Common questions about feature flags

Why is my feature flag not working?

Here's a list of suggestions to troubleshoot your flag:

1. Check the feature flags tab on the persons page for your specific person.
   1. If the flag is showing up as disabled here, check the "match evaluation" column to know the reason why.
   2. If the flag is showing up as enabled here, the problem lies somewhere in the implementation (your code).
2. Check if you're calling identify() before the flag is called to get to the right person on your website.
3. Check if an ad-blocker is blocking calls. If yes, you can fix this by deploying a reverse proxy.
4. If none of the above, ask us in the User Slack, we'll help debug.

On my website, why does the feature flag sometimes flicker?

By default, flags are loaded from our servers which takes about 100-500ms. During this time, the flag is disabled, which can be the reason why you see things look differently for the first 500ms.

To fix this, you can bootstrap feature flags.

I care about latency a lot, and 500ms delays are unacceptable on my servers. Can I do something about this?

Yes, use local evaluation. This downloads flag definitions on your servers and evaluates them locally.

My feature flags are sending a lot of events, how can I manage this?

Every library has the option to disable sending these events. Just check the relevant docs for the library for the send_events parameter in your posthog.isFeatureEnabled() or posthog.getFeatureFlag() calls.

However, note that this has a few consequences:

1. The usage tab on the flag will stop showing events since we can't track them anymore.
2. Experiments that depend on trend goals won't work since we use this event to calculate relative exposure. Convert your trend experiments to funnel experiments instead to make this work.