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ipKeyGenerator(ip, ipv6Subnet=56)

Params:

  • ip (string) An IPv4 or IPv6 IP address
  • ipv6Subnet (number|false) Subnet mask to apply to IPv6 addresses. Valid range is 1-120, recommend range is 48-64.

Returns: (string) IPv4 address unchanged, or IPv6 network address in CIDR notation. (Unless second parameter is false, then IPv6 is also returned unchanged).

This method is used by the default keyGenerator to apply the configured ipv6Subnet, in order to properly rate-limit IPv6 users.

When using a custom keyGenerator that uses the user’s IP for rate-limiting (even as a fallback), return the result of this method rather than the IP address itself.

import { rateLimit, ipKeyGenerator } from 'express-rate-limit
const limiter = rateLimit({
	// ...
	keyGenerator: (req, res) => {
        // use userID for authenticated users
        if (userIsAuthenticate(req)) {
            return req.userId
        }
        // fall back to IP address for unauthenticated users
        // use ipKeyGenerator to apply a /56 subnet to IPv6 users (IPv4 returned unchanged)
        return ipKeyGenerator(req.ip, 56)
    },
})