Debugging

Express Rate Limit supports debug logging similar to Express via the debug library.

Basic debugging

To see all the internal logs from Express Rate Limit, set the DEBUG environment variable to express-rate-limit when launching your app:

$ DEBUG=express-rate-limit node index.js

On Windows, use the corresponding command:

> $env:DEBUG = "express-rate-limit"; node index.js

Running this command on a basic configuration prints output similar to the following at instance creation:

$ DEBUG=express-rate-limit node server.js
  express-rate-limit creating new rate limiter with 'MemoryStore' +0ms
  express-rate-limit set windowMs to 60000 +0ms
  express-rate-limit set limit to 5 +0ms
  express-rate-limit set message to 'Too many requests, please try again later.' +0ms
  express-rate-limit set statusCode to 429 +0ms
  express-rate-limit set legacyHeaders to true +0ms
  express-rate-limit set identifier to [Function: identifier] +0ms
  express-rate-limit set requestPropertyName to 'rateLimit' +0ms
  express-rate-limit set skipFailedRequests to false +0ms
  express-rate-limit set skipSuccessfulRequests to false +0ms
  express-rate-limit set requestWasSuccessful to [Function: requestWasSuccessful] +0ms
  express-rate-limit set skip to [Function: skip] +0ms
  express-rate-limit set keyGenerator to [AsyncFunction: keyGenerator] +0ms
  express-rate-limit set ipv6Subnet to 56 +0ms
  express-rate-limit set handler to [AsyncFunction: handler] +0ms
  express-rate-limit set passOnStoreError to false +0ms
  express-rate-limit set standardHeaders to false +1ms
  express-rate-limit set store to MemoryStore { validations: { default: true, validationsConfig: false, knownOptions: false, draftPolliHeaders: false, onLimitReached: false, keyGeneratorIpFallback: false, ipv6SubnetOrKeyGenerator: false }, previous: Map(0) {}, current: Map(0) {}, localKeys: true } +0ms
  express-rate-limit set validations to { default: true, validationsConfig: false, knownOptions: false, draftPolliHeaders: false, onLimitReached: false, keyGeneratorIpFallback: false, ipv6SubnetOrKeyGenerator: false } +0ms
  express-rate-limit set logger to { warn: [Function: warn], error: [Function: error] } +0ms
  express-rate-limit executing init for store +1ms

When a request is then made to the app, you will see the logs similar to these:

  express-rate-limit requested '/' +5s
  express-rate-limit request from ip '::ffff:127.0.0.1' +0ms
  express-rate-limit computed key '127.0.0.1' +0ms
  express-rate-limit incrementing count +0ms
  express-rate-limit set request.rateLimit.limit to be 5 +0ms
  express-rate-limit set request.rateLimit.used to be 1 +0ms
  express-rate-limit set request.rateLimit.remaining to be 4 +0ms
  express-rate-limit set request.rateLimit.resetTime to be 2026-07-16T09:46:11.574Z +0ms
  express-rate-limit set request.rateLimit.key to be '127.0.0.1' +0ms
  express-rate-limit set legacy headers +0ms

Other logs and advanced usage

Set the value to * to see all debug logs from Express and anything else that uses the same debug convention.

See https://www.npmjs.com/package/debug for more advanced usage.