's speeds code, it must give you an upload estimate before you buy. But slow upload alone won't let you leave your contract without paying.

Ofcom's 2022 speeds code says providers must give a normally available upload speed when you buy online, and on other sales channels if you ask (Ofcom, 2022). The code's minimum upload speed is an estimate, not a guarantee, and its right to exit without penalty is tied to download speed only (Ofcom, 2022). Adverts quote average download speed at peak time, not upload (ASA, 2018). So the upload figure is worth finding yourself, before you sign.

Our guides to upload versus download speed and when poor speeds let you leave early go into more detail.

Can I get full fibre in Brighton and Hove?

Direct answer: Very likely. Openreach says more than 90,000 homes and businesses there can now get full fibre, and CityFibre has been building its own network across the city since 2021.

Openreach says its £27m investment has brought gigabit-capable broadband to around 63% of properties in the area, and that most of the city is covered, but many people haven't switched (Openreach, 2026). Back in November 2024, just 26% of people had taken it up where it was available (Openreach, 2024). CityFibre began its £80m city-wide build in February 2021 (CityFibre), and its network is sold by several providers. So our designer may well have full fibre outside her door already.

How do I switch without losing a working day?

Direct answer: Order with your new provider and let it handle the switch. Under One Touch Switch, you don't need to call your old provider, and any loss of service should be no more than one working day.

Ask for an installation date that avoids your busiest client days, and keep your current service running until the new line is live. Under One Touch Switch, your new provider arranges everything (Ofcom, 2024), and Ofcom's rules say the gap in service should be no more than one working day. If you order online or by phone, you also have 14 days to change your mind. If you're thinking about business broadband, our guide to home versus business broadband compares the two.

What should I do now?

Today: protect your calls

Pause or cap big uploads during calls, use a cable, and drop to 720p while files move.

This week: know your numbers

Test your upload and busy-line grade on our UK Speed Test, then use RightSpeed to see what upload you need.

When you're ready: compare

Compare deals for your address, and check each one's average upload speed before you buy.

Ready for calls that don't freeze?

Compare full fibre deals for your exact address, and pick one with the upload your work needs.

  • ✓Every deal for your address, side by side
  • ✓Full contract cost, including set price rises
  • ✓Your new provider handles the switch

In summary

  • Calls freeze during big uploads because the file fills your upload and the call's video queues behind it.
  • A video call only needs about 1 to 4Mbps of upload, so the call itself is rarely the problem.
  • Part fibre has up to 20Mbps of upload; full fibre ranges from about 20Mbps to as fast as the download.
  • Free fixes work today: send files outside calls, cap your sync app, use a cable and drop to 720p.
  • Ofcom's speeds code means you should get an upload estimate before you buy, but slow upload won't let you leave free.
  • Compare full fibre deals on BroadbandSwitch.uk, and check the average upload speed before you choose.

Alex's closing thought

I love calls like this one, because the fix is often free. Most people have never been told that broadband has two speeds, and the one on the advert isn't the one that sends your work. Once you know your upload is a single lane, the frozen calls make sense, and you can do something about them the same afternoon. If you send big files for a living, though, it's worth comparing on upload speed next time, because full fibre can turn a half-hour wait into a couple of minutes. And if you'd like a hand working out what you need, ring us. That's what we're here for.

Keep going: the guides behind this article

Know someone whose calls keep freezing?

Send them this. The fix might take them five minutes.

Cite this page

You're welcome to quote or link to this guide. Please credit BroadbandSwitch.uk and link back to this page.

Martin-Smith, A. J. (2026, October 26). Video calls freezing when you send big files? Here's why, and the fix. BroadbandSwitch.uk. https://broadbandswitch.uk/insights/video-calls-freezing-when-uploading-files/

In a sentence: BroadbandSwitch.uk's October 2026 guide explains that video calls freeze during big uploads because the file fills the home's upload and the call's packets queue behind it, that Zoom and Microsoft recommend only 2.5 to 4Mbps of upload for HD video, that part-fibre broadband offers up to 20Mbps of upload while full fibre ranges from about 20Mbps to symmetric, and that Ofcom's 2022 speeds code requires an upload estimate before purchase but gives no exit right for slow upload.

Frequently asked questions

Why does my video call freeze when I upload a file?

Because the file fills your upload, and the call's video has to queue behind it. A file upload speeds up until it uses all the upload you have, so the call's small, time-sensitive packets wait in a queue and arrive too late. Pause or cap the upload during calls, or get a connection with more upload.

How much upload speed do I need for Zoom or Teams?

Not much. Zoom recommends 3.8Mbps upload for 1080p HD video and 2.6Mbps for a 720p group call. Microsoft recommends 2.5Mbps upload for a Teams video meeting, and 4Mbps for best performance. The trouble starts when something else is uploading at the same time.

What is a good upload speed for working from home?

For video calls and light file sharing, 10Mbps or more is comfortable. If you send big files every day, look for 50Mbps or more, and 75 to 100Mbps or more for large daily cloud backups. RightSpeed can work out a figure for your home.

Why is my upload speed so much slower than my download?

Most UK broadband is built that way, because most people download far more than they upload. Part fibre has up to 20Mbps of upload, and many full fibre packages have a fraction of their download speed as upload. Some full fibre packages are symmetric, with the same speed both ways.

What is bufferbloat?

Bufferbloat is the delay that builds up when your router queues too much data. When a big upload fills the line, the queue grows and everything else, including your call, waits behind it. Routers that manage their queues, sometimes called smart queue management, keep that delay low.

Will full fibre stop my video calls freezing?

Usually it helps a lot, because more upload clears a big file in minutes rather than half an hour. It doesn't remove the queue on its own, though, so keep sending files outside calls or capping uploads. Check the average upload speed on each package before you buy.

How long does it take to upload a 5GB file?

Before overheads, about 33 minutes at 20Mbps, 13 minutes at 50Mbps and under 7 minutes at 100Mbps. At 900Mbps it takes under a minute. Add around 10% for real-world overheads and Wi-Fi.

How do I stop Dropbox or OneDrive slowing down my calls?

In Dropbox, go to Preferences, then Network, and turn on Custom bandwidth to set an upload limit. In OneDrive, open Settings, then Sync and back up, then Advanced settings, and set an upload rate or choose Adjust automatically. Google Drive for desktop lets you pause syncing.

Is a cable better than Wi-Fi for video calls?

Usually, yes. Microsoft says Wi-Fi networks aren't necessarily designed for real-time media, and a cable removes Wi-Fi interference from the picture. If you can't run a cable, RouterMap can help you find a better spot for your router.

Does my broadband provider have to tell me my upload speed?

If it has signed up to Ofcom's 2022 speeds code, it must give you a normally available upload speed before you buy. Adverts only have to quote average download speed at peak time, so check the upload figure yourself.

Can I leave my contract if my upload speed is slow?

Not under Ofcom's speeds code. Its right to exit without penalty only applies if your download speed falls below the minimum guaranteed, and the code's minimum upload is an estimate, not a guarantee. If you're out of contract, you can switch as normal.

How do I test my upload speed?

Run a speed test on a cable, not Wi-Fi, and look at the upload figure and the ping under load. Our free UK Speed Test measures download, upload, ping and jitter, and gives a busy-line grade from A to F.

References

Written by Dr Alex J. Martin-Smith, Founder (LinkedIn). Reviewed by Adrian James, Broadband Editor at BroadbandSwitch.uk (LinkedIn). Published 26 October 2026. The freelance designer in Brighton is an illustrative example built from the calls we take, not a real customer. BroadbandSwitch.uk is an independent comparison site and is not a broadband provider. RightSpeed, UK Speed Test and RouterMap are free BroadbandSwitch.uk tools. Speeds vary by address, line and package, and the rules quoted are those in force on the date shown. This is general information, not legal advice. Corrections are logged publicly.

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