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How much weaker is the free Ethereal than its commercial version ?

Thank you to a reader nicknamed Anthuk for all the games between the free and commercial versions of the Ethereal chess engines.

After the release of the commercial Ethereal 14.00, I received inquiries as to whether it was worth it to use the free version of this chess engine, when there are many other alternative engines that have great strength.

Before answering this question, let's look a little into the past and recall what Ethereal's engine was before its commercial version appeared.

The author, Mr. Andrew Grant, has spent years developing his engine, which has become increasingly powerful, while making its source code available under the GNU GPL 3 license.

Ethereal has developed a very good reputation as a free chess engine that plays at a similar level to its commercial counterparts.

Undoubtedly, the open-source Ethereal has contributed to the spread of knowledge about chess engine development. Many authors have used and continue to use the ideas and are inspired by the way Ethereal is written.

Over the years, Mr. Andrew Grant has implemented the so-called Hand Craft Eval (HCE) in his engine with great dedication and knowledge of the matter, which has been one of the most important factors influencing the strength of the Ethereal plays.

The free Ethereal, which does not use a neural network, is in my opinion one of the few chess engines with peak HCE capabilities.


In that example, Ethereal 13.50 (without a neural network) plays white against Lc0 0.29.0 (black), the latest incarnation of the super-powerful chess engine.

A fascinating, dynamic and unbalanced position. Both sides have their chances for success. White's king, deprived of cover, is exposed to attacks, although his pawns are already very advanced and near the promotion line. Black can turn on his heavy figures at any time with the Queen and rooks in the lead.


Ethereal accepts the challenge.


Whites do not lack courage backed by a good position evaluation (HCE).

The White King has no protection? Ok, then let's create it.


27. Qc3!

Ethereal is consolidating its forces.


An impressive move in a very complicated position.


Lc0 correctly calculating does not accept the sacrifice of the white Bishop. What follows is a series of moves - maneuvers.


White's bishop is relentless. Another sacrifice that black should not accept this time either.


This one only Bishop, will probably "dream at night" Lco ;)

Ethereal takes total control of the game.


A beautiful sacrifice of the white Queen. In the next move, she will be reborn.

The game ends with the black King's mate. Ethereal wins in magnificent style against a very strong opponent.