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The only 7 piece site I heard about is http://tb7.chessok.com/ , and upon registration I am able to setup various positions with 2-6 pieces . However as soon as I setup a position with 7 piece, I get an error about service not being avaiable. Has anyone had better luck or know of any other site with 7 pieces tablebases?

Update: in the end I discovered that FinalGen solved a vast majority of positions I was interested in, included those with more than 7 pieces. http://finalgenchess.ovh/home_ing.php

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  • 1
    possible duplicate of What is the status for seven man end game table bases?
    – RemcoGerlich
    Apr 12, 2014 at 18:40
  • I had looked for a dup, but somehow missed that question... My emphasis is on FREE though. Is it correct to assume that chessok site only provides free access to 6 pieces and less, while 7 pieces require a license key?
    – Joe
    Apr 13, 2014 at 4:41
  • As far as I know, yes. I think they're the only ones who've made 7 piece tablebases, and as they take 140TB storage space, I think they'd like to have some return on their investment.
    – RemcoGerlich
    Apr 13, 2014 at 11:50
  • @RemcoGerlich fair enough; but if that's the case I wish it was made clear on their website what part is free, and what part is not; the error message that shows up when I add the 7th piece seems rather cryptic.
    – Joe
    Apr 13, 2014 at 19:37
  • 1
    mtu-media.com does not exist
    – M.M
    Feb 26, 2016 at 9:05

4 Answers 4

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Original Answer:

7-men Lomonosov is free as an Android application.

Update - September 2018:

7-men Syzygy is available for free. Also available from Lichess.

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  • 2
    Yes, you don't need a license key to probe 7 piece positions with the app!
    – Brent Baccala
    Jan 30, 2016 at 3:49
  • The comments on the Google Play store seem to indicate that the app no longer works. I can't verify that since I don't yet have an Android device.
    – rajb245
    Feb 6, 2020 at 15:56
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http://chessok.com/?page_id=27966

History Note

The first ending tablebases - for all 4-piece endgames - were built by the end of the 80-s. In the beginning of the 90-s, the same task was done for 5-pieces. In 2005, 6-piece endings were solved in Nalimov Tablebases which are now used by many professional chess programs and services.

Experts didn’t expect 7-piece endings to be cracked and catalogued until after 2015, but Convekta Ltd, namely programmers Zakharov and Makhnichev - the developers of the Aquarium interface - managed to solve this task in just 6 months using a new algorithm designed specifically for this purpose and run on the Lomonosov supercomputer based in the Moscow State University. Lomonosov Tablebases

As a result, we now have 525 tablebases of the 4 vs. 3 type and 350 tablebases of the 5 vs. 2 type. The calculations for 6 pieces playing against a lone king weren’t done because the outcome is rather obvious.

The total volume of all tablebases is 140 000 gigabytes, which is obviously too much for personal computers. Lomonosov Tablebases will be accessible online from the Aquarium interface and on the chessok.com website. All users of ChessOK Aquarium, Houdini Aquarium and Chess Assistant products get free access to the service for the period specified in their product description.

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The 7 piece EGTB is not yet freely available online, as far as I know. Building the tablebase is costly in time and resources and the storage space is not cost-free either.

Concerning http://tb7.chessok.com/ do not be too disappointed, because they mention this explicitly (at least today, maybe not on April 11th when you tried):
"Currently the tablebases are only accessible by legal owners of Chess Asssitant 14, ChessOk Aquarium 2014 or Houdini 4 Aquarium. Later, more users will be able to use the service."

And on their signup page:
" After registration you will be able to:
probe 6-man ending tablebases;
(...)
probe 7-man tablebases (license key required – see the next page)."

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https://syzygy-tables.info/ allows to look up 7-men endgame positions. It does not give DTM information for 6- and 7-men endgames, only DTZ50+. On one hand, it is compliant with 50-move rule, OTOH, DTZ50-optimal play can be ugly (if it is possible to push a pawn or sacrifice a piece, it will).

Also available for download: https://tablebase.lichess.ovh/tables/standard/

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