# Upstash Ratelimit JS

> Rate limiting for serverless and edge apps with the @upstash/ratelimit TypeScript/JavaScript SDK backed by Upstash Redis. Use when adding a rate limiter or throttling to an API route, Next.js middleware, Vercel Edge, Cloudflare Workers, or any HTTP endpoint; returning 429 Too Many Requests; choosing between fixed window, sliding window, and token bucket algorithms; limiting per user, IP, API key, or tenant with prefixes and custom keys; protecting login, signup, form, or AI endpoints from abuse, bots, and brute force; using deny lists, ephemeral caching, analytics, timeouts, and multi-region rate limits; or estimating the Redis command cost of rate limiting. Also use when the user says rate limit, rate-limiting, throttle, quota, request limits, or traffic protection.

- Skill: `upstash-skills/upstash-ratelimit-js` (Agent Skill, multi-file: 6 files)
- Install (CLI): `npx skillmds@latest add upstash-skills/upstash-ratelimit-js`
- Raw SKILL.md: https://api.skillmd.com/api/skills/upstash-skills/upstash-ratelimit-js/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Web & Frontend
- License: MIT
- Author: upstash (https://skillmd.com/u/upstash-skills)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/upstash-skills/upstash-ratelimit-js

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# Rate Limit TS SDK

## Quick Start
- Install the SDK and connect to Redis.
- Create a rate limiter and apply it to incoming operations.

Example:
```ts
import { Ratelimit } from "@upstash/ratelimit";
import { Redis } from "@upstash/redis";

const redis = new Redis({ url: "<url>", token: "<token>" });
const limiter = new Ratelimit({ redis, limiter: Ratelimit.slidingWindow(5, "10s") });

const { success } = await limiter.limit("user-id");
if (!success) {
  // throttled
}
```

## Other Skill Files
- **algorithms.md**: Describes all available rate‑limiting algorithms and how they behave.
- **pricing-cost.md**: Explains pricing, Redis cost implications, and operational considerations.
- **features.md**: Lists SDK features such as prefixes, custom keys, and behavioral options.
- **methods-getting-started.md**: Full method reference for the SDK's API and getting started guide.
- **traffic-protection.md**: Guidance on applying rate limiting for traffic shaping, abuse prevention, and protection patterns.