PostHog feature flags vs LaunchFlag: when you need analytics and when you need a switch

Both products give you a boolean you can flip without a deploy. The difference is everything attached to that boolean.

PostHog feature flags are one surface on a product analytics platform. The flag sits next to your events, your session replays and your experiments, and that is the point: you roll a feature out to 5 percent and then look at what those 5 percent did. Flags and experiments are billed on the same request meter.

LaunchFlag is one surface. A switch, three environments, an audit log, and nothing else. No event pipeline, no funnel, no metric attached to a flag, and none of that is coming. It is $12 a month flat, and the fastest thing it does is turn something off.

So the question is not which product is better. It is which job you are hiring for. If the job is "which variant won", that is PostHog. If the job is "the checkout is broken and I am on a train", that is LaunchFlag.

Start with what PostHog actually ships, because it is a lot more than a boolean.

Four flag types. When you create a flag, PostHog offers boolean, multivariate, remote config and experiment. Boolean flags return "false if the flag is disabled, true if the flag is enabled and has a matching release condition, and null or undefined if no release condition matches". Multivariate flags "return a key, for example control or test", and users are bucketed by the rollout percentages you set.

Targeting that knows your users. Release conditions take a rollout percentage with precision down to 0.01 percent, plus person properties, cohorts and groups. That last part is the real advantage and it is easy to undersell. PostHog already knows which users are on the Pro plan, signed up in March and fired checkout_started twice, so you can target that cohort without assembling it yourself. A standalone flag service cannot do that, because it knows nothing about your users except what you hand it at evaluation time.

Local evaluation on the server. The Node, Ruby, Go, Python, C# / .NET, PHP, Java, Rust and Elixir SDKs can decide flags in your process: "Instead of making a request for each flag, PostHog will periodically request and store feature flag definitions locally." Definitions refresh every 30 seconds, or every 5 minutes in the Go SDK. It needs a separate secure API key, and you have to pass in the person properties yourself, since your server holds them and PostHog is not in that loop. It does not work with experience continuity, early access links, static cohorts or is_not_set operators.

The measurement loop. This is the actual reason to use PostHog flags. The flag is wired to session replays, events and exceptions, and experiments are billed with flags, so "did the rollout work" is answered in the same tool that served the flag, with the statistics done for you. I am not building that and would not try. If you already run PostHog, its flags cost you one dashboard visit of setup and give you a measurement loop nobody standalone can match.

LaunchFlag exists for one job: making a shipped feature reversible in seconds, by one person, from a phone, with no deploy involved.

That job has four requirements and none of them are analytics.

• The old path still runs. A kill switch is a design decision you make before you ship, not a setting you turn on afterwards. If you deleted oldCheckout the day you shipped newCheckout, no flag service saves you.
• Off is the safe side. Every flag carries a fail mode. Closed for money, auth and deletion. Open for cosmetics, where a nav bar vanishing because a config fetch timed out is worse than the new nav.
• You can reach it from a phone. The dashboard is mobile first because incidents do not wait for you to be at a desk.
• Every flip leaves a record. Who, what, when, which environment, in an audit log, with roles (owner, developer, viewer) deciding who can flip what.

Around that sit the things the job needs and nothing more. Boolean and multivariate flags. Three environments (dev, staging, prod) with one-tap promotion. Targeting by everyone, logged-in, percentage, first N users or an allowlist. One Emergency off that kills every flag in a project at once. Flags register themselves the first time your code evaluates them, off everywhere, so you never have to create a flag before writing the branch that reads it.

The other half is agents. More of what goes to production now was not typed by the person who approved it. LaunchFlag ships an agent skill and a hosted MCP server, so Claude Code or Cursor can wrap a risky change in a flag and register it without you. A flag around code you read but did not write is the cheapest insurance in the business.

Two rows deserve a note rather than a cell. On pricing, a PostHog frontend request fires when the SDK initialises, when a user is identified, when user properties update, when you call reloadFeatureFlags, and when you create a group. That is a usage shape worth modelling before you assume 1M is generous or stingy for your traffic. And on the audit and agent rows, "not covered by the pages cited below" means exactly that: I checked the pages listed at the end and did not find it, not that the feature is missing.

Pick PostHog if any of these is true.

• You already run PostHog. The marginal cost of using its flags is close to zero and the measurement is free. Adding a second vendor to flip booleans is a worse trade than it looks.
• You are running experiments, not rollouts. If the sentence you want to say is "variant B lifted conversion 4 percent with p under 0.05", you need the analytics attached to the assignment. Nothing I ship gives you that.
• Your targeting depends on behaviour. Cohorts built from events, person properties set months ago, group analytics for B2B accounts. That data lives in PostHog, and targeting is much cheaper where the data already is.
• You want early access programmes and remote config in the same place as the flag.

There is no clever counter-argument to any of those. If that is your situation, use their flags.

Pick LaunchFlag if any of these is true.

• The flag is a kill switch, not an experiment. You are not going to analyse it. You are going to turn it off at 19:12 on a Tuesday.
• You do not run product analytics and do not want to start. Installing an analytics platform to get a boolean is a large amount of surface area for a small amount of switch, and it comes with a cookie banner conversation you did not ask for.
• You want a flat bill. $12 or $29 a month, no seats, no per-request meter to model. See pricing.
• A coding agent writes some of your code. The skill and the MCP server mean the agent wraps its own risky change in a flag.
• You want the flag to be boring. Three environments, an audit log, fail modes, an emergency off, and nothing else to learn.

The two-tool answer is not a compromise, it is what I actually do.

PostHog measures. LaunchFlag switches. The flag key is the same string in both places if you want it to be, and the events you send PostHog can carry which arm a user saw, so the analysis still works.

The reason to split them is that they want different things from you. A tool that owns your experiment analytics has a quiet interest in your flags living forever, because a flag with history attached is a flag with value attached. A tool that only owns the switch wants you to delete flags, because the good end state for any flag is that it stops existing. That is why the only number LaunchFlag keeps is evaluations per day: it is what surfaces the flags nobody has touched in 30 days that production is still asking about.

To be explicit about the trade, since this is a comparison post and you should know what you are giving up: LaunchFlag deliberately has no funnels. No session replay, no significance test, no metric attached to a flag. If you run a multivariate flag, it serves the arm and records nothing else about it. That is a real limitation and it is on purpose, not on the roadmap.

The whole LaunchFlag integration is one import and one if. There is no flag to create first, no YAML, no dashboard step.

import { flag } from "launchflag";

if (await flag("checkout_v2", user.id)) return newCheckout(cart);
return oldCheckout(cart);

For comparison, the PostHog web equivalent is an install, an init with your project token, and the check.

import posthog from "posthog-js";

posthog.init("<ph_project_token>", { api_host: "https://us.i.posthog.com", defaults: "2026-05-30" });
if (posthog.isFeatureEnabled("checkout_v2")) { /* ... */ }

Neither is hard. The difference is what the second line pulls in: PostHog gives you a client that also captures, identifies and replays, which is exactly what you want if you are there for the analytics and exactly what you are paying for if you are not.

One command sets LaunchFlag up, writing the dev key into .env.local, downloading the agent skill and configuring the MCP server.

$ npx launchflag init

The rest, variants, environments, the raw API and what happens when we are unreachable, is in the docs.

All checked on 4 September 2026. PostHog moves fast, so verify prices and limits at the source before you make a decision on them. Where a number was not on the page I read, this post says so rather than guessing.

• Feature flags product page: https://posthog.com/feature-flags
• Creating feature flags, flag types and release conditions: https://posthog.com/docs/feature-flags/creating-feature-flags
• Local evaluation, polling intervals and limitations: https://posthog.com/docs/feature-flags/local-evaluation
• Bootstrapping and behaviour on an errored response: https://posthog.com/docs/feature-flags/bootstrapping
• Web installation snippet: https://posthog.com/docs/feature-flags/installation/web
• What counts as a feature flag request: https://posthog.com/docs/billing/estimating-usage-costs
• Projects per environment: https://posthog.com/docs/data/environments
• Pricing and the free request allowance: https://posthog.com/pricing