HMAC SHA-256 Generator Online (Free, Private)
Generate HMAC-SHA256 signatures for API webhooks and authentication. Runs locally in your browser — secret keys never uploaded.
HMAC (Hash-based Message Authentication Code) combines a secret key with a message to produce a signature. APIs like Stripe, Shopify, and GitHub webhooks use HMAC-SHA256 so receivers can verify requests were not tampered with.
HMAC vs plain hash
A plain SHA-256 hash of a message can be recomputed by anyone who knows the message. HMAC requires the secret key — only parties with the key can produce or verify the signature.
Never upload your secret key
Server-side HMAC tools receive your API secret on their servers. Utilio computes HMAC-SHA256 entirely in your browser using the Web Crypto API.
Generate HMAC-SHA256 →