The vast majority of UK ISPs now offer unlimited broadband deals. Unlimited packages offer peace of mind - no danger of going over the download limit when there isn't one - but the ISPs often suggest that 'unlimited' packages will be good for downloading files, which is far from true.

That being the case, what does make the best broadband for downloading? It's a holy trinity of best broadband features for downloads: fair traffic management, fair or non-existent fair use and fast speeds. We'll look at all three in this guide.

What is downloading?

But, first, let's just define our terms: what is downloading anyway and why does it matter?

All online activity is downloading of a sort, even viewing web pages means downloading information.

Some activities are much more data hungry than others, however.

We'd put online activities in the following general order, from the least GBs consumed per second to the most:

• Browsing web pages
• Emailing
• Streaming content (e.g. iPlayer, Spotify, YouTube)
• VoIP (e.g. Skype)
• Online gaming
• P2P downloading

Although what we'll talk about in this guide applies to all internet activity, then, it's in the bandwidth heavy activities like P2P and gaming and downloading individual files of any size, where it'll really show.

Even unlimited deals can restrict the most bandwidth heavy activities by using traffic management, fair use agreements or simply as a result of low speeds.

If you've ever had to wait hours for a file to download or had your TV show interrupted by buffering, that will matter to you.

Putting downloads in the fast lane

1. The best traffic management policies

A traffic management policy is exactly what is sounds: the amount of bandwidth a broadband provider allocates to online activities to keep everything running smoothly.

Broadband providers are forced to manage traffic like this to some extent so that high bandwidth activities don't completely drown ordinary online activity, like browsing, that takes up very little space.

It's hard to visualise exactly what this means for downloads in practice so we're grateful to whoever uploaded the following YouTube video which shows a Be broadband connection, without any traffic management, and a BT connection downloading side by side.

As you can see, or if you didn't watch it, the unmanaged connection (from Be broadband) is definitely in the fast lane.

So traffic management is a bad thing? Not quite. Although we love unmanaged connections, traffic management policies that favour downloads can have just as dramatic an effect on your online experience.

For example, Plusnet offer a £5 add-on to their broadband deals called Plusnet Pro, which prioritises downloads, gaming and VPN traffic.

We'd be willing to bet that the deal is better for downloads than Sky broadband unlimited and fibre, which also does without a traffic management policy but has a far higher contention ratio than Be, meaning that customers are fighting it out for space.

Along with Be broadband, Sky and Plusnet with the Pro add-on, Eclipse internet has a good reputation for traffic management: broadband customers can use a simple tool to prioritise their own connections.

For more on these providers, see our full reviews here:

• Be broadband - review here
• Plusnet - review here
• Sky - review here
• Eclipse - review here

2. How speeds affect downloads

As we saw in the last section, the way that broadband providers manage connections is vitally important to downloads.

But fast speeds certainly don't hurt, either.

Here's a quick guide to how broadband speeds should, in theory, affect downloads.

As you can see, for relatively small downloads there's little performance difference. Again, it's the larger downloads where you really need to watch out.

Fast speeds certainly help with downloads, then, which has thrown the cat among the pigeons a bit when it comes to the best broadband for downloads.

Specialist deals for gaming broadband (read more here) have all but disappeared, for example, as serious downloaders migrate to fibre. Although some of the providers offering the fastest deals, such as Virgin Media, manage traffic the boost in speed is such that downloads are still much quicker than they would be elsewhere.

See our comparison here to check availability for the fastest broadband in your area.

2. The best (and worst) fair use policies

Finally, those looking for broadband that's good for downloads must take into account their deal's download allowance: both in the form of the advertised cap on usage and the less obvious limits imposed by providers that have a fair use policy in place.

Like traffic management, fair use policies aim to stop the most data hungry users with unlimited deals from ruining everyone else's online experience by slowing those using the most bandwidth.

Even Be broadband have one to allow them to step in when one individual's downloading is heavy enough to affect multiple connections.

Having said that, though, some policies are fairer than others. See our guide on this for a full breakdown by provider.

In general, only the heaviest of downloaders need to worry about fair use policies slowing downloads.

Those downloading a lot at peak times are especially vulnerable as are those served by a market 1 (least competitive) exchange. Not only do providers in these exchanges charge a premium for broadband they often impose stricter rules on downloads than the provider's 'main' packages, even when both are advertised as unlimited.

If you live in a more rural area with less choice of broadband, then, not only are you likely to have an issue with downloads when it comes to everyday speeds, a fair use policy could slow you down even more.

The best advice for everyone, but particularly those in rural areas (more here if that's you), is to check and double check the small print on that unlimited broadband.