How to Flag in Minesweeper (and When Not To)

Flagging is the first thing most players learn after clicking, and it feels essential: mark the mines so you don't step on them. But here's the twist that surprises people. Knowing how to flag in Minesweeper is easy, and knowing when not to flag is what actually makes you faster. This guide covers both, because the mechanic takes ten seconds to learn and the judgment takes a little longer.

How to place a flag

A flag marks a cell you're certain holds a mine. The controls depend on your device:

• Desktop: right-click a hidden cell to plant a flag. Right-click again to remove it.
• Mobile and touch: tap and hold (long-press) a cell to flag it, since there's no right mouse button.

On our boards you can do both, and the how-to-play tutorial walks through the controls live if you want to see them in action. Once a cell is flagged, you can't accidentally reveal it, which is the whole point: flags protect known mines from a stray click.

What the flag counter actually tells you

The number in the corner of the board starts at the total mine count and drops by one each time you place a flag. It is tempting to read it as "mines left," but be careful: it only counts your flags, not actual mines. Flag a cell wrongly and the counter still ticks down, lying to you.

So the counter is useful, but only as good as your flags. Late in a game, when every flag is correct, it becomes a genuine logic tool. If it reads 2 and you can see where both remaining mines must be, everything else on the board is safe.

When flagging helps

Flags earn their keep in a few situations:

• Crowded areas. When several numbers overlap, marking the certain mines clears your visual field so you can read the safe cells.
• Chording. This is the big one. To chord, a number needs its mines flagged first, so flagging is what unlocks the fastest clearing move in the game.
• Endgame counting. Correct flags plus the mine counter resolve the final ambiguous cells.

If you're learning, flag freely. It reinforces the logic and keeps you safe while the deductions are still slow.

Why fast players flag less

Here's the counterintuitive part. Watch a Minesweeper speedrun and you'll see almost no flags at all. At the top level, flagging costs time, since each flag is a click that doesn't reveal anything. Elite players track mines in their head and only reveal safe cells, skipping the flagging step entirely. This is called "no-flag" or NF play, and on a timed board it's measurably faster.

That doesn't mean you should never flag. It means flags are a tool with a cost. The faster you want to be, the more you'll flag only when it directly enables a chord or untangles a mess, and skip it everywhere else.

A balanced approach

For most players, the sweet spot is in the middle:

• Flag mines that let you immediately chord a nearby number.
• Flag in genuinely crowded spots where it clears your head.
• Don't bother flagging an isolated mine you've already mentally noted, unless you're using the counter to finish.

Flagging is certainty made visible. Use it when the certainty helps you act, and skip it when it's just bookkeeping. As your reading speed improves, you'll naturally flag less without ever deciding to. For the bigger picture of how flagging fits into a full solve, see the strategy guide.