Google Chrome using too much bandwidth?

After a recent Google Chrome update, I have found quite a big spike in my bandwidth usage. My allowance is 40GB per month at peak times and I have never gone over my allowance for the 12 months I have been with IDnet. By the 15th of this month I had already used 30+GB. A lot of people, including myself, have capped ADSL meaning that if we go over our monthly bandwidth allowance we get charged. In my case £1.03 per GB.

After trawling around the network looking for suspicous traffic nothing was apparent.

I downloaded Netlimiter ( download at: ) to see if there was anthing on my main PC consuming all this bandwidth. After a couple of minutes it was obvious that the culprit was Google Chrome browser. I generally leave Chrome running 24/7 with my homepage tabs on (all static pages) when I am not using it. I have never really messed about with the settings as it works perfectly on default settings. However, if you have “Prefetching” switched on then your browser will download fresh versions of all the most visited websites and your favourites etc in the cache so they load up instantly when you visit them.

This was confirmed when I watched the traffic via Netlimiter.

The first hour after installation, Chrome consumed 245MB (down) in 1 hour. The 2nd hour was roughly the same. After a couple of Google searches I found out how to disable prefetching.

1) Type: chrome://flags/ into the address bar and disable the option:
Prerender from omnibox Mac, Windows, Linux, Chrome OS. Enables prerendering of suggestions from the Omnibox and predicts appropriate network actions (prerendering, Instant, DNS preconnect) by calculating a confidence value for each Omnibox result.

2) Go to Chrome settings and click on “Under the Bonnet” and disable “Predict network actions to improve page load performance”.

This is from Google:
Predictions for network actions.
When you visit a web page, Google Chrome can look up the IP addresses of all links on the web page. Browsers use the IP address to load a web page, so by looking up this information in advance, any links that you click on the web page will load faster. Websites can also use prerendering technology to preload the links that you might click next.

Whilst the above suggests that it’s just caching DNS lookups it also seems to be downloading whole webpages and their contents. So basically when you open your browser it will look through your history and then look at which websites you visit most and then fetch them all to the browser cache for faster loading. Not only does it do this but it seems to follow links and do the same thing to those pages. After a while of being idle it starts all over again :/ This is what I have observed when starting the browser and watching traffic flow via Netlimiter 3. The most visited website IP addresses popped up and spawned lots of connections which peaked up to 200Kb /s and lasted for up to a minute each time. DNS prefetching would use bytes rather than MB’s.

Upon further inspection of previous logs from another program, I found this from Networx ( download Networx at: ):

Click pic to enlarge

As you can see, for 10 hours Chrome was using tons of bandwidth without me even knowing. Then it suddenly stopped. The same thing happened today for 2 hours until I completed the steps above.

The moral of the story is to download both Netlimiter and Networx (Freeware) and monitor your own browser traffic if you use a browser that prefetches content. You could be wasting precious bandwidth. Netlimiter will also monitor all other processes so you can narrow down other suspect traffic.

I hope this helps anyone with the same problem. I’ll be looking at a big excess bandwidth bill next month (around £45) which will be a big blow to our budget.

Posted on April 18, 2012 at 9:06 am by Grumpy Git · Permalink
In: Internet · Tagged with: , , , , , ,

10 Responses

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  1. Written by marty
    on 01/08/2012 at 9:38 am

    truely helpful..TNK U

  2. Written by yaser
    on 26/11/2012 at 3:28 pm

    That was a great aid for me. Thanks a lot

  3. Written by Ryezen
    on 01/05/2013 at 5:01 pm

    Anyone figured out how to do this with the latest Chrome? I couldn’t find anything even close to the pre render option.

  4. Written by Grumpy Git
    on 06/05/2013 at 12:40 pm

    Goto Settings >> Show Advanced Settings and then under “Privacy” uncheck:

    Use a prediction service to help complete searches and URLs typed in the address bar

    Predict network actions to improve page load performance

    Job done 🙂

  5. Written by Ent
    on 04/09/2013 at 12:32 am

    Brilliant and thanks. The best advice comes from grumps not the “perky” people with rose coloured glasses.

    Email sent to Chrome letting them know what I think of their default settings.

  6. Written by Emir
    on 17/11/2014 at 4:00 pm

    i use latest version of chrome and i can’t find those option

  7. Written by Darlene
    on 28/08/2015 at 2:47 am

    Wow, thank you so much! This is exactly the problem I’ve been having for two months. Your explanation is very well stated on how all this prefetching and prerendering works.
    Thank you.

  8. Written by Casey
    on 29/04/2017 at 12:16 pm

    What the hell is prefetching

  9. Written by Aman Dudeja
    on 14/07/2017 at 7:49 am

    Job done for me:) Thank you

  10. Written by Manish Kumar
    on 10/03/2021 at 4:05 pm

    How to do this same thing in 2021?

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