Configure Cloudflare Rate Limiting to protect your website application against denial-of-service attacks, brute-force login attempts, and other abusive behaviors.

Overview

Cloudflare Rate Limiting automatically identifies and mitigates excessive request rates for specific URLs or for an entire domain.  Request rates are calculated locally for individual Cloudflare data centers.  The most common uses for Rate Limiting are DDoS protection, Brute-force attack protection, and to limit access to forum searches, API calls, or resources that involve database-intensive operations at your origin. 

Once an individual IPv4 address or IPv6 /64 IP range exceeds a rule threshold, further requests to the origin web server are blocked with an HTTP 429 response that includes a Retry-After header to indicate when the client can resume sending requests.

Analytics

View Rate Limiting analytics in the Cloudflare Analytics app under the Security tab. Rate Limiting analytics uses solid lines to represent traffic that matches simulated requests and dotted lines to portray actual blocked requests. Logs generated by a Rate Limiting rule are only visible to Enterprise customers via Cloudflare Logs. 

Cloudflare returns an HTTP 429 error for blocked requests.  Details on blocked requests per location are provided to Enterprise customers under Status Codes analytics in the Cloudflare Analytics app under the Traffic tab. 

Rate Limiting allowances per plan

The number of allowed Rate Limiting rules depends on the domain’s plan:

Cloudflare Rate Limiting supports multiple levels of configuration control depending on the domain’s Cloudflare plan.  The table below maps out what you can do based on your plan:

Components of a Rate Limiting rule

A Rate Limiting rule consists of three distinct components.  Click a component below to expand the details:

Identify rate-limit thresholds

To identify a general threshold for Cloudflare Rate Limiting, divide 24 hours of uncached website requests by the unique visitors for the same 24 hours. Then, divide by the estimated average minutes of a visit.  Finally, multiply by 4 (or larger) to establish an estimated threshold per minute for your website. A value higher than 4 is fine since most attacks are an order of magnitude above typical traffic rates.

To identify URL rate limits for specific URLs, use 24 hours of uncached requests and unique visitors for the specific URL.  Adjust thresholds based on user reports and your own monitoring.

Task 1: Configure a basic Rate Limiting rule

Click to expand details on creating the two common types of Cloudflare Rate Limiting rule.

To create a custom rule:

1. Log in to the Cloudflare dashboard.

2. Select the appropriate domain.

3. Click the Firewall app and select the Tools tab.

4. Click Create a custom rule.  A dialog opens where you specify the details of your new rule.

5. Enter a descriptive Rule Name.

6. For If Traffic Matching the URL, select an HTTP scheme from the dropdown as well as a URL.

7. In from the same IP address exceeds, enter an integer greater than 1 to represent the  number of requests in a sampling period.

8. For requests per, select the sampling period (the period during which requests are counted). Domains on Enterprise plans can enter manually any duration between 10 seconds and 3600 seconds (1 hour).

9. For the Then dropdown, pick one of the available actions based on your plan.  Review the Rule Mitigation section of Components of a Rate Limiting Rule above for details.

10. If you selected Block or Log, for matching traffic from that visitor for, select how long to apply the option once a threshold has been triggered. Domains on Enterprise plans can enter any value between 10 seconds and 86400 seconds (24 hours).

11. To activate your new rule, click Save and Deploy.

12. The Rule Name appears in your Rate Limiting rules list.

In general, when setting a lower threshold:

1. Leave existing rules in place and add a new rule with the lower threshold.
2. Once the new rule is in place, wait for the action duration of the old rule to pass before deleting the old rule.

When setting a higher threshold (due to legitimate client blocking), increase the threshold within the existing rule.

Task 2: Configure Advanced Criteria (only Business and Enterprise plans)

The Advanced Criteria option configures which HTTP methods, header responses, and origin response codes to match for your Rate Limiting rule.

To configure your advanced criteria for a new or existing rule, follow these steps:

1. Click Advanced Criteria.

2. Select a value from the Method(s) dropdown.  ANY is a default that matches all HTTP methods.

3. Filter by HTTP Response Header(s). The CF-Cache-Status header appears by default so that Cloudflare serves cached resources rather than rate limit those resources.  Click Add header response field to include headers returned by your origin web server.

If you have more than one header under HTTP Response Header(s), an AND boolean logic applies.  To exclude a header, use the Not Equals option. Also, each header is case insensitive.

4. Under Origin Response code(s), enter the numerical value of each HTTP response code to match.  Separate two or more HTTP codes with a comma; for example: 401, 403 

5.  Click Save and Deploy or configure additional Rate Limiting features allowed for your plan.

Task 3: Configure Advanced Response (only Business and Enterprise plans)

The Advanced Response option configures the information format returned by Cloudflare when a rule's threshold is exceeded and is configured via the following steps:

1. Click Advanced Response.

2. Select a Response type format. The maximum response size is 32kb.

To display a custom HTML page or more than the 32kB limit, add a meta refresh to the Rate Limiting rule via the Cloudflare API via the Response object of the Action parameter.  For example: 

"response": { "content_type": "text/html", "body": "\u003cmeta http-equiv=\"refresh\" content=\"0; url=https://www.example.com/about\" /\u003e"}

Your Rate Limiting rule must not match the redirect URL.  To protect from DDoS, the page for the redirect must include resources cached by Cloudflare.

3. Click Save and Deploy or configure additional features based on your plan.

Task 4: Configure the Bypass option (Enterprise plans only)

Bypass creates an allowlist or exception so that no actions apply to a specific set of URLs even if the rate limit is matched.  Configure a Bypass via the following steps:

1. Click Bypass. 

2. In the Bypass rule for these URLs text box, enter the URL(s) to exempt from the rate limiting rule. Enter each URL on its own line. An HTTP or HTTPS specified in the URL is automatically removed when the rule is saved and instead applies to both HTTP and HTTPS.

3. Click Save and Deploy, or configure additional features based on your plan.

Order of rule execution

Use case 1: If a request matches with both rules below,

• rule 1: matching with test.example.com
• rule 2: matching with *.example.com*

or

• rule 1: matching with *.example.com*
• rule 2: matching with test.example.com

then rule 2 will always trigger first because it was created last.

Use case 2: By removing the asterisk (*) at the end of the domain, rule execution will depend on which rule was created the last.

• rule 1: matching with test.example.com
• rule 2: matching with *.example.com

rule 2 above triggers first if a request matches both rules.

• rule 1: matching with *.example.com
• rule 2: matching with test.example.com

rule 2 above triggers first if a request matches both rules.

Related resources

• Billing for Cloudflare Rate Limiting
• How is Rate Limiting reported in ELS (Enterprise Log Share)?
• Troubleshooting Cloudflare Rate Limiting
• Configure Rate Limiting via the Cloudflare API