# Challenges

BotStopper supports these challenge methods. Each page describes the method and its configuration.

- [fast](/docs/challenges/fast.md): optimized proof of work with multiple threads.
- [argon2id](/docs/challenges/argon2id.md): memory-hard proof of work.
- [hashx](/docs/challenges/hashx.md): proof of work with a generated hash function.
- [preact](/docs/challenges/preact.md): a lightweight browser challenge.
- [meta-refresh](/docs/challenges/meta-refresh.md): a browser refresh after a delay.
- [soteria](/docs/challenges/soteria.md): proof of work with an obfuscated virtual machine.

Use [thresholds](/docs/configuration/thresholds.md) to select challenges from request weight.
Use [extensions](/docs/extensions.md) to add checks to a challenge.