Charles Proxy — Free SSL Certificate Generation API (No Key)

TL;DR

This Charles Proxy API generates SSL certificates on the fly for debugging and testing purposes. Generate CA root certificates and domain-specific certificates for HTTPS traffic inspection. Each request returns a PEM-encoded certificate and private key. Useful for developers setting up local HTTPS environments, reverse proxies, or testing SSL configurations. Simple GET request, no authentication, instant PEM output.

Quick start: https://charles.fly.dev/ca

No API key needed — just make a request!

How to Use This API

1. Get CA Root Certificate

https://charles.fly.dev/ca

2. JavaScript — Fetch CA Certificate

fetch('https://charles.fly.dev/ca')
  .then(r => r.text())
  .then(pem => {
    console.log('CA Certificate (PEM):');
    console.log(pem.substring(0, 200) + '...');
  });

3. Python — Save CA to File

import requests

# Download the CA root certificate
pem = requests.get('https://charles.fly.dev/ca').text

# Save to file
with open('charles-ca.pem', 'w') as f:
    f.write(pem)

print(f"Saved CA certificate ({len(pem)} bytes)")
print(pem[:300])

Generate CA cert: https://charles.fly.dev/ca

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Frequently Asked Questions

What endpoints are available?: /ca — Get the CA root certificate in PEM format. /cert/{hostname} — Generate a certificate for a specific hostname (may require additional setup).
What format are the certificates?: All certificates are returned as PEM-encoded text, including the BEGIN CERTIFICATE and END CERTIFICATE markers.
Can I generate certs for any domain?: The API generates certificates for the specified hostname. These are intended for local development and testing, not production use.
How long are the certificates valid?: Generated certificates are typically valid for a limited duration (days to months) suitable for temporary development and testing environments.
Is this affiliated with Charles Proxy?: This is a standalone utility service inspired by Charles Proxy's SSL proxying functionality. It generates compatible certificates for use with proxy tools.
Are there usage limits?: As a free development tool hosted on Fly.io, reasonable usage is expected. For high-volume certificate generation, consider running your own CA locally.

API Details

API URL: https://charles.fly.dev
Documentation: charles.fly.dev
Category: Developer Tools
Authentication: Not Required
Geographic Coverage: Global

What You Can Build

Local development proxy with on-the-fly SSL certificate generation
HTTPS testing tool for validating SSL configuration and handshakes
Reverse proxy setup with trusted self-signed certificates for staging
API mocking service with HTTPS endpoint simulation for QA teams
Wireless debugging setup for mobile app HTTPS traffic inspection