Broadband for streaming: what a 4K stream actually uses, what really stops your picture, and where the ceiling honestly is

The short version, and what it does not claim

Direct answer: For streaming, the ceiling is low and the streaming service sets it, so past about 25 Mbit/s a faster line stops buying you a better picture and starts buying you more pictures at once.

If you want the one line and nothing else: check your subscription tier, the device you are watching on and the app’s own quality setting before you buy anything to fix your picture. Everything below is the working, and the working here is unusually clean, because the best single piece of evidence belongs to Netflix.

Start with what a stream is. A film is not a download that goes faster on a faster line: it is a fixed rate of data arriving continuously, and the rate is chosen by the company sending it. Once your line carries that rate comfortably, sending it down a bigger pipe changes nothing about the picture, because the picture was already complete. The rest of this page is that sentence, evidenced.

What it does not claim is that speed is irrelevant, and the honest half is set out in full further down. The floor is higher than people expect and it stacks: NOW's figure is per streaming device, DAZN asks more for 1080p sport than Netflix asks for 4K drama, and three 4K streams at once is three times one. A household watching four screens at once, or sitting near the bottom of the range, has a real reason to buy more, and so does anyone who downloads or uploads around the watching.

This is the fifth guide in this series. The others answer the questions next to this one: which technology to buy, whose network you are on, what a video call really needs and what actually decides your ping.

What a 4K stream actually uses

Direct answer: Netflix recommends 15 Mbps or higher for 4K and publishes that 4K uses up to 7 GB an hour, and those two figures are the same number: seven gigabytes in an hour is about 15.5 Mbit/s.

Netflix publishes two figures on two different pages and, as far as we can tell, has never put them side by side. Its speed page recommends 15 Mbps or higher for ultra high definition. Its data page says the High setting uses up to 7 GB an hour, per device, for the same thing. Seven gigabytes is fifty-six thousand megabits, and an hour is three thousand six hundred seconds, so that is about 15.5 Mbit/s.

Those two numbers agreeing is the whole argument. It means Netflix’s 4K is not a thing that gets better with more room: it is a stream of a particular size, and a line that carries it carries it. The same stream on a 900 Mbit/s line is the same stream. What changes is how many of them fit alongside it, and what else the house can do while they run.

It is worth being precise about why a stream behaves this way, because the instinct is to assume the vendors are being modest. A film is encoded once, at a set of fixed quality levels, and the player picks one and asks for it. The player is choosing from a menu the service wrote, and the top item on that menu is as good as it gets. Give the player a bigger connection and it does not invent a better item; it simply gets the one it already wanted, sooner and more reliably.

That is also why buffering is not a speed problem in the way people assume. A player keeps a few seconds of video in hand, and it buffers when that reserve runs dry, which happens when delivery falls below the rate for long enough rather than when the total is small. A line that averages 200 Mbit/s and stalls for four seconds at a time will buffer a 15 Mbit/s stream. A line that steadily delivers 30 will not. Steadiness is the variable, which is why the section on peak time further down matters more than the headline figure.

Two things in that table are worth a second look. The first is how low the whole column is: nothing on it reaches 30 Mbit/s, and the largest figure any major service publishes for 4K is Apple’s 25. The second is the last row. Channel 4 publishes no connection speed requirement at all. Its minimum requirements page gates on browser and operating system version and names no figure. One of the UK’s biggest free streamers does not think the number is worth stating at all, which is its own kind of answer.

Our guides to upload against download speed and how much speed your household really needs do the same arithmetic for everything else the house does, and streaming in 4K without buffering is the shorter version of this section.

What really stops your picture going to 4K

Direct answer: What stops a household getting 4K is almost always the subscription tier, the browser, the app or the HDMI cable, and almost never the broadband.

Start with the plan, because it is the most common answer and the one nobody selling broadband mentions. Ofcom put it plainly in its own report, where it had to design its testing around the problem: “UHD resolution is only available to people subscribing to Netflix's Premium plan and not all content is available in higher resolutions” A household on a Standard plan cannot see 4K Netflix on a two-gigabit line, because there is no 4K to see.

Then the browser, which is the one that catches people who have checked everything else. Netflix caps Microsoft Edge on a Mac at Up to HD (720p). The identical browser on Windows is listed at Up to Ultra HD (2160p). Netflix caps Firefox and Opera at 1080p on every operating system it lists, and caps Chrome on a Mac at 1080p as well. Apple does the same thing on its own service: “In the latest version of Google Chrome, Mozilla Firefox, or Microsoft Edge on a Mac, Windows PC, or Android, compatible content will play in up to 1080p (HD).” 4K HDR there is Safari on a Mac and nothing else.

Then the cable and the socket behind the television. Netflix: “For 4K or HDR, make sure that devices and cables are plugged into an HDMI port that supports HDCP 2.2 or later (usually the HDMI 1 port).” And: “For the Premium plan, you need to use Premium High Speed HDMI or Ultra High Speed HDMI cables.” A copy protection standard on an HDMI port decides whether 4K appears, and no broadband product in the country addresses it.

All four are checkable in about two minutes and none costs anything. The plan is on your account page. The browser cap is avoided by watching in the app on a television or streaming stick rather than on a laptop, which is what almost everybody with a 4K television already does. The cable is the one that needs a look behind the furniture, and the tell is a picture that is fine on one HDMI input and not on another. The app’s own quality setting is the one most often left wrong, usually because somebody set it to save data on a phone years ago and it followed the account.

There is a fair point on the other side and it belongs here rather than buried. A broadband provider cannot reasonably be expected to explain somebody else’s subscription tiers on its own sales page, and it would look odd if it tried. What it could do, and none of them does, is stop presenting a figure like 4K needs 50 to 100 Mbps as though the line were the only variable. The gap is not that they fail to sell Netflix plans. It is that they describe a multi-part problem as a single-part one, in the part they happen to sell.

Netflix’s own troubleshooting list puts these in the same order we have. Its first item is not the connection: “Check which plan you have and make sure it supports the quality you'd like.” The connection appears further down, after the plan and the devices. Every UK broadband page we read reverses that, and most omit the plan entirely.

If your picture is fine but your Wi-Fi is not, why is my broadband or Wi-Fi slow and where to put your router cover the other end of the chain, and Wi-Fi 6 against 6E and 7 covers whether new kit would help.

Why every page gives you a different number

Direct answer: Across the UK provider pages we read, the published figure for 4K streaming runs from 15 Mbps to 100 Mbps for the same job, and three companies publish two different figures for it themselves.

Virgin Media is the clearest case and it is not a gotcha: both pages are live, both are dated, and both are Virgin’s. Its streaming advice page of June 2025 says you “you'll want at least 15 to 25 Mbps and a fast, stable connection to watch without buffering”. Its broadband speed page of April 2026 puts the same job at 50 to 100 Mbps. Four times the number, same company, same question.

Sky publishes Minimum speed: 25Mbps for 4K on one page and 15 to 35Mbps on another, and on the same page as the 25 tells you that “Most homes need a good download speed of around 50-100Mbps”. TalkTalk publishes 5Mbps for HD streaming on its help centre and 25 Mbps for the same thing on its guides site, and 30Mbps against 40-50 Mbps for Ultra HD. None of that is dishonest. It is what happens when several teams write about the same thing over several years and no standard exists to anchor any of it.

Plusnet’s streaming page is the tidiest illustration of the gap, because both halves are on one screen. It publishes “4K or ultra-high definition or UHD needs a minimum speed of 25Mb” and sells against it: “Choose the best broadband for streaming and make buffering a thing of the past with our ultrafast Full Fibre deals up to 900Mb.” That is 36 times the figure it prints itself, on the page where it prints it.

Hyperoptic is the one provider we read that publishes Netflix’s data figures, and it is worth seeing what it does with them. “Netflix uses about 1GB of data for every hour of streaming. This jumps to 3GB per hour if you're streaming in HD, and a whopping 7GB for Ultra HD.” Correct, and taken straight from Netflix. Its recommendation on the same page is “If you've got multiple devices streaming simultaneously and you're after super smooth Ultra HD, you should be looking at our 150Mbps service or above.” The 7GB figure is on the page. The arithmetic that turns it into fifteen megabits is not.

For a reader trying to decide something, the spread itself is the useful information. When nine companies answer the same question with figures between 15 and 100, no one of those figures is knowledge: the range is telling you that the question does not have a single answer, and that the people answering it have no shared standard to answer it against. The figures that do come with evidence behind them are the streaming services’ own, because those companies are describing a stream they encode themselves, and Ofcom’s, because Ofcom measured rather than estimated.

So the reading order is: take the service’s figure for the quality you actually watch, multiply by the number of screens your house runs at once, add headroom for everything else, and treat any provider figure that is wildly above that as marketing rather than as measurement. That is not a cynical rule. It is just the order the evidence supports.

Our guide to the minimum guaranteed download speed covers the one speed claim that is regulated, the broadband speed guarantee covers what you can hold a provider to, and why broadband is slower than advertised covers the headline figure itself.

The honest floor, and why it stacks

Direct answer: The floor is higher than people expect and it stacks: NOW's figure is per streaming device, DAZN asks more for 1080p sport than Netflix asks for 4K drama, and three 4K streams at once is three times one.

Everything above this point argues that the ceiling is low. This section is the other half, and a page that left it out would be selling a different kind of nonsense from the one it is arguing against.

The floor stacks because streams add up. Vodafone does the arithmetic on its own page and gets it right: “If you have three people in your household streaming Netflix in Ultra HD, that's 45 Mbps bandwidth being used at once.” EE puts the same point more generally: “Your broadband speed is shared between all connected devices. So, if four devices are using the internet at the same time, they'll each get roughly a quarter of the available speed.” Virgin Media says it too: “Remember that these speeds are per device. If others in your home are streaming, gaming, or downloading at the same time, you'll need even more speed to keep everything running smoothly.” On this, the providers are being straightforward and useful.

Live sport is the honest exception on quality as well as quantity. DAZN publishes 16 Mbps for full high definition, which is more than Netflix asks for 4K, and it explains what that buys in a sentence no other service matches: “All DAZN programmes and live streams are available in 1080p Full High Definition, which means that as long as you have an internet speed of around 16mbps, you should experience the highest quality of definition.” NOW’s requirement is “A minimum internet speed per individual streaming device of 12Mbps for Boost, or 30Mbps for Ultra Boost”. The likely reason is live sport running at a higher frame rate, though neither company says so, so that is our reading rather than theirs.

There is a second number a heavy-watching household should know, and it is not a speed. Netflix publishes data use per hour, per device: up to 1 GB an hour for standard definition, up to 3 GB for high definition and up to 7 GB for ultra high definition. Two hours of 4K a night, on one screen, is about 420 GB a month before anybody else in the house does anything at all.

Set that against what Ofcom measures households actually using. Its average across all UK connections is 583 GB a month, and on full fibre connections it measured more. A serious 4K household is therefore at or above the national average from the television alone, which is worth knowing before signing anything with a usage policy attached to the word unlimited.

Put the two halves together and the useful number is not a speed at all, it is a count. Work out how many streams your house runs at once, multiply by the figure the service publishes, and add headroom for everything else. Four 4K Netflix streams is sixty megabits on Netflix’s own figure. Then check the constraint that usually bites first, which is not the line: Netflix allows two devices at a time on its Standard plans and four on Premium, and Premium is the only plan that carries 4K. 1 person can stream at a time on a standard membership, 2 on Boost and 3 on Ultra Boost.

Our guides to gigabit broadband for families and 2Gb and 8Gb broadband cover the top of the market honestly, and whether unlimited broadband is actually unlimited covers the other thing heavy watching runs into.

The evening peak, which finally matters

Direct answer: Ofcom’s peak-time window is 8pm to 10pm, which on every other broadband question is the wrong window to care about. For streaming it is exactly the right one.

On our home working guide we had to point out that the congestion figures everybody quotes describe the evening rather than the working day. Here that caveat disappears, because the evening is the point. Across all connections, 8-10pm peak-time download speeds averaged 95% of maximum speeds.

By technology the gap is real and small. Ofcom measured full fibre holding 97.6% to 99.3% of its maximum between 8pm and 10pm, against cable’s 94.2% to 97.9% and about 92% on old ADSL. Its explanation of the difference is worth quoting because it is about where the congestion sits rather than about the cable itself: “The variation in speeds at peak-time (8-10pm) is often higher in cable connections due to network congestion occurring nearer to the customer, making it harder for cable operators to add the additional network capacity required to reduce the effects of congestion.”

Keep the size of that gap in proportion, though. A cable line advertised at 500 Mbit/s holding 94.2% at nine in the evening still delivers well over four hundred megabits, which is thirty 4K streams on Netflix’s own figure. Peak-time slowdown is real, it is measured, and on a modern line it is nowhere near the reason a picture buffers.

One caveat on all of the peak-time evidence, and it is the same one that runs through this whole series. Ofcom closed the Home Broadband Performance programme after March 2023, so these are the most recent independent measurements rather than current ones, and nothing has replaced them. Nobody is measuring this any more, which is worth knowing before you trust any comparison of these four, including ours. Three years is long enough for network investment to have changed the picture in either direction, and nobody can now say which.

What survives that caveat is the shape rather than the decimal places. Full fibre degrades less at peak than cable, because of where the congestion sits rather than because of the cable itself, and both degrade far less than a household streaming at nine in the evening would guess from the experience of buffering. If your picture stalls at peak on a modern line, the peak is rarely the reason, and the section above on what to check first is the better use of the evening.

One more measurement worth carrying, because it describes the direction of the whole market. Ofcom, in Connected Nations 2025: “data usage is growing more slowly than growth in the download speeds that networks can deliver - 10% growth for data usage compared to a 28% year-on-year increase for download speeds”. Speeds are growing nearly three times faster than the data households actually use.

Our guide to why broadband is slow at night covers peak-time fixes in detail, and why broadband is slower than advertised covers what the headline figure is really measuring.

Fix buffering, in this order

Direct answer: Five of the six steps below cost nothing, and the first three take a couple of minutes between them.

The order is the argument of the page in practical form. Three of the first four steps are about things the streaming service controls and one is about your house, and only the last is about broadband. Run them the other way round, which is what the adverts invite, and you can spend two years of contract on a problem that was a setting.

Step five deserves a line of its own because of how often it is the answer. A television is usually the furthest device from the router, it is often behind a cabinet, and it is frequently the only device in the house still on the 2.4 GHz band. A cable to the television, or moving it to 5 GHz, resolves more streaming complaints than any package change we have seen.

For step five, when to run an ethernet cable, 5 GHz against 2.4 GHz and mesh against extenders cover the options, and fixing Wi-Fi dead zones covers the room the television is in.

When a faster line genuinely is the answer

Direct answer: A faster package is the right answer for a household watching several streams at once, for anybody on a line near the bottom of the range, and for the downloads and uploads that happen around the watching. It is not the answer to a picture that will not go to 4K.

Four cases, and the first is the one most households will recognise. Several screens at once. Streams add, the arithmetic is simple, and this is the case where a bigger package does exactly what it says. Four 4K streams is sixty megabits on Netflix’s own figure, and a house that runs four screens while somebody downloads a game needs real headroom rather than the bare minimum.

Second, a line near the bottom of the range. Ofcom measured 4K streaming working on nearly everything advertised at 30 Mbit/s or above, which means a household below that is genuinely constrained, and it is the case where the standard advice is simply correct. On an old FTTC line the upload genuinely can be the problem: Openreach publishes up to 15Mbps and Ofcom measured 6 to 9 Mbit/s on the slower variants, which is where a group call and a file upload start to collide.

Third, everything that happens around the watching. Game downloads have grown faster than almost anything else a household does, cloud backups run in the background, and a household streaming two hours of 4K a night is already moving several hundred gigabytes a month before any of that. Ofcom’s average across all connections is 583 GB a month, and on full fibre it measured more.

Fourth, upload, which streaming barely touches and everything else does. If anybody in the house publishes video, backs up photographs or runs a camera, that is an upload question and it deserves its own arithmetic.

A fifth case is worth naming because it is the one that changes fastest. Televisions now come with their own apps, and those apps update themselves to newer codecs and higher frame rates without asking anybody. A household that bought a line sized for 1080p five years ago has quietly been watching more demanding streams ever since, and the figures on this page will drift upward over time even if nothing in the house changes. That is an argument for headroom rather than for the minimum, and it is the fairest case the industry makes.

What unites those four is that none of them is the picture. The picture is settled at a level almost every modern line clears, and the honest sales pitch for a faster package to a streaming household is about capacity and headroom. That is a good pitch. It is just not the one on the page.

Our technology guide compares the four in full, broadband and TV deals covers bundling the subscription with the line, and best broadband for streaming is the shopping list version of this section.

Streaming broadband at your postcode