Rules are used to enable a flag for a subset of users. Rules are evaluated from top to bottom. If a rule matches, the flag will return the configured value and stop evaluating the remaining rules. See the example below. Each rule has an attribute (1), a comparison operator (2), one or multiple targets (3) and an output value (4). Rule

​
Available Attributes

​
Geolocation Attributes

Geolocation is not available when running your edge function locally in development.

​
City

The city name for the location of the requester’s public IP address. Non-ASCII characters are encoded according to RFC3986.

​
Country

Countries are identified by their ISO 3166-1 alpha-2 code. We provide a list of many available countries as suggestions in the input component in the console. Countries

​
IP

The public IP address of the client that made the request.

​
Region

A string of up to three characters containing the region-portion of the ISO 3166-2 code for the first level region associated with the requester’s public IP address. Unfortunately, there is no official extensive list of available regions from Vercel.

​
Custom Attribute

You can use custom attributes to enable a flag for a subset of users. For example, you can enable a flag for users with a specific userId or email. Please refer to the API documentation for more information on how to set custom attributes.

​
Comparison Operators

These are the available rule types. Each of them includes a small code snippet that shows the exact implementation for reference value is the value of the attribute. target is what we compare the attribute value to.

​
is in array

The rule will apply if the attribute is in the target array. 
return target.includes(attribute);

​
is not in array

The rule will apply if the attribute is not in the target array. 
return !target.includes(attribute);

​
contains

The rule will apply if the attribute contains the specified target. 
return attribute.includes(target);

​
does not contain

The rule will apply if the attribute value does not contain the specified target. 
return !attribute.includes(target);

​
equals

The rule will apply if the attribute value equals the specified targe. 
return attribute === target;

​
does not equal

The rule will apply if the attribute value does not equal the specified target. 
return attribute !== target;

​
is empty

The rule will apply if the attribute value is empty. 
return attribute === "";

​
is not empty

The rule will apply if the attribute value is not empty. 
return attribute !== "";

​
is greater than

The rule will apply if the attribute value is greater than the specified value. 
return attribute > target;

​
is greater than or equals

The rule will apply if the attribute value is greater than or equals the specified value. 
return attribute >= target;

​
is less than

The rule will apply if the attribute value is less than the specified value. 
return attribute < target;

​
is less than or equals

The rule will apply if the attribute value is less than or equals the specified value. 
return attribute <= target;

​
Example

The following flag will be evaluated for 80% of all users and enabled for those in Germany or the United Kingdom and for users with the attribute userId set to chronark. Flag

​
First Rule matches

Let’s assume our user is lucky enough to be chosen for the 80% and is located in Germany: The order of operations is as follows:
  1. Evaluate percentage: ✅
  2. Evaluate country: ✅ Since the user is located in Germany, and that is one of the countries specified in the rule, the value true will be returned.

​
Any Rule matches

Our user is located in Norway and their userId is chronark, the order of operations is as follows:
  1. Evaluate country: ❌
  2. Evaluate userId: ✅
All rules will be avaluated until one of them matches. In this case, the flag will return true.

​
Percentage fall through

Our user is not lucky enough to be chosen for the 80%: In this case the rules will not be avalated and the flag returns false

​
No rule hit

Lastly, let’s look at what happens if none of the rules match: If your user is in the United States, and their username is not chronark:
  1. Evaluate country: ❌
  2. Evaluate userId: ❌
The flag will return false.