# Source: https://gofastmcp.com/python-sdk/fastmcp-server-middleware-rate_limiting.md

> ## Documentation Index
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> Use this file to discover all available pages before exploring further.

# rate_limiting

# `fastmcp.server.middleware.rate_limiting`

Rate limiting middleware for protecting FastMCP servers from abuse.

## Classes

### `RateLimitError` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L15" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Error raised when rate limit is exceeded.

### `TokenBucketRateLimiter` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L22" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Token bucket implementation for rate limiting.

**Methods:**

#### `consume` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L38" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python  theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
consume(self, tokens: int = 1) -> bool
```

Try to consume tokens from the bucket.

**Args:**

* `tokens`: Number of tokens to consume

**Returns:**

* True if tokens were available and consumed, False otherwise

### `SlidingWindowRateLimiter` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L61" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Sliding window rate limiter implementation.

**Methods:**

#### `is_allowed` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L76" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python  theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
is_allowed(self) -> bool
```

Check if a request is allowed.

### `RateLimitingMiddleware` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L92" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Middleware that implements rate limiting to prevent server abuse.

Uses a token bucket algorithm by default, allowing for burst traffic
while maintaining a sustainable long-term rate.

**Methods:**

#### `on_request` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L152" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python  theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
on_request(self, context: MiddlewareContext, call_next: CallNext) -> Any
```

Apply rate limiting to requests.

### `SlidingWindowRateLimitingMiddleware` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L170" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

Middleware that implements sliding window rate limiting.

Uses a sliding window approach which provides more precise rate limiting
but uses more memory to track individual request timestamps.

**Methods:**

#### `on_request` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L219" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python  theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
on_request(self, context: MiddlewareContext, call_next: CallNext) -> Any
```

Apply sliding window rate limiting to requests.