OPTF2

OPTF2 is a community web-based backpack viewer built upon Steam's WebAPI platform and written in the Python programming language. While starting out as a backpack viewer for Team Fortress 2, it later incorporated the ability to see the inventories of multiple games, including Dota 2.

Front page
The front page features a message of the day and a random item from any one of the games supported by OPTF2, as well as the last ten backpacks viewed of the game the random item is selected from. In addition, the front page allows for the ability to publicly '+1' and 'follow' the website on Google+. The front page for each game is independently themed and features a random item and backpack list from that game only.

The navigation bar on the top of each page allows the user to switch between games and search for player backpacks, and also features a news feed linking to the OPTF2 development blog.

Backpacks
A player's backpack may be viewed by searching for them using either their current Community Name, or Steam URL. A small info box is displayed on the right hand side which gives statistical information such as the total and average in-game store value of the backpack, an itemised breakdown of the backpack's contents, and also features the ability to publicly '+1' the backpack on Google+. The backpack view is themed differently depending upon the game backpack being viewed.

The backpack view features a toolbar allowing the user to filter the backpack based on various parameters, including time, serial, level, name, type, class, and item quality. In addition, untradable items can be hidden from view. The backpack view toolbar also allows for the currently equipped loadout to be viewed, and allows the user to switch to the players' backpack from another game using the 'OPNet' link.

Lists
OPTF2 has various lists:
 * A list of every item in the game,
 * A list of every item attribute in the game,
 * A list of every particle system in the schema.

Source code and schema tracking
OPTF2's source can be found on its self-hosted Git tree. In addition, OPTF2 hosts a repository which mirrors and tracks changes to the WebAPI schema feeds for several Steam games. The repository is updated every five seconds.

Modular design
OPTF2 features a modular design, allowing for Steam games to have their schemas loaded with ease; this is reflected publicly as a game's module name forms the first part of the url after the domain name, allowing the user to easily switch between games by substituting that part of the url. For example, 'tf2' can be switched to 'd2b', switching the view from Team Fortress 2 to Dota 2 Beta.