Polygon
cURL
curl is the fastest way to poke at the Polygon JSON-RPC API without pulling in an SDK — it is ideal for testing that your endpoint works, debugging a malformed request, or wiring quick checks into shell scripts and CI pipelines. Every Polygon RPC call is an HTTP POST carrying a JSON body, so each request needs the Content-Type: application/json header. Your API key lives in the URL path: https://polygon.therpc.io/YOUR_API_KEY. Because Polygon PoS (chain ID 137) speaks the standard Ethereum JSON-RPC dialect, the same method names you know from Ethereum — eth_blockNumber, eth_getBalance, and the rest — work here unchanged.
You can authenticate to Polygon in two ways: place the key directly in the URL path (https://polygon.therpc.io/YOUR_API_KEY), or send it as a Bearer token in the Authorization: Bearer YOUR_API_KEY header. Either way, every request to the Polygon endpoint must be a POST with Content-Type: application/json.