T-Mobile’s image compression

I’ve been using a T-Mobile UK connection through a Nexus One to stay online in Blighty. It turns out that they employ some shenanigans to keep their bandwidth costs down.

A few tricks seem to be happening:

  • A transparent proxy loads your requested images, but sends you a more compressed version of your image instead.
  • On every pageload, a script tag to insert this javascript file is injected into the page header. This file allows a user to request the full quality images with a keyboard shortcut after pageload. Instructions are given with a tooltip on every image.
  • All unnecessary formatting is removed from the page source, i.e. spacing, tabs and so on from the HTML.

Here’s what the compressed image looked like:

Here’s what the original image looked like:

How much bandwidth did this save?

Here’s what we know.

  • In my very non-scientific testing, the extra compression seemed to approximately halve the size of the image delivered.
  • According to the YUI people, average image pageweight is around 50% due to images.

Therefore, T-Mobile should be saving around 25% on every pageload. This comes at the cost of a slightly diminished user experience for users, maintenance costs for the proxy and script files (albeit minimal), and potential subtle brand damage (a user might perceive T-Mobile delivered internet as worse quality).

Update: You can disable the image compression by visiting http://accelerator.t-mobile.co.uk/ while connected via t-mobile.






3 responses to “T-Mobile’s image compression”

  1. Dave Linsalata

    Nice post. Sprint does something similar with their SmartView software for their Sprint WAN cards. The software either downgrades the images or, if you’d prefer, completely prevents them from loading and taking up your (and their) bandwidth.

  2. I saw this happen when using a Vodefone 3G card a few years ago.

    If you’re on a plan whereby you pay per MB then great.

    I think it stinks if you’re on a mobile and you’ve paid for an unlimited data plan. When browsing on a mobile device every pixel counts and so I don’t want to see an image *re*-compressed. The amount of digital noise just looks horrible.

  3. Will

    You absolute genious! That proxy has been bugging me for years! Now at last I can disable or tame it!

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