The history of WZebra is very much the history of Zebra, the Othello engine which WZebra uses when playing. Here are some important events:
June 3, 1997
Gunnar Andersson starts working on an Othello program which he decides to call Zebra. After three weeks, it reaches a rating of 1500 on the Internet Othello Server (IOS), corresponding to an amateur human player.

August 1997
The crude evaluation function and search algorithms work properly.

September 1997
All major program components - opening book, hash table, endgame solver - implemented and debugged. The IOS rating is now 1900, stronger than most players in the World Championships.

January 1998
A new pattern-based evaluation function is tuned and debugged. The IOS rating leaps to 2300, higher than all humans.

March 1998
Midgame and endgame search are vastly improved through the use of the Multi Prob-Cut algorithm. An improved opening book algorithm is tested.

May 1998
Zebra beats Hannibal, the strongest Othello program, for the first time. The IOS rating is now above 2500, making it one of the five strongest programs in the world.

May 1998
Lars Ivansson starts working on a graphical user's interface for Zebra. He decides to call the program WZebra.

June 1998
The first version of WZebra is released as freeware.

August 1998
WZebra 1.41 is released. This is the first version without serious bugs.

October 1998
Zebra finishes 3rd in the prestigious Princeton II tournament for computer programs (winner was Hannibal and runner-up was Logistello).

Spring 1999
Zebra's search algorithms undergo a revision that gives great speedups.

July 1999
More corner knowledge is added to the evaluation function and some bugs in the evaluation function are removed.

October 1999
The IOS version of Zebra which only plays rand games, Reindeer, reaches a rating of 2932. At that point, Reindeer had the highest rating of all active players on IOS.

November 1999
WZebra 2.0 is released. Compared to earlier versions it plays stronger and has many new functions.

January 2000
WZebra 2.1, with support for the Thor database, is released.

October 2000
WZebra 2.2 is released. Compared to earlier versions, it provides a faster endgame and a stronger and larger opening book.

November 2001
WZebra 3.0 is released. It contains new features, new graphics design, and a faster Othello engine.

January 2002
WZebra 3.1 is released. It features improved graphics and new features.

May 2002
WZebra 3.2 is released. It has more features and less bugs than previous versions, and also an evaluation function which understands rare board positions better.

August 2002
WZebra and LZebra 3.3 are released. The latter is a Linux port of WZebra, both contain the same set of features.

November 2002
WZebra 4.0 is released. It contains many new features and bug fixes. Furthermore, its midgame searches are deeper.

January 2003
WZebra 4.1 is released. It has a faster endgame solver than previous versions.

April 2003
WZebra 4.2 is released. It features improved fully configurable board graphics, including a 3D mode.