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Regex API Validation cheat sheet

Use regex safely for request validation without blocking valid users.

Quick lookup

anchorsCheck exact spelling, casing, and the platform documentation for this field.
unicodeCheck exact spelling, casing, and the platform documentation for this field.
length limitsCheck exact spelling, casing, and the platform documentation for this field.
catastrophic backtrackingCheck exact spelling, casing, and the platform documentation for this field.

Common mistakes

  • Debugging the client before checking the raw request and response
  • Ignoring headers that explain cache, auth, or rate limits
  • Treating browser CORS failures as generic API downtime
  • Logging tokens or webhook secrets while troubleshooting

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