PostHog vs Flagsmith
Open source product analytics — all-in-one dev tool
vs. Open-source feature flags + remote config — SaaS, private cloud, self-host
Pricing tiers
PostHog
Free (generous)
No credit card. Each product has its own free monthly quota. Great for startups + OSS.
Free
Paid (usage-based)
Pay only what you use, after free quotas. Volume discounts at higher tiers. 6 projects, 7-year retention.
$0 base (usage-based)
Self-Hosted (OSS)
MIT-licensed. Run on your own infra via Docker/k8s. Zero vendor lock-in.
$0 base (usage-based)
Enterprise
Custom. SAML SSO, dedicated CSM, custom SLA.
Custom
Flagsmith
Free
$0. 50,000 API requests/mo. 1 team member. Unlimited flags. Community support.
Free
Self-hosted
$0 (OSS). Host yourself via Docker/K8s. Fair-source license (non-compete).
$0 base (usage-based)
Start-up
$40/mo. 1,000,000 API requests/mo. 3 team members. Standard support.
$40/mo
Scale-up
$200/mo. 5,000,000 API requests. 10 team members. Priority support + SLA.
$200/mo
Enterprise
Custom. Unlimited API requests, SSO, SAML, RBAC, audit logs, on-prem.
Custom
Free-tier quotas head-to-head
Comparing free on PostHog vs free on Flagsmith.
| Metric | PostHog | Flagsmith |
|---|---|---|
| data warehouse rows | 1000000 rows/month | — |
| error tracking exceptions | 100000 exceptions/month | — |
| feature flags requests | 1000000 requests/month | — |
| llm analytics events | 100000 events/month | — |
| logs gb | 50 GB/month | — |
| product analytics events | 1000000 events/month | — |
| projects | 1 projects | — |
| retention years | 1 year | — |
| session replay recordings | 5000 recordings/month | — |
| surveys responses | 1500 responses/month | — |
| team members | unlimited members | — |
Features
PostHog · 14 features
- A/B Testing — Experiments with significance analysis.
- Data Pipelines — Export events to BigQuery, Snowflake, S3.
- Data Warehouse — Query external sources (Stripe, Hubspot, S3) alongside events with SQL.
- Error Tracking — Sentry-style error tracking in same platform.
- Feature Flags — Rollout flags with targeting, A/B testing, JSON payloads.
- LLM Analytics — Tracing + cost tracking for OpenAI, Anthropic, Gemini, etc.
- Logs — Centralized log ingest with free 50 GB/month.
- Product Analytics — Events, funnels, trends, retention, paths. SQL insights available.
- Revenue Tracking — Integration with Stripe for revenue + churn metrics.
- Self-Hosting — Docker/Helm. Full feature parity with cloud.
- Session Replay — Watch user sessions. Privacy controls, masked inputs, JS errors.
- SQL Query API — Run ClickHouse SQL over your events via API.
- Surveys — In-app surveys + feedback widgets.
- Workflows — Trigger emails/webhooks on events.
Flagsmith · 14 features
- A/B Testing — Multivariate flag splits.
- Audit Log — Full history of flag changes.
- Change Requests — Approval workflow for flag changes.
- Edge API — Global low-latency flag eval.
- Feature Flags — Boolean + multivariate + JSON flags.
- Local Evaluation — Server SDKs eval flags locally — no per-req API call.
- Percentage Rollouts — Gradual traffic ramp.
- Remote Config — Non-boolean config values.
- Role-Based Access — Fine-grained permissions.
- Scheduled Flags — Time-based flag changes.
- Segments — Rule-based targeting.
- Self-Hosting — Docker/Helm install.
- SSO + SAML — Enterprise SSO.
- Webhooks — Outbound event streaming.
Developer interfaces
| Kind | PostHog | Flagsmith |
|---|---|---|
| CLI | — | Flagsmith CLI |
| SDK | posthog-android, posthog-flutter, posthog-go, posthog-ios (Swift), posthog-js, posthog-node, posthog-php, posthog-python, posthog-react-native, posthog-ruby | flagsmith-android, flagsmith-go, flagsmith-ios, flagsmith-java, flagsmith-js (browser), flagsmith-nodejs, flagsmith-python, flagsmith-ruby |
| REST | PostHog REST API | Flagsmith REST API |
| MCP | PostHog MCP | — |
| OTHER | Webhooks + Actions | Flagsmith Dashboard, Flagsmith Webhooks |
Staxly is an independent catalog of developer platforms. Outbound links to PostHog and Flagsmith are plain references to their official websites. Pricing is verified against vendor pages at publication time — reconfirm before buying.
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