With Kvetka you can use any chess engine which supports UCI format. Nowadays UCI is the most popular protocol for interacting between the chess engines and their graphic interfaces. It replaces format Xboard/Windboard. There is also a closed commercial format used by the company ChessBase but nowadays only Fritz is still tied to its graphic shell and doesn't have its UCI version.
The authors are constantly developing their engines, therefore from time to time the title of being strongest is transferred from one engine to another. Here you can see the list of the top engines according to CCRL, one of the most prestigious rating lists. The other two popular engines rating lists are CEGT and IPON.
- StockFish - The strongest engine for today (beginning of 2017). Version 8 is provided together with Kvetka.
- Houdini 1.5 - the last free version of the Houdini engine.
- Rybka 2.232 – "Rybka" version which becomes free after Rybka 3 release.
- List of free UCI-engines, sorted by their ratings (currently outdated).
- WildCat – Product from belarusian programmer Igor Korshunov.
- Fruit. Legendary engine which was the strongest some time ago. It is programmed by Fabien Letouzey from France. Nowadays it is outrun by a number of other engines.
- Komodo – it was the strongest engine about a year ago. Now (beginning of 2017) it goes third.
- Houdini – several times it was the leading engine. After a couple of years break it again came on top of the list with the second result.