Android Netrunner Comprehensive Unofficial Rules Wiki
Page 31, Column 2, Paragraph(s) 5, Core Rule Book
Prevent effect: An effect that stops another effect from resolving.
Page 30, Column 1, Paragraph(s) 13, Core Rule Book
Avoid Effect: An effect that stops another effect from resolving.

Any ability of any type can also be a prevent or avoid ability. Prevent and avoid abilities can stop another effect from happening, and they are the only kinds of abilities that can interrupt another ability during resolution— even when the player who owns the prevent/avoid ability does not have priority— because they can only be triggered when the effect that would be prevented/avoided is resolving.[1]:Ruling[2]:Ruling

Page 21, Column 2, Paragraph(s) 8, Core Rule Book
Some card abilities use the words "prevent" or "avoid." Prevent or avoid effects are the only effects which can disrupt another effect. A prevent or avoid effect states what it is preventing or avoiding, and an effect that is prevented or avoided is not resolved. Prevent or avoid effects can be triggered whenever the effect they are preventing or avoiding is resolving.

Interaction with "Additional"[]

Prevent and avoid effects take precedence over conditional abilities triggered by the preventable effect unless that conditional ability is an "additional" ability.

Page 3, Column 1, Paragraph(s) 12, FAQ
Prevent/Avoid effects take priority over conditional abilities that would trigger from whatever is being prevented or avoided, except when a conditional ability uses the word "additional."


  1. Using Paid Abilities to Avoid Tollbooth Ruling, Question 1
    The Runner approaches a piece of ICE during a run. The Corp rezzes Tollbooth.

    The Runner has 3 credits. Can he use Net Shield or New Angeles City Hall to spend a part of his money so that he doesn't lose it all? What about using the Corroder?

    Earlier you said: "You can trash a Corporate Troubleshooter even if there is no ice protecting the server."

    So a cost can be paid even if the effect does nothing, right?

    You cannot use prevent or avoid effects unless the condition that they are preventing/avoiding is occurring. You could use a non-prevent/avoid paid ability such as on Corroder to spend 1 credit when the Corp rezzes Tollbooth. We will take another look at this scenario before releasing the next FAQ, but that is currently a valid interaction.
  2. Prevent and Avoid Ability Timing Ruling
    Can I use my sacrificial clone just to clear tags (like, post-midseasons) or is it only when you're about to take damage?
    Nope. Only use prevent/avoid to prevent/avoid.