What goes into the signing message?
The official authentication guide specifies timestamp + HTTP method + full request path. The timestamp is in milliseconds. The cryptographic signature and authentication headers must still be produced in your own client.
The request URL and signing path are different
Kalshi's environment documentation excludes the host and query from the signed path. This helper preserves the query in the displayed request URL, adds the Predictions API prefix once, and shows the text used for signing. It does not verify endpoint existence or account access.
Use a fresh timestamp when sending
The initial timestamp is a fixed example for reproducible comparisons. Use the current-timestamp button when inspecting a new request, and generate the timestamp again immediately before signing and sending in your actual client. Keep the header timestamp and message timestamp identical.
Continue with the setup guide
Read the Kalshi API-key setup guide for credentials, environment alignment and troubleshooting. The general API guide covers public market data and rate limits.