PostHog vs Google Analytics 4 for Conversion Tracking
For conversion tracking, PostHog and GA4 solve overlapping but different problems. PostHog is built for product analytics — event-level data, easy funnels, session replay, and feature flags — which suits diagnosing why people don't convert. GA4 is free, everywhere, and strong on marketing acquisition, but its aggregated model and funnel UX make product-level conversion analysis harder.
For conversion tracking, PostHog and GA4 overlap but solve different problems. PostHog is built for product analytics — event-level data, easy funnels, session replay — which suits diagnosing why people don't convert. GA4 is free, ubiquitous, and strong on marketing acquisition, but its aggregated model makes product-level conversion analysis harder. Plenty of teams run both.
What each is actually for
- PostHog is a product-analytics platform. It stores individual events you can query directly (HogQL), build funnels from in a few clicks, replay sessions to watch real drop-off, and attach feature flags for experiments. Its centre of gravity is what happens inside your product.
- GA4 is a web/marketing analytics platform. Its strength is acquisition: where traffic comes from, channel attribution, and tight Google Ads integration. Its centre of gravity is how people arrive.
For conversion work specifically — finding the funnel step that leaks and seeing the behaviour behind it — PostHog's event-first design fits more naturally.
The honest comparison
| Dimension | PostHog | GA4 |
|---|---|---|
| Price | Generous free tier, then usage-based | Free (GA4 standard) |
| Data model | Event-level, queryable | Aggregated reports, some sampling/thresholding |
| Funnels | Purpose-built, granular | Possible via Explorations, less direct |
| Session replay | Built in | Not native |
| Feature flags / experiments | Built in | Not native (Optimize was retired) |
| Acquisition & ad attribution | Basic | Excellent, Google Ads native |
| Setup effort | Snippet + some modelling | Snippet, ubiquitous tooling |
| Privacy posture | Self-host option, EU hosting | Google-hosted; consent/region concerns for some |
Where GA4 wins
GA4 isn't the weaker tool — it's a different tool. It wins when:
- You need channel attribution and to tie conversions back to ad spend.
- You want a free, universally-supported standard every marketer already knows.
- Your main question is acquisition, not in-product behaviour.
Dismissing GA4 as "just marketing analytics" understates how good it is at that job.
Where PostHog wins
PostHog wins when the question moves from acquisition to behaviour:
- Funnel diagnosis — which step loses the most people, segmented by anything.
- Session replay — watching a real visitor stall on the form you suspect.
- Event-level queries — computing a metric exactly the way you define it.
- Experiments — feature flags and A/B testing in the same tool.
For the kind of conversion work that ends in a code change, that depth matters.
The pragmatic answer: often both
These tools aren't mutually exclusive, and treating the choice as either/or is a false dilemma. A common, sensible setup:
- GA4 owns acquisition and ad attribution.
- PostHog owns product behaviour, funnels, and conversion diagnosis.
Be clear about which tool answers which question, and you avoid the trap of trying to force one to do the other's job.
From measurement to change
Whichever you use for conversion, the analysis is only worth anything if it leads to a fix. PostHog's event-level funnels make it straightforward to find the leak; the next step is shipping the change. If you'd like that change found from your PostHog data and opened as a Pull Request each week, that's what Velyr does.
Frequently asked questions
Is PostHog or GA4 better for conversion tracking?
It depends on the question. For product-level conversion — why people drop off in your funnel — PostHog's event-level data, funnel builder, and session replay are stronger. For marketing acquisition and channel attribution, GA4 is free, ubiquitous, and integrated with Google Ads. Many teams run both.
Can I use both PostHog and GA4?
Yes, and many teams do. GA4 handles acquisition and ad attribution; PostHog handles product behaviour and funnel diagnosis. They answer different questions, so running both is common rather than redundant — just be clear which tool owns which decision.
Why is GA4 harder for funnel analysis?
GA4's model leans on aggregated reports and applies thresholding and sometimes sampling, and its exploration funnels are less direct than a purpose-built product-analytics funnel. You can do funnel analysis in GA4, but it's more work and less granular than in a tool designed event-first.
Velyr is an AI growth agent that ships one weekly conversion fix as a GitHub Pull Request — you approve it over Telegram, and it rolls itself back if the numbers drop.
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