What Is PostHog?
LibraryPostHog is an open-source product-analytics platform combining event tracking, session replay, feature flags, A/B experiments and surveys, available as a cloud service (US/EU) or self-hosted. It is popular with startups and developer-led companies, and several AI app builders wire it in by default.
Detect PostHog on any website:
Why PostHog Matters
Libraries and third-party services are where a site's real behaviour lives: analytics, payments, auth, UI components and animation all arrive as scripts the browser can see. Knowing that PostHog is on a page tells you about its dependencies, its privacy footprint, and sometimes its build pipeline — and it helps you tell template-driven stacks from hand-assembled ones. We've fingerprinted PostHog on 25 live sites in our database, so the answers here are grounded in real scan data — not marketing copy.
Does PostHog Mean a Site Was Built With AI?
PostHog on its own does not prove AI involvement.
Says nothing about who or what built the site.
How this feeds the score: builder fingerprints, bundle artifacts and AI-tool traces are weighed separately from stack context like frameworks, libraries and hosting. The full breakdown is on How scores work.
How Websites Using PostHog Work
- `posthog.init('phc_…', { api_host: 'https://us.i.posthog.com' })` snippet or the `posthog-js` package
- Events sent to app.posthog.com, eu.i.posthog.com or a reverse-proxied first-party path
- Session replay and feature-flag calls in the same SDK
- A product-analytics choice; neutral on authorship
Best Practices When Working With PostHog
Based on patterns in our scan dataset and the detection evidence tiers.
- →Start by running a PostHog detection scan on any URL you're evaluating — the 80+ signal engine returns a confidence score plus the exact markers it matched, which beats reading view-source by hand.
- →Cross-check the result against the full detection evidence in /how-scores-work — confidence tiers tell you whether a match is strong (headers + scripts) or circumstantial (a single HTML pattern).
How we detect PostHog — see our methodology: AI Influence Score calculation, evidence tiers, and fingerprint signal types.
How Our Detector Identifies PostHog
Our scanner analyzes multiple layers of a website's technical fingerprint to detect PostHog usage.
- Script URLs or inline script content matching "app.posthog.com", "eu.posthog.com", "us.posthog.com" (high-confidence tier)
- HTML structure patterns such as "posthog.init" (medium-confidence tier)
- Signal weights for PostHog: 90 points per high-tier match, 60 per medium, 30 per low — a site needs 60+ points before PostHog is reported.
Websites Built With PostHog
Real sites detected by our scanner
What PostHog Sites Usually Run Alongside
Technologies detected on the same domains as PostHog in our most recent scans. Counts are unique domains, not page views.
Frequently Asked Questions About PostHog
What is PostHog?+
PostHog is an open-source product-analytics platform combining event tracking, session replay, feature flags, A/B experiments and surveys, available as a cloud service (US/EU) or self-hosted. It is popular with startups and developer-led companies, and several AI app builders wire it in by default.
Does PostHog mean a website was built with AI?+
PostHog on its own does not prove AI involvement. Says nothing about who or what built the site.
Why does PostHog matter?+
Libraries and third-party services are where a site's real behaviour lives: analytics, payments, auth, UI components and animation all arrive as scripts the browser can see. Knowing that PostHog is on a page tells you about its dependencies, its privacy footprint, and sometimes its build pipeline — and it helps you tell template-driven stacks from hand-assembled ones. We've fingerprinted PostHog on 25 live sites in our database, so the answers here are grounded in real scan data — not marketing copy.
How do we detect PostHog?+
Our scanner checks for these signals: Script URLs or inline script content matching "app.posthog.com", "eu.posthog.com", "us.posthog.com" (high-confidence tier); HTML structure patterns such as "posthog.init" (medium-confidence tier); Signal weights for PostHog: 90 points per high-tier match, 60 per medium, 30 per low — a site needs 60+ points before PostHog is reported.. Each match contributes to a confidence score, and the full evidence tiers are documented at /how-scores-work.
How many websites using PostHog are in the database?+
We've fingerprinted 25+ live sites built with PostHog across our scan dataset. The list refreshes as new scans come in.
What are the typical characteristics of a PostHog website?+
`posthog.init('phc_…', { api_host: 'https://us.i.posthog.com' })` snippet or the `posthog-js` package. Events sent to app.posthog.com, eu.i.posthog.com or a reverse-proxied first-party path. Session replay and feature-flag calls in the same SDK. A product-analytics choice; neutral on authorship
Related Tools & Technologies
Other libraries and services we detect
Ready to put PostHog detection to work?
You now know what PostHog is, why it matters, how to spot it, and where the detection signals come from. The next step is using that knowledge on a real URL — yours, a competitor's, or a prospect's.