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 | |
|---|---|---|---|
| Meme I accidentally 93MB of .rar files what should I do…is this dangerous ? |
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| ISO 12233 Chart | 
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| Lorem Ipsim Test Page |
3 Requests – 703B Transferred. |
4 Requests – 2.05KB Transferred. |
4 Requests – 1.68KB Transferred. |
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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 Skippy.org.uk where they were processed and optimised by my server for inclusion in my blog using wp-smush.it. 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
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)
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 http://1.2.3.10/bmi//skippy.org.uk/).
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.
3 thoughts on “O2 and T-Mobile on Compressing the Web.”
I would compare the images…but I’m on an o2 connection.
Their service on a phone is even more annoying, Facebook images are compressed so small I can’t read ones which have text in them.
its all good fun when that kind of thing happens;
I will talk to o2 again and see what they recommend. will also try talking to Three.
Not perfect, but quite usable: Use the Change HTTP Request Header Extension for Chrome, adding a Cache-Control: no-transform http header to all and every request.
It’s not quite straight forward to configure though. I had to supply a dummy rule (i.e. URL == bla) to get it going.