Playing online

• https://minesweeper.online/ - This website offers various features such as user accounts, game statistics, and game replays as animations. It also has a no guessing mode (minesweeper without need to guess).

Probability calculators

These calculators allow you to input a board and automatically calculate the probabilities of cells being mines or safe, or even the probability of winning.

• https://mzrg.com/js/mine/probability.html - This calculator computes the probabilities of cells being mines. Use the [Edit] mode to create a board, then click "Compute Probabilities". You can then use the [View] mode to see the probabilities.
• https://davidnhill.github.io/JSMinesweeper/ - This calculator computes the probability of cells being safe. It also uses heuristics to choose the best cell based on not only the probability of it being safe, but also on the potential progress that uncovering that cell can provide. When there are few possible board positions, it attempts to find the best (perfect) guess by calculating the exact win probability.
• https://github.com/DavidNHill/Minesweeper - The same as above but requires downloading. It is faster than the online version but appears to be less maintained.

Efficiency and ZiNi calculators

In short, ZiNi is a number, that tries to find the minimum amount of clicks needed to solve a specific board with allowed use of flags and chords. ZiNi calculators allow you to input a board and attempt to find its ZiNi value.

• https://pttacgfans.github.io/Minesweeper-ZiNi-Calculator/ - This is a good ZiNi calculator that provides an animation of the best solution it finds.
• https://mzrg.com/js/mine/make_board.html - This calculator allows you to create boards and calculates their ZiNi values, among other things.

Misc

• https://mzrg.com/js/mbm/ - Minesweeper Board Museum. This site shows off several dozen important, unique, or interesting Minesweeper boards, such as Densest Solvable Boards.