Polkadot Slashing Explained

How Slashing Works on Polkadot

Polkadot enforces economic penalties to deter two classes of validator misbehaviour:

Offence TypeWhat triggers itTypical Slash SizeNotes
Unresponsiveness (offline)Validator misses > 10 % of its assigned blocks during a session≈ 0.1 % of the stake tied to that validatorConsidered a minor offence. The validator is also chilled (kicked out) for at least one era.
Equivocation (double-signing)Validator signs two different blocks for the same slot (BABE) or two conflicting votes (GRANDPA)From 0.01 % up to 100 % depending on how many validators equivocated in the same slotA major offence. Penalty scales quadratically with the fraction of validators involved

Slash-size formula (equivocation)

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slash = min((3 × x / n)^2, 1)

  • x = number of misbehaving validators
  • n = total validators in the active set

Examples:

  • 1 / 100 equivocators → min((3 × 1 / 100)², 1)0.09 % slash
  • 20 / 100 equivocators → min((3 × 20 / 100)², 1) = 36 % slash

Who Pays the Penalty?

  • The validator’s self-bond and each nominator’s bonded DOT are slashed pro-rata.
  • Only the stake exposed to that validator is affected. Nominating 16 different validators isolates risk to ¹⁄₁₆ of your bond per incident.

What Happens to Slashed Funds?

  1. Slashed DOT is immediately removed and frozen for 256 eras (~9 months).
  2. After that period: 50 % is burned and 50 % goes to the Treasury.

Chilling & Re-Entry

  • A slashed validator is chilled (removed) and must wait at least one era before re-entering.
  • Nominators are automatically re-nominated to the validator’s stash. For uninterrupted rewards, manually switch to a trusted validator.

Mitigating Your Risk

  • Distributing your stake across multiple pools

ActionBenefit
Split nominationsYou can distribute up to 16 nominations from one account, isolating slash exposure.

Key takeaway:
Slashing is rare and manageable. Choosing reputable validators like Pier Two—with proven uptime, high self-stake, and robust fail-over—greatly mitigates the risk.