otsukare Thoughts after a day of work

Opera Mini and Mobile Orientation Switching

Caleb, a former colleague, testing the Pheromone Lab Web site on Opera Mini told me: "When you switch from Portrait Mode to Landscape Mode, the page is not resized to the full width of the viewport." Indeed. Was it a bug in his CSS or a bug on Opera Mini? Neither. But first you need to understand what is Opera Mini.

Opera Mini has its main rendering engine (the software which interprets html, CSS, javascript, …) not on the mobile device but on a distant Opera server. When you type an address such as, a request is sent to the Opera Server, which is acting as a client for the Web site on The Web site sends back an answer to Opera server, which interprets it and make an OBML file. OBML stands for Opera Binary Markup Language which creates a kind of compressed image of the Web page (sometimes 90% of size reduction).

Opera Mini\ Image from A developer’s look at Opera Mini 5

When you switch the orientation of the device. Opera Mini has just an image to rotate and not the full code to reinterpret for fluid and flexible layouts. You then need to reload the pages so that it is resized for the new landscape mode of the mobile device.

If you need to test your own design with Opera Mobile and Opera Mini, go to the Developer Tools page. You will find an Opera Mobile emulator (full Browser) or the Opera Mini Simulator and the ultimate tool for debugging: DragonFly.