Segments allow you to group your users based on a set of rules, and then control Feature Flags and Remote Config for those groups. You can create a Segment and then override a Feature Flag state or Remote Config value for that segment of users.
Segments for Flags and Config are overridden at the Environment level, meaning that different Environments can define their own Segment overrides.
Segments only come into effect if you are getting the Flags for a particular Identity. If you are just retrieving the flags for an Environment without passing in an Identity, your user will never be applied to a Segment as there is no context to use.
Segments are not sent back to client SDKs. They are used to override flag values within the dashboard, but they are never sent back to our SDKs from the API. Learn more about our architecture.
Example - Beta Users
Segment definitions can be defined at the Project or Flag level. Project level Segments are defined at the Project level and can be used with any number of Flags within that Project. Flag Specific Segments can only affect the Flag they are defined within.
You can create a new Segment by going navigating to Segments and clicking the "Create Segment" button, call it
Beta Users, and define a single rule:
Once the Segment has been defined, you can then associate that Segment with a specific Feature Flag. To do this, open the Feature Flag that you want to connect the Segment to and navigate to the Segment Overrides tab. You then have the option of connecting a Segment to the Feature. This then allows you to override the flag value for Users that are within that Segment. If the Identified user is a member of that Segment, the flag will be overridden.
For all the Feature Flags that relate to Beta features, you can associate this
Beta Users segment with each Flag, and
set the Flag value to
true for that Segment. To do this, edit the Feature Flag and select the segment in the 'Segment
Overrides' drop down.
At this point, all users who log in with an email address that contains
@flagsmith.com will have all Beta features
Let's say that you then partner with another company who need access to all Beta features. You can then modify the Segment rules:
Now all users who log in with a
@solidstategroup.com email address are automatically included in beta features.
You can also create Segments within a Feature. This means that only that Feature can make use of that Segment. Feature Specific Segments are useful when you know you will only need to use that Segment definition once. Go to the Feature, then the Segment Overrides Tab, and click the "Create Feature-Specific Segment" button.
If you are using Multi-Variate Flag Values, you can also override the individual value weightings as part of a Segment override.
Some of the operators in local evaluation mode are only supported in later SDK versions, see SDK Compatibility.
The full set of Flagsmith rule operators are as follows:
|Trait value is equal to segment value.|
|Trait value is not equal to segment value.|
|Identity is in the percentage bucket. See Percentage Split Operator.|
|Trait value is greater than segment value.|
|Trait value is greater than or equal to segment value.|
|Trait value is less than segment value.|
|Trait value is less than or equal to segment value.|
|Trait value is equal to one or more elements in a comma delimited list. See The |
|Segment value is a substring of trait value.|
|Segment value is not a substring of the trait value.|
|Segment value, set to a valid Regex expression, is applied to trait value and matches it.|
|Trait value is set for given identity and trait key.|
|Trait value is not set for given identity and trait key.|
|Trait value is set to a newer SemVer-formatted version than segment value. See SemVer-aware operators.|
|Trait value is set a newer SemVer-formatted version than segment value or equal to it. See SemVer-aware operators.|
|Trait value is set to an older SemVer-formatted version than segment value. See SemVer-aware operators.|
|Trait value is set to an older SemVer-formatted version than segment value or equal to it. See SemVer-aware operators.|
Some of the operators also have special powers, described below.
In operator lets you match a Trait value against a comma-separated list of values. For example, the Segment rule
value might read
21,682,8345. This would then match against a Trait value of
682 but not against a Trait value of
In operator can be useful when building Segments to match against tenancies within your application. Let's say you
wanted a Segment to evaluate as true for 5 different customer tenancies. Create a Segment rule where the
matches all of those 5 customer tenancy ID's and no others. You can then create a Trait value for the Identity that
contains the tenancy ID of that user.
In operator is case sensitive when evaluating alphabetical characters.
The following SemVer operators are also available:
For example, if you are using the SemVer system to version your application, you can store the version as a
Flagsmith and then create a rule that looks like, for example:
This Segment rule will include all users running version
4.2.52 or greater of your application.
When you store Trait values against an Identity, they are stored in our API with an associated type:
When you define a Segment rule, the value is stored as a String. When the Segment engine runs, the rule value will be coerced into the type of the Trait value. Here are some examples.
So here you are storing a native
boolean value against the Identity. You can then define a Segment rule, e.g.
accepted_cookies=true. Because the Identity trait named
accepted_cookies is a boolean, the Segment engine will
coerce the string value from
accepted_cookies=true into a boolean, and things will work as expected.
If you were to then change the trait value to a String at a later point the Segment engine will continue to work, because the Identity's Trait value has been stored as a String
For evaluating booleans, we evaluate the following 'truthy' String values as
Percentage Split Operator
The percentage split operator only comes into effect if you are getting the Flags for a particular Identity. If you are just retrieving the flags for an Environment without passing in an Identity, your user will never be included in the percentage split segment.
When you use a percentage split operator in a segment that is overriding a feature, each user will be placed into the same 'bucket' whenever that feature is evaluated for that user, and hence they will always receive the same value. Different users will receive different values depending on your split percentage.
This operator performs modulo operation. This operator accepts rule
divisor|remainder format and is applicable for Traits having
float values. For example:
This segment rule will include all identities having
userId trait and having a remainder equal to 0
after being divided by 2.
userId % 2 == 0
Segment Rule Ordering
Flagsmith evaluates the conditions of a Segment in the order they are defined. This can affect how things are processed and should be considered when creating your Segment rules.
For example, let’s say I have this segment:
- Percentage Split = 10%
- isSubscriber = true
This Segment would randomly select 10% of all Identities first and then filter the subscribers. You could also define the Segment rules the other way around:
- isSubscriber = true
- Percentage Split = 10%
This definition makes the isSubscriber check first, and the Split condition is second, operating purely on the pool of subscribed users.
Feature Flag and Remote Config Precedence
Feature Flag states and Remote Config values can be defined in 3 different places:
- The default Flag/Config value itself
- The Segment associated with the Flag/Config
- Overridden at an Identity level
For example, a Feature Flag
Show Paypal Checkout could be set to
false on the Flag itself,
true in the Beta Users
segment, and then overridden as
false for a specific Identity.
In order to deal with this situation, there is an order of priority:
- If the Identity has an override value, this is returned ahead of Segments and Flags/Config
- If there's no Identity override, the Segment is checked and returned if valid
- If no Identity or Segment overrides the value, the default Flag/Config value is used
More simply, the order of precedence is: