This post contains affiliate links to PostHog, Plausible, and Fathom. I run PostHog in production for product analytics on a SaaS funnel. I evaluated Plausible and Fathom when I wanted lightweight, privacy-first traffic numbers for a couple of marketing sites.
I run PostHog in production to instrument a SaaS signup→activation funnel. I evaluated Plausible and Fathom when all I wanted was clean traffic numbers for a few static marketing sites. People treat these three as competitors. They're not — they answer different questions. Pick the wrong one and you either drown in a product-analytics suite you don't need, or you outgrow a pageview counter in a month.
Short version
You want to answer product questions — "where in the funnel do users drop, which feature drives retention, what does this cohort do" — and you're willing to instrument events: PostHog.
You want traffic questions answered — "how many people hit this page, where did they come from" — with a privacy-first script, no cookie banner, and a dashboard your marketing person can read: Plausible or Fathom.
Between the two simple ones: Plausible if you lean open-source / self-host-optional and want goals + funnels included; Fathom if you want the most polished hosted product and best-in-class uptime with zero ops.
What PostHog actually is (and why it's a different category)
PostHog is a product-analytics platform, not a traffic counter. The unit isn't a pageview — it's an event you define and capture (signup_completed, trace_created, checkout_started). On top of that event stream you get:
- Funnels — define an ordered set of events and see conversion + drop-off between each step. This is the whole reason I run it: I can see exactly how many users go signup → email-verified → first-action → checkout, and where they fall out.
- Session replay — watch real (anonymized) sessions to see why a step drops.
- Feature flags + experiments — ship behind a flag, ramp it, A/B test, all in the same tool that measures the result.
- Cohorts + retention — "users who did X in week 1, did they come back in week 4."
- Self-host or cloud — open-source core; run it yourself or use PostHog Cloud.
The cost of all that power is instrumentation. PostHog only knows what you tell it to capture. You add a client or server SDK, fire events at the meaningful moments, and design your funnels. That's real work. If you just want "how many people visited the blog," PostHog is wildly over-spec'd and you'll resent the setup.
One real gotcha I hit: server-side captured events lose client context. If you fire events from your backend (e.g. a Cloudflare Worker), the $referrer and $ip PostHog sees are your edge's, not the visitor's — so attribution and "is this real vs test traffic" get muddy unless you also capture client-side or tag events with a source/is_test property. Plan your event schema before you wire it, not after.
Where Plausible wins
Privacy-first by design. No cookies, no persistent identifiers, GDPR/CCPA/PECR-friendly out of the box. No cookie-consent banner needed. The script is ~1KB.
Open source + self-host option. Plausible is fully open-source. Run their hosted version, or self-host on your own box if data residency matters to you or your client.
Goals and funnels included. You don't get product-analytics depth, but you do get conversion goals and basic funnels — more than a pure pageview counter, without the PostHog learning curve.
One clean dashboard. A single page anyone can read: top pages, top sources, countries, devices. No training required. Hand it to a non-technical co-founder and they get it immediately.
Fair pricing on pageviews. Priced by monthly pageviews, and the lower tiers are genuinely cheap for a marketing site.
Where Fathom wins
The most polished hosted experience. Fathom is laser-focused on being the best simple, privacy-first analytics product — and it shows. Fast dashboard, clean UX, sensible defaults.
Bypasses ad-blockers better. Fathom puts real effort into first-party/proxied script delivery so you lose fewer measurements to ad-blockers than a naively-installed third-party script.
Uptime + zero ops. Fully managed, strong reliability track record. You will never think about it. No self-host temptation, no maintenance.
Email reports + uptime monitoring. Scheduled email digests and built-in uptime monitoring are nice touches for solo founders who don't want to live in a dashboard.
Privacy as a first-class promise. Like Plausible: no cookies, no consent banner, GDPR-friendly. Marketed hard on privacy, and it holds up.
Where PostHog wins
It answers product questions, period. Funnels, retention, replays, flags, experiments — Plausible and Fathom simply don't do this. If your question is "why do users churn after onboarding," only PostHog (in this trio) can tell you.
Generous free tier. PostHog Cloud has a large monthly free event allowance, which covers most early-stage products before you pay anything. For a pre-revenue SaaS validating a funnel, this matters.
One tool instead of four. Analytics + session replay + feature flags + experiments + a CDP-lite in one platform. Stitching Plausible + LaunchDarkly + a replay tool together costs more and integrates worse.
Server-side + client-side capture. You can instrument a backend-heavy app (workers, queues, webhooks) where there's no browser at all — something a script-tag-only tool can't do.
The cost reality
Plausible: priced by monthly pageviews; entry tiers are inexpensive for a typical marketing site, and self-hosting is free-as-in-infrastructure if you want it.
Fathom: flat-ish hosted pricing by pageviews across unlimited sites on a plan — attractive if you run several marketing sites under one account.
PostHog: usage-based per event/recording with a large free monthly allowance. Cheap-to-free while you're small; you start paying as event volume grows, and a chatty event schema can run up the bill — so capture meaningful events, not everything.
The decision tree I actually use
Static marketing site, blog, landing page — I just need traffic + sources: Plausible or Fathom.
Several marketing sites I want under one clean account: Fathom.
I want open-source / the option to self-host the simple analytics: Plausible.
A SaaS product where I need to measure a signup→activation→paid funnel: PostHog.
I need feature flags / A/B tests measured against the same event stream: PostHog.
A backend-heavy app with events firing server-side: PostHog (the only one of the three that fits).
What I actually do
I run PostHog on the SaaS funnel because I need to see exactly where users drop between signup and activation — no pageview counter answers that. I reach for Plausible or Fathom on the plain marketing sites, where a privacy-first script and a one-page dashboard are the entire requirement and PostHog would be overkill. The mistake isn't picking the "wrong" tool — it's using one tool for both jobs. They're not substitutes.
Links
- PostHog — product analytics, funnels, replay, flags; what I run on the SaaS funnel
- Plausible — privacy-first, open-source, self-host option
- Fathom — the most polished hosted privacy-first analytics
More production-use tool comparisons like this one at tools.thesoundmethod.me, written from real use, not vendor PR.
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