The Random Thoughts of a Geek heading for Banbury
The Random Thoughts of a Geek heading for Banbury

O2 and T-Mobile on Compressing the Web.

We have known for a while that O2 compress and manipulate the internet connection that they offer to their mobile internet users.

For this test I am using the The ISO 12233 Target, and a randomly mildly ammusing mame I found online. The ISO 12233 target was developed for digital camera applications. It includes several diffrent patterns, and knife-edge targets.

Direct Conection O2 Mobile Internet T-Mobile
I accidentally 93MB of .rar files
what should I do…is this dangerous ?
  • I-accidentally-93mb.jpg – 30.25KB (29.95KB)
  • I-accidentally-93mb.jpg – 8.88KB (8.60KB)
t-mobile I accidently
  • I-accidentally-93mb.jpg – 9.43KB (9.16KB)
 ISO 12233 Chart  
  • ISO_12233-reschart.jpg – 4.14MB (4.14MB)
  • ISO_12233-reschart.jpg – 4.14MB (4.14MB)
  • ISO_12233-reschart.jpg – 4.14MB (4.14MB)
Lorem Ipsim Test Page
  • Loremipsum.html – 205B (2.50KB)
  • grey_120x240.gif – 221B (4.63KB)
  • valid-xhtml10 – 277B (1.84KB)
3 Requests – 703B Transferred.
  • Loremipsum.html – 1.63KB (2.59KB)
  • bmi.js – 372KB (13.84KB)
  • grey_120x240.gif – 4.90KB (4.63KB)
  • valid-xhtml10 – 2.30KB (1.84KB)
4 Requests – 2.05KB Transferred.
  • Loremipsum.html – 205B (2.61KB)
  • bmi.js – 372KB (13.84KB)
  • grey_120x240.gif – 188B (4.63KB)
  • valid-xhtml10 – 282B (1.84KB)
4 Requests – 1.68KB Transferred.

Direct Connection

This was via a fixed line broadband connection, and was used as the control, the images were originally downloaded and then re-uploaded to where they were processed and optimised by my server for inclusion in my blog using the following actions are applied to all images on my server (under 1mb):

  • JPEGs have meta data stripped
  • optimizing JPEG compression
  • certain GIFs are converted to indexed PNGs
  • stripping the un-used colours from indexed images
Most images are about 2-20% smaller after the lossless optimisation than they were before; with no loss of image quality, this may not seem like a lot; but its better than not carrying out the acctions, and already goes some of the way to optimising my sites for mobile transfer, however as we can see from above Mobile internet providers feel the need to edit them further.

O2 Connection

This test was carried out using my O2 Simplicity contract; using my tethered iPhone (I wonder if it would have been different using my unlocked 3G modem (It is not called it a dongle!)).

The actions that O2 carry out on my request include:

  • Lossey Compress of images
  • Remove white space from HTML files,
  • Add bmi.js to requests
  • Addition of the Shift+R / Shift+A mouse over (may be from bmi.js)
I am not sure why they haven’t appeared to have touched the ISO12233 chart; perhaps because its as optimised as it can be, and due to the file size they don’t optimise it as they assume that I want it at full resolution.

T-Mobile Connection

This test was carried out using B0atG1rl’s T-Mobile G10431 3G mobile modem,

T-Mobile perform the following actions on the data I request from the internet:

  • Same as O2
  • Cache images (images are served from their cache at

Again T-Mobile didn’t touch my ISO12233 chart.

What this means?

Well to me it means that the internet I am seeing when I use mobile broad band is not the internet I requested; apparently Three don’t do this; I will be talking to a number of customer service departments, and will write up another post with my further findings.

Leave a comment

Your email address will not be published.

3 thoughts on “O2 and T-Mobile on Compressing the Web.”