How an unusual move is measured

An unusual-move alert does not use one percent for every coin. It measures the move over a window, then compares that move with the size of this coin's own earlier moves over the same length of time.

The default window is 1 hour. Other windows the product offers can be chosen instead. The default multiple is 3. It can be set from 2 to 6.

The coin's own range

For a window, earlier blocks of that same length are taken on a fixed UTC grid. The price at each block edge is the close of the finished candle that ends there. A block whose price is missing is skipped. The gap is not filled with zero, and the close is not invented.

The usual move is the root mean square of the changes between neighboring blocks that both have a price. That means squaring each change, averaging the squares, and taking the square root. The bar for this coin is that usual move times the multiple, and it is never under 0.5%. A smaller move is not treated as unusual. That keeps a coin that barely moves from alerting on a very small change.

How much history

• 15 minutes. Up to 672 moves, spanning 7 days. At least 336 of those moves need a price.
• 1 hour. Up to 336 moves, spanning 14 days. At least 168 of those moves need a price.
• 4 hours. Up to 180 moves, spanning 30 days. At least 90 of those moves need a price.
• 24 hours. Up to 30 moves, spanning 30 days. At least 15 of those moves need a price.

If fewer than the minimum moves have a price, the check does not call the move unusual. It waits until enough history is stored. The bar stays fixed for a UTC hour, then it is computed again.

The move itself

The move is the latest price compared with the price at the start of the window. That start price is the close of the finished candle at the window boundary. If that candle is missing, we also try 2 minutes before it. If those minutes are missing too, the check has no answer and does not fire.

The alert fires when the absolute move is at least the bar. After it fires, it can arm again when a full window has passed, or when the move has fallen under 50% of the bar. The usual wait before it can fire again is 4 hours.

A missing price is never read as zero. The price page says when a price is too old to use.

Updated October 12, 2026.