If you look at , there are quite a few bugs and feature requests that have never gotten resolved. I ran into one just now in an answer I posted. The last update to the code repo (https://github.com/andrewphoy/chess-replayer) was 7 years ago and seems abandoned.

I propose using the new lichess embedded pgn viewer (https://github.com/lichess-org/pgn-viewer) instead, to get a more featureful viewer while still being lightweight.

However, the previous viewer was MIT licensed while this is AGPL-3.0. I'm not sure what the Stack Exchange policy for embedded content is.

  • For the record, the issue you encountered, it is not a bug. The replayer is not built to detect checks. You must exactly specify which knight is to move there. For example, the replayer is allows castling through an attacked square: chess.stackexchange.com/questions/24112/… Commented Sep 19, 2022 at 7:05
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    Please do not edit my original posts to change my context. That's what the answers or comments are for. It is a bug if you consider not replaying a valid PGN.
    – qwr
    Commented Sep 19, 2022 at 7:08

2 Answers 2


While an upgraded replayer is a nice idea, my concern is coding out things such dummy pawns (How likely is it that a non-orthodox promotion is optimal?), moving into check, null moves, etc. Doing so would take away a fun aspects and functions of our replayer that other sites do not support.

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    Yes, we have to balance out coding custom moves with the added features/bugfixes compared to the current viewer. I lean towards replacing but that's what meta votes are for.
    – qwr
    Commented Sep 19, 2022 at 7:23

While moving away from what may be abandonware would be a good thing I think there is not enough information here to decide if the upsides outweigh the negatives. Information on, for example,

  • What is not supported in the new viewer that is in the current one?
  • What is supported in the new viewer that is not in the current one, and what benefit will they bring?
  • Will the user interface change in any way for features that are supported by both? The joy of standards is that there are so many to choose from ...
  • Will existing posts be broken? Reassurance will be required here.
  • Is it proposed to provide any guidance on how to use the viewer, especially to new users?

would be extremely useful. Without this I'm afraid my position (as a software developer) is "if it ain't broke don't fix it."

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    While we are at wanted features: A small b or w arrow or dot indicating the orientation of the board and who has the right to move. (At the moment it seems that the board points to the player who will move, without any indication. Can be overruled to standard look-from-White, but confusing nonetheless.) Commented Oct 5, 2022 at 7:33

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