Why Is My Upload Speed So Slow? UK Causes, Fixes and Real Data
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You run a speed test, the download figure looks healthy, and then the upload number lands at a fraction of it. For most UK households that isn't a fault. It's how the line was built. But a slow upload is the reason video calls freeze when someone else is backing up their phone, and why a 2 GB file takes most of a lunch break to send.
Below: why upload lags download on most UK connections, how much you need, what you can fix yourself, and what real UK households get, from our own speed test results.
Data as of October 2026
All figures from our data are medians from 6,254 tests run on BroadbandSpeedTest.uk.com from UK connections between 1 March and 15 September 2026. VPNs, data centres and unidentified providers are excluded. See our methodology for how results are filtered, and the September 2026 speed report for the latest monthly figures.
The Short Answer
Upload is usually slow for one of three reasons, in this order of likelihood:
- Your connection type caps it. Part-fibre (FTTC) lines top out at 20 Mbps upload. Virgin Media's cable network and Openreach's full fibre are faster but still lopsided. Only some full-fibre networks give you the same speed in both directions.
- Something in your home is already uploading. Phone photo backup, OneDrive or Dropbox sync, a security camera or a games console uploading clips can quietly use most of a small upload allowance.
- Wi-Fi is the bottleneck. Phones and laptops transmit with far less power than your router, so the upload direction suffers first when you're a few walls away.
The quickest way to tell which applies to you is to plug a laptop into the router with an Ethernet cable, pause cloud backups, and run a test. If upload is still around 20 Mbps or less, your package or line type is the limit. If it jumps, the problem is inside your home.
Upload Speeds in Our Data
Across all 6,254 tests, the median upload was 68 Mbps against a median download of 151 Mbps. That average hides a split country. Among fixed-line tests (5,911, excluding Starlink and mobile networks), 23% uploaded at under 20 Mbps, while 36% managed 100 Mbps or more. Which side you land on depends mostly on which network you're on:
| Network group | Tests | Median download | Median upload | Upload under 10 Mbps |
|---|---|---|---|---|
| Independent full fibre (altnets) | 1,035 | 453 Mbps | 234 Mbps | 2.0% |
| Zen, IDNet, ICUK, Aquiss, Andrews & Arnold | 336 | 533 Mbps | 106 Mbps | 6.5% |
| Virgin Media | 784 | 375 Mbps | 85 Mbps | 3.4% |
| Vodafone | 481 | 146 Mbps | 65 Mbps | 18.5% |
| BT, Sky and TalkTalk | 2,799 | 90 Mbps | 29 Mbps | 19.9% |
| Three and O2 (mobile / 5G) | 309 | 59 Mbps | 17 Mbps | 45.0% |
| Starlink | 34 | 103 Mbps | 6.4 Mbps | 58.8% |
Altnets here are YouFibre, toob, BRSK, Community Fibre, Fibrus, Trooli, Gigaclear, Hyperoptic, Vision Fibre Media, Full Fibre, AllPoints Fibre, Grain Connect and other smaller independent full-fibre networks. Results include Wi-Fi, so they sit below the speeds delivered to the router.
The headline gap partly reflects the fact that many BT, Sky and TalkTalk customers are still on part fibre. So we also compared like with like. Looking only at tests that downloaded at 500 Mbps or more, which are almost certainly full-fibre or top-tier cable lines, the download medians are close but the upload medians are not:
- Altnets: median upload 373 Mbps (473 tests)
- BT, Sky and TalkTalk: median upload 105 Mbps (426 tests)
- Virgin Media: median upload 100 Mbps (298 tests)
At the other end, BT, Sky and TalkTalk tests that downloaded between 30 and 80 Mbps, the range typical of part fibre, had a median upload of just 18 Mbps (918 tests). That matches the 20 Mbps ceiling of FTTC almost exactly. You can see upload figures for each provider on its page, for example BT, Virgin Media, Community Fibre and toob.
Why Upload Is Slower Than Download
Broadband was designed around consumption: web pages, streaming and downloads flow towards you, and only small requests flow back. Engineers split the available capacity accordingly, and each UK network type does it differently.
Part fibre (FTTC): hard-capped at 20 Mbps
On FTTC, the copper between the street cabinet and your home carries both directions using VDSL2, which allocates most of its frequency range to download. Openreach's fastest FTTC profile is 80 Mbps down and 20 Mbps up, and longer copper runs get less of both. No router upgrade or setting can lift you above that cap. Our FTTP vs FTTC guide covers the technology in more detail.
Virgin Media cable: faster, but still lopsided
Virgin Media's cable network uses DOCSIS, where the upstream channel is much narrower than the downstream. Our data shows this clearly: Virgin tests with gigabit-class downloads cluster at about 100 Mbps upload, and three-quarters of all Virgin tests uploaded at 100 Mbps or less. That is plenty for most homes, but it's a ceiling.
Openreach full fibre: much faster, not symmetric
A common misconception is that all full fibre is symmetric. Openreach's FTTP, which BT, Sky, TalkTalk, Vodafone, Zen and many others resell, is not. Its products upload at a fraction of the download speed, with the top gigabit-class tiers at roughly 110–120 Mbps upload. Our numbers back this up: BT, Sky and TalkTalk tests downloading over 500 Mbps had a median upload of 105 Mbps. That's five times faster than FTTC, but nowhere near the download figure.
Altnet full fibre: often symmetric
Many independent full-fibre networks sell symmetric packages, where a 500 Mbps plan uploads at 500 Mbps too. That's why altnet tests in our data upload at a median of 234 Mbps overall and 373 Mbps at the top end. If upload matters to you, the network matters more than the brand. Our altnets vs Openreach comparison breaks this down by provider.
4G, 5G and Starlink: upload is the weak spot
Wireless home broadband has to send your upload from a small antenna back to a mast or satellite, so it's the first thing to suffer. In our data, Three and O2 connections had a median upload of 17 Mbps, and Starlink just 6.4 Mbps from 34 tests. See our Starlink UK results for more.
How Much Upload Speed Do You Need?
Less than you might think for calls, and more than you might think for anything involving files. These are typical figures per activity, so add them together for everything that happens at once in your home:
| Activity | Typical upload used |
|---|---|
| One HD video call (Teams, Zoom, Google Meet) | About 1.5–4 Mbps |
| Two people on video calls at once | About 5–8 Mbps |
| Online gaming (game traffic only) | Under 1 Mbps |
| Cloud-connected security camera | About 1–4 Mbps each |
| Live streaming at 1080p (Twitch, YouTube) | About 6–10 Mbps |
| Live streaming in 4K | 20 Mbps or more |
| Cloud backup, photo sync, sending large files | As much as you can get |
For calls and gaming, the raw number matters less than headroom. A 20 Mbps upload copes with a household of video callers, until someone's phone starts backing up 500 holiday photos and fills the pipe. For files, upload speed translates directly into waiting time. Here's how long a 100 GB backup (a typical phone and laptop photo library) takes at different upload speeds, before overheads:
- 10 Mbps: about 22 hours
- 20 Mbps (FTTC maximum): about 11 hours
- 100 Mbps: about 2 hours 15 minutes
- 500 Mbps: about 27 minutes
For a home worker sending video edits, CAD files or large datasets, that difference is a working day. Our working from home guide goes through which packages suit which jobs, and what counts as a good broadband speed covers download needs.
How to Fix Slow Upload Speed
Work through these in order. The first three cost nothing.
1. Test with a cable to find your true ceiling
Plug a laptop into the router with Ethernet and test. If the wired upload matches your package, your line is fine and the problem is Wi-Fi or a busy device. Our Wi-Fi vs Ethernet guide explains how to run a fair comparison.
2. Check what upload your package promises
Look at your contract summary or order confirmation. Many people discover their full-fibre plan is an entry tier with about 30 Mbps upload, or that they're still on FTTC. If your wired result matches the contracted upload, there's nothing to fix at home.
3. Find what's already uploading
iCloud Photos, Google Photos, OneDrive, Dropbox, backup software, security cameras and consoles sharing gameplay clips all upload in the background. Pause them and test again. Most ISP router apps show live usage per device, which is the fastest way to spot the culprit.
4. Stop uploads wrecking calls and games
When the upload pipe is full, everything queues and ping shoots up. Our test shows this as "loaded latency" during the upload phase. If your router has Smart Queue Management (SQM) or a QoS setting, cap upload at about 85–90% of your measured wired speed. Calls and games stay responsive even while a backup runs. You can also schedule backups overnight.
5. Fix the Wi-Fi uplink
Phones and laptops transmit with much less power than your router, so upload drops off faster than download as you move away. Use 5 GHz where possible, move closer to the router, or add a mesh node near where you work. Our Wi-Fi speed guide has more fixes.
6. Check VPNs, powerline adapters and old kit
VPN encryption costs speed in both directions (see VPN speed loss). Powerline adapters and older switches or USB Ethernet adapters limited to 100 Mbps can also cap uploads on faster lines.
When Switching Is the Only Fix
If your wired upload already matches your package, the only way to go faster is a different package or network. In rough order of upload gain:
- FTTC to Openreach full fibre: from a 20 Mbps cap to about 30–120 Mbps, depending on tier. Same providers, so it's often a simple upgrade.
- Any asymmetric line to a symmetric altnet: from about 100 Mbps to several hundred. This is the only way most UK homes get upload equal to download.
- Higher tier on your current network: on Openreach full fibre and Virgin Media, faster tiers usually come with more upload too. Check the upload figure before you pay more for download you don't need.
Ofcom's Connected Nations 2025 report puts full-fibre availability at 78% of UK homes, so it's worth checking your postcode even if you looked a year ago. Our switching guide covers the process, and the monthly speed reports track how upload speeds are moving across the UK.
FAQ
Is 20 Mbps upload good?
It's enough for a household of video callers and gamers, as long as nothing else is uploading at the same time. It's slow for cloud backup, sending large files or live streaming in high quality. It's also the maximum FTTC can deliver, so if you have 20 Mbps on part fibre you're already at the ceiling.
Is Virgin Media upload symmetrical?
No. In our data, Virgin Media tests had a median upload of 85 Mbps against a median download of 375 Mbps (784 tests). Even on gigabit-class results, upload clustered at about 100 Mbps.
Does upload speed affect gaming?
The game itself uses well under 1 Mbps. What hurts is a full upload: when another device saturates it, your ping spikes and you get lag. That's why SQM or scheduling backups often fixes "random" lag better than a faster package. See what counts as good ping for gaming.
Will full fibre fix my slow upload?
It will improve it dramatically if you're on FTTC, but how much depends on the network. Openreach full fibre gives you several times the FTTC upload; a symmetric altnet gives you the same upload as download. Read full fibre vs part fibre to check what you have now.