API feature flags installation

Evaluate the feature flag value using flags

Required

flags is the endpoint used to determine if a given flag is enabled for a certain user or not.

curl -v -L --header "Content-Type: application/json" -d '{
    "token": "<ph_project_token>",
    "distinct_id": "distinct_id_of_your_user",
    "groups" : {
        "group_type": "group_id"
    }
}' "https://us.i.posthog.com/flags?v=2"
import requests
import json

url = "https://us.i.posthog.com/flags?v=2"
headers = {
    "Content-Type": "application/json"
}
payload = {
    "token": "<ph_project_token>",
    "distinct_id": "user distinct id",
    "groups": {
        "group_type": "group_id"
    }
}
response = requests.post(url, headers=headers, data=json.dumps(payload))
print(response.json())
const response = await fetch("https://us.i.posthog.com/flags?v=2", {
    method: "POST",
    headers: {
        "Content-Type": "application/json",
    },
    body: JSON.stringify({
        token: "<ph_project_token>",
        distinct_id: "user distinct id",
        groups: {
            group_type: "group_id",
        },
    }),
});
const data = await response.json();
console.log(data);

Note: The groups key is only required for group-based feature flags. If you use it, replace group_type and group_id with the values for your group such as company: "Twitter".

Include feature flag information when capturing events

Required

If you want to use your feature flag to breakdown or filter events in your insights, you'll need to include feature flag information in those events. This ensures that the feature flag value is attributed correctly to the event.

Note: This step is only required for events captured using our server-side SDKs or API.

curl -v -L --header "Content-Type: application/json" -d '{
    "token": "<ph_project_token>",
    "event": "your_event_name",
    "distinct_id": "distinct_id_of_your_user",
    "properties": {
        "$feature/feature-flag-key": "variant-key"
    }
}' https://us.i.posthog.com/i/v0/e/
import requests
import json

url = "https://us.i.posthog.com/i/v0/e/"
headers = {
    "Content-Type": "application/json"
}
payload = {
    "token": "<ph_project_token>",
    "event": "your_event_name",
    "distinct_id": "distinct_id_of_your_user",
    "properties": {
        "$feature/feature-flag-key": "variant-key"
    }
}
response = requests.post(url, headers=headers, data=json.dumps(payload))
print(response)

Send a $feature_flag_called event

Optional

To track usage of your feature flag and view related analytics in PostHog, submit the $feature_flag_called event whenever you check a feature flag value in your code.

You need to include two properties with this event:

$feature_flag_response: This is the name of the variant the user has been assigned to e.g., "control" or "test"
$feature_flag: This is the key of the feature flag in your experiment.

curl -v -L --header "Content-Type: application/json" -d '{
    "token": "<ph_project_token>",
    "event": "$feature_flag_called",
    "distinct_id": "distinct_id_of_your_user",
    "properties": {
        "$feature_flag": "feature-flag-key",
        "$feature_flag_response": "variant-name"
    }
}' https://us.i.posthog.com/i/v0/e/
import requests
import json

url = "https://us.i.posthog.com/i/v0/e/"
headers = {
    "Content-Type": "application/json"
}
payload = {
    "token": "<ph_project_token>",
    "event": "$feature_flag_called",
    "distinct_id": "distinct_id_of_your_user",
    "properties": {
        "$feature_flag": "feature-flag-key",
        "$feature_flag_response": "variant-name"
    }
}
response = requests.post(url, headers=headers, data=json.dumps(payload))
print(response)

4
Running experiments
Optional
Experiments run on top of our feature flags. Once you've implemented the flag in your code, you run an experiment by creating a new experiment in the PostHog dashboard.

Next steps

Recommended

Now that you're evaluating flags, continue with the resources below to learn what else Feature Flags enables within the PostHog platform.

Resource	Description
Creating a feature flag	How to create a feature flag in PostHog
Adding feature flag code	How to check flags in your code for all platforms
Framework-specific guides	Setup guides for React Native, Next.js, Flutter, and other frameworks
How to do a phased rollout	Gradually roll out features to minimize risk
More tutorials	Other real-world examples and use cases

API feature flags installation

Evaluate the feature flag value using flags

Include feature flag information when capturing events

Send a $feature_flag_called event

Running experiments

Next steps

Community questions

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