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JWKS Builder

Convert public PEM/X.509 keys into a JWKS document with kid, use, and alg for local OIDC mocks.

Crypto & Certs
Privacy: 100% Client-Side. Your data never leaves this browser tab. Processing uses Web APIs and client-side libraries only.

Convert public PEM / X.509 / JWK keys into a .well-known/jwks.json document with configurable kid, use, and alg — ideal for local OIDC mocks.

Key #1

What is a JWKS?

A JSON Web Key Set (JWKS) is an array of public keys published at /.well-known/jwks.json so clients can verify JWTs. Local OIDC development often needs a hand-built JWKS from PEMs exported by openssl or cloud consoles.

This tool converts one or more public PEMs / certificates into a standards-shaped JWKS, optionally setting kid, use (sig/enc), and alg — all in the browser.

How to use this tool

  1. Paste a public PEM or X.509 certificate (add more keys as needed).
  2. Set kid / use / alg or leave kid blank for a SHA-256 thumbprint.
  3. Build and copy the jwks.json for your mock authorization server.

Frequently asked questions

Are private keys supported?

Only public material is included in the JWKS. If you paste a private JWK, private fields are stripped before export.

Is my data sent to a server?

JWKS Builder runs 100% in your browser. Inputs stay on your device and are not logged or stored by stbox servers.