Registry / http-networking / express-slow-down

express-slow-down

library3.1.0jsnpmunverified

Basic rate-limiting middleware for Express that slows down responses rather than blocking them outright. Current stable version is 3.1.0, released as part of the express-rate-limit ecosystem. It is built on top of express-rate-limit and uses its stores, providing a familiar API for slowing repeated requests. Key differentiator: it delays requests after a threshold instead of rejecting them, making it suitable for public API endpoints where gradual throttling is preferred over hard blocks. Requires Node >= 16 and Express 4/5. Ships TypeScript types, supports ESM and CJS, and is actively maintained.

http-networking auth-security web-framework

npm install express-slow-down

github ↗package ↗

INSTALL

IMPORT

SIG · EXPRESS-SLOW-DOWN

express-slow-down

http-networkingjavascriptv3.1.0

Install

—

Import

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Disk

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Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

slowDown

✓ import { slowDown } from 'express-slow-down'

✗ import slowDown from 'express-slow-down'

This package exports a named export 'slowDown', not a default export. The wrong pattern is common when migrating from older versions or confusing with similar libraries.

slowDown

✓ const { slowDown } = require('express-slow-down')

✗ const slowDown = require('express-slow-down')

In CommonJS, destructure the named export. Doing require('express-slow-down') directly yields an object with the named export.

slowDown (TypeScript)

✓ import { slowDown } from 'express-slow-down'

✗ import { SlowDown } from 'express-slow-down' (wrong case)

The exported function is lowercased 'slowDown'. TypeScript types are included, but the export name is case-sensitive.

Creates a speed limiter middleware that delays requests after 5 hits within 15 minutes, adding incremental delay.

import { slowDown } from 'express-slow-down'; import express from 'express'; const app = express(); const speedLimiter = slowDown({ windowMs: 15 * 60 * 1000, // 15 minutes delayAfter: 5, // allow 5 requests per 15 minutes without delay delayMs: (hits) => hits * 100, // add 100ms delay per hit after the 5th }); app.use('/api', speedLimiter); app.listen(3000);

Debug

Known issues

breakingVersion 3.0.0 removed the default export; use named export 'slowDown' instead.

fix

Change `import slowDown from 'express-slow-down'` to `import { slowDown } from 'express-slow-down'`.

affects: >=3.0.0

breakingVersion 2.0.0 dropped support for Node < 16 and changed the API from `delayMs` as a number to a function.

fix

Update `delayMs` to be a function returning the delay in ms, and ensure Node version >= 16.

affects: >=2.0.0 <3.0.0

gotchaWhen using both express-rate-limit and express-slow-down with the same external store, you must create two separate store instances with different prefixes to avoid double-counting.

fix

Create separate store instances: `const store1 = new MemcachedStore({ prefix: 'rl:' }); const store2 = new MemcachedStore({ prefix: 'sd:' });`

affects: *

deprecatedThe 'skipFailedRequests' option has been deprecated in favor of 'skip' function.

fix

Use the 'skip' function with a custom check instead of 'skipFailedRequests'.

affects: >=2.0.0

Errors

Common errors & fixes

import slowDown from 'express-slow-down'; ^^^^^^^^ SyntaxError: The requested module 'express-slow-down' does not provide an export named 'default'

Trying to default-import the module, but version 3.x only provides named export 'slowDown'.

fix

Use named import: `import { slowDown } from 'express-slow-down'`

TypeError: slowDown is not a function

Using `require('express-slow-down')` and calling the result as a function, but it exports an object with 'slowDown' method.

fix

Use: `const { slowDown } = require('express-slow-down')`

Error: The 'delayMs' option must be a function that returns a number. Received number.

Passing a static number for `delayMs` in version 2+, where it must be a function.

fix

Replace `delayMs: 1000` with `delayMs: (hits) => hits * 1000` or similar function.

Error: The 'store' option must be an instance of a store that implements the 'Store' interface.

Passing a plain object as a store without implementing all required methods.

fix

Use a store from express-rate-limit's compatible stores (e.g., rate-limit-memcached) or implement the Store interface.

Upgrade

Version history

3.1.0latest on npm

Audit

Dependencies

expressrequiredPeer dependency: the middleware works as an Express middleware and requires Express 4 or 5.

Agent activity

17 hits · last 30 days

node

OpenAI (training)

Resources

githubhttps://github.com/express-rate-limit/express-slow-down ↗

packagehttps://www.npmjs.com/package/express-slow-down ↗