Fee Rate (P99) shows the 99th-percentile fee rate paid by Bitcoin transactions on a given day, in sat/vB. Ninety-nine percent of transactions paid this fee rate or less, so the series isolates the extreme edge of the block-space bidding market.
A rising P99 means the most aggressive transactions are paying materially more for inclusion. If P99 pulls away from P90 and the median, urgency is concentrating at the extreme tail rather than across the full market. It belongs beside Median Fee Rate and Fee Rate (P90).
The key caveat is extremity. P99 is not a read on typical conditions, and by itself it can exaggerate how stressed the broader fee market was. Its job is diagnostic: it shows what happened at the sharpest edge of urgency.
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