In short, I am looking for an online free chess engine that has either: a.) multiple engines with multiple ratings, some as low as 1500-1600, and some as high as 2200 or better, or b.) is a single engine with adjustable difficulty ratings from about 1500-1600 and up.

To clarify, someone once recommended that when playing alone against the computer, I should find a difficulty setting that I can beat roughly 2/3 of the time, and another that I can beat only about 1/4 of the time. Of course I'd rather play OTB (the best practice) but life/job/family commitments don't allow for too much of that these days.

I can readily beat Microsoft's Chess Titans at all levels, including level 10 (or I should say I can beat it at least 3 out of 4 times). Thus, Chess Titans doesn't fit the bill of being able to beat me somewhat more often. I realize that most purchasable standard chess software has adjustable ratings, but I don't feel like buying any right now.

Lastly, I am aware that Elo ratings for chess engines are a fuzzy subject -- given that they don't make the same kinds of blunders that real humans do, don't give up, play at different levels in different situations, etc. I am not demanding a highly specific rating. I merely would like to vaguely know the general level of my computer opponent while I play.

At any rate, any recommendations for a free online chess engine with adjustable difficulty levels, whose elo ratings are roughly known?

  • 1
    Why do you need to play against computers specifically? If you feel like you want to play, but don't feel like you have a lot of time to play OTB, you could always play online on some server(ICC and the free FICS are both wonderful). This cannot possibly be more time consuming than playing against a computer.
    – Scounged
    Sep 23, 2015 at 14:38

7 Answers 7


http://www.computerchess.org.uk/ccrl/4040 gives you a huge list of engines with their CCRL rating. Please note CCRL rating is not directly related to the human FIDE rating, but it's a reasonable estimate in any case.

I recommend you my engine apps. They're free and very popular. Please visit my site to try my chess apps:


You'll find a Stockfish app with adjustable playing strength. You'll also find my own chess engine in the SmallChess app. There is also a Chess Mini app, that plays interesting chess at around FIDE 1800 to 1900. Apart from simply just playing, you'll also receive useful feedback, for example:

enter image description here

It's obvious the great Nimzowitch had been winning most of the game. The graph will tell when and how you blunder.

Now, back to the rating. While the SmallFish app (Stockfish engine integrated) allows adjustable playing strength, the rating reported in the app isn't very accurate. The confidence interval is roughly about +-200 Elo. The rating range given in the SmallChess app is much more accurate, because I'd paired it against human players on the FICS server.

I'm sure you'll learn and improve your chess by playing my apps.

  • Thank you guys. This answers my question. I will look in to all of the links provided above, and will strongly consider investigating the app above. @StudentT - nice to meet another programmer. Although I teach High School these days, I have a strong background in computer programming, and have considered developing a number of apps on a number of occasions. Looks like you have beat me to the punch on several ideas! Great job!
    – Brent
    Jul 25, 2015 at 17:46
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    Please consider to accept the answer if it helps.
    – SmallChess
    Jul 26, 2015 at 13:06
  • Please check the URL. Is shows double ":" in the URL of smallchess.com
    – Rogier
    Jul 27, 2015 at 4:55

You could use lichess which uses stockfish chess engine.

The difficulty AI levels varies from 1350 to 2400.


If you download an UCI like Arena, it is posible to install a lot of free engines and some of them are adjustable in terms of ELO (or the equivalent in computers). I've found this very helpful. In the menu Levels - Limit Playing Strenght to ELO, is posible to tweak the ELO almost by 1 point at a time.

Here you have some of the Engines I have installed, with the respective ELOs: MadChess 400-2000 Rodent 600-2600 Ufim802 700-2000 Cheng 800-2500 Deuterium 1000-2800 Spike 1100-2500 Rybka 1200-2400

Note: Some of this ELOs are not very accurate, but I think the margin is around 80-100 points. MadChess and Rodent are my everyday engines and I found them pretty consistent.

Hope this help!


Lucas Chess is a free program for Windows which includes 36 engines with ratings ranging from 600 to 3000. It also has a bunch of tactical puzzles and training features.


Nagaskaki is also free and for Windows, and has ten or so levels ranging from 1472-2300.

For iOS or Android, there is also Remi Coulon's The Chess Crazy Bishop which is free and has 100 levels ranging from 258-2300.

I should note that Stockfish (Smallchess), Lucas Chess and Chessmaster even when set at low levels will mix in stretches of extremely strong moves, and then throw in the occasional blunder which you have to spot. This is very different from playing against a human at that rating level. Humans play slightly weaker moves generally instead of alternating ultrastrong with ultraweak. An engine with a low base rating on CCRL won't be able to throw GM level moves at you although it will still likely be stronger tactically than a human with a similar rating. Shredder is perhaps better at maintaining a consistent level when you lower its Elo than some programs. Crazy Bishop seems pretty good at this too.


None of these answers address the OP's crucial incorrect assumption that software ENGINES can have specific ratings across different hardware! If you want to know an engine's strength in any meaningful sense that's even roughly equivalent to human ratings, you have to look at the power of the hardware running the engine. A weak engine on the latest expensive high-end computer can still thrash a strong engine on a cheap computer bought several years ago.

The CCRL 40/40 list already posted attempts to standardise chess engine ratings with reference to an Athlon64 X2 4600+ at 2.4 GHz. Depending on the hardware you're using to run your software engine, the actual playing strength of your engine could be completely different: even the relative strengths may change (i.e. you can't guarantee that engine A's beating engine B on different hardware means it will still win on your hardware, because different engines may benefit differently from different processors).

To get a realistic sense of your chess engine's strength on YOUR hardware, you need to enter your specific engine+hardware into a tournament against rated competitors. Otherwise, the best you can do is to use a rated system (e.g. one of the ones on the CCRL 40/40 website) as a reference point, and estimate from that (really "guesstimate", because a small difference in software engine version or computer hardware configuration can make a big and not necessarily predictable difference in actual playing strength).

  • Not correct. Strong engine on a several years ago hardware can still beat weak engine with the latest hardware. We do know computer rating could be inaccurate, but that's not the point of the question.
    – SmallChess
    Mar 10, 2017 at 3:39
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    If you don't trust me, try Stockfish 8 on a 3 years-old machine against Crafty on a new machine.
    – SmallChess
    Mar 10, 2017 at 3:43

You can find some best robots in Fics Website . Free Internet Chess Server Website FICS. There you find various Chess Robots which play from a level of 1800-2400 .

Just login to the website and you can find the machines are having a different color code to identify . Please see the link for the Chess Engines.

FICS Chess Engines


A chess program is simply a user interface with a built-in engine. Some chess programs (user interfaces) allow users to replace the engine with a different engine changing the strength of play (assuming a statistically relevant ELO rating variance). There are several great free chess programs that run solid chess engines such as Level 100 (comes with Crazy Bishop engine). Level 100 is the best free user interface/engine combo that I have used. Unfortunately, Level 100 does not allow users to replace the Crazy Bishop chess engine. There are some $60+ chess programs such as Fritz, which allow users to load other engines. I personally use Fritz 15 for its intuitive and customizable user interface. I swapped out the standard Fritz 15 engine for Stockfish 8. As others have already stated, engine performance is greatly impacted by hardware. If you are using an older machine, you will want to increase the thinking time of the computer (older computers take much longer to process alternatives). This should greatly mitigate the strength loss from using an older computer.

  • 1
    Op was looking for online engines with a known rating, not for an explanation of what a chess program is.
    – Herb
    Oct 24, 2017 at 1:55

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