GTM Analytics

For your stack

SaaS product analytics tools

Product analytics answers different questions from web analytics, costs more in every sense, and is regularly bought for the wrong half of the site.

Original abstract illustration in the form of a scatter plot, drawn for this guide

The most expensive mistake in this market is installing a product analytics platform to measure a marketing site. It happens constantly, it produces a heavy page, a consent banner and an event taxonomy nobody maintains, and the reports it unlocks answer questions a marketing site does not have.

The reverse mistake is rarer and just as costly: running only page-level web analytics inside a product, then being unable to answer why people stop using it.

A SaaS company needs both, on different halves of the same domain.

The actual difference between the two categories

Web analytics answers questions about pages: who arrived, where from, what they read, whether they stayed. It works out of the box because pages are self-describing, and it costs a kilobyte.

Product analytics answers questions about people over time: of those who did A, how many went on to do B, how long did it take, which cohort are they in, and which early behaviour predicts whether they are still here in week four. It requires a designed event taxonomy, it costs tens of kilobytes, it sets cookies by design because following identified users across sessions is the entire point, and it needs somebody whose job includes using it.

Neither substitutes for the other. Asking a web analytics tool about week-four retention is futile; asking a product analytics platform how your blog is doing is forty kilobytes of overkill.

The arrangement that works

Draw the line at the login.

On the public side, the marketing site, the blog, the pricing page and the docs, use a lightweight cookieless tool. No consent banner in front of your acquisition funnel, no payload competing with your largest contentful paint, and honest numbers for the pages your growth actually depends on.

Behind the login, use a product analytics platform. You already have an account relationship and usually consent, the identity you need is a real user ID rather than a guessed one, and the questions are genuinely the ones these tools are built for.

This is not a compromise between two options. It is what a well-run SaaS measurement stack looks like, and it is cheaper than either tool used for both jobs.

The event taxonomy is the whole project

Product analytics succeeds or fails on the event design, not the tool. Agree the events before you implement them, keep them in version control next to the code, use object then past-tense verb naming, and put variable parts in properties rather than in event names.

The common failure is a taxonomy that grows without pruning until four events mean roughly the same thing and nobody trusts the reports. The second most common is autocapture used as a substitute for thinking, which produces an enormous undifferentiated stream and moves the governance problem from instrumentation time to analysis time without reducing it.

Heap's retroactive definition is the genuine innovation here, letting you define an event today and apply it to months of history, which removes the cost of having failed to predict a question. It is the strongest argument for autocapture that exists.

Choosing between the platforms

The free tiers are generous enough that you can evaluate two properly before paying for either, which is unusual in enterprise software and worth exploiting.

PostHog if you would otherwise buy four tools, because analytics, replay, flags, experiments, error tracking and surveys behind one signup is a materially faster loop than four procurement requests. Mixpanel if the priority is that everybody can read a funnel without training, and unlimited seats matter more than breadth. Amplitude if somebody's job is analysis and they will genuinely use behavioural cohorts and path analysis. Statsig if the central question is causal rather than descriptive, particularly with its warehouse-native mode where events never leave your infrastructure.

The options, at a glance

Tools covered on this page, ordered by my overall score. Prices read 11 September 2026.
ToolFromFree tierCookiesScore
PostHogFree then usage-basedYes, and it is the most generous on this listYes, by default7.1
MixpanelFree then usage-basedYes, 1M events a month with unlimited seatsYes, by default6.5
AmplitudeFree then event-basedYes, 2M events a monthYes, by default6.4
StatsigFree then usage-basedYes, and unusually largeYes, by default6.3
Absolutely Analytics$9 per monthNo free tier. A 30-day trial of the exact tier you pickedNone, so no consent banner8.9
HeapFree then quotedYes, with a session limitYes, by default5.8

The rest of the field

PostHog

7.1/10Product and event analytics

Analytics, replay, flags, experiments, error tracking and surveys behind one signup, open source and self-hostable, with a free tier the company says 97 per cent of its customers never exceed.

From Free then usage-based · Yes, by default · Full review →

Mixpanel

6.5/10Product and event analytics

The clearest funnel and retention reports in the category after sixteen years of refinement, with unlimited seats on every plan including free.

From Free then usage-based · Yes, by default · Full review →

Amplitude

6.4/10Product and event analytics

The deepest behavioural analysis here, 2 million events a month free with the whole platform included, and unlimited seats. The steepest learning curve too.

From Free then event-based · Yes, by default · Full review →

Statsig

6.3/10Product and event analytics

Experimentation first with analytics attached, plus a warehouse-native mode that computes results against your own Snowflake or BigQuery.

From Free then usage-based · Yes, by default · Full review →

Absolutely Analytics

8.9/10Privacy-first and cookieless

The other half of the stack: the public marketing site, where a product analytics payload and a consent banner are pure cost.

From $9 per month · None, so no consent banner · Full review →

Heap

5.8/10Product and event analytics

Autocapture with retroactive event definition, so a question asked today can be answered with months of history you never thought to instrument.

From Free then quoted · Yes, by default · Full review →

Common questions

What is the difference between web analytics and product analytics?

Web analytics answers questions about pages and costs a kilobyte. Product analytics answers questions about identified people over time, needs a designed event taxonomy, costs tens of kilobytes, sets cookies by design and requires an owner. Neither substitutes for the other, and most SaaS companies need both on different halves of the domain.

Should I use PostHog on my marketing site?

Generally no. The script is tens of kilobytes, it sets cookies so a consent banner applies in the UK and EU, and the product questions it unlocks are ones a marketing site does not have. Use a lightweight cookieless tool on the public side and PostHog behind the login.

Which product analytics tool has the best free tier?

Amplitude on volume, at 2 million events a month with the whole platform included and unlimited seats. PostHog on breadth, at 1 million events plus 5,000 replays, 1 million feature flag requests and 100,000 exceptions monthly. Mixpanel gives 1 million events with 10,000 replays and unlimited seats.

Do I need an event taxonomy before installing product analytics?

Yes, and it is most of the work. Agree the events first, keep the list in version control next to the code, name them object then past-tense verb, and put variable parts in properties. Implementations that skip this produce data nobody trusts within six months.

Related guides

Everything above is my own opinion, formed from published vendor documentation and pricing read on 11 September 2026. There are no affiliate links on this site and no vendor has paid to appear. Corrections welcome.