The 3 Best Self-Hosted Feature Flag Tools in 2026, and Where "Free" Actually Ends

“Self-hosted feature flags” sounds like a solved problem - pick an open-source tool, run it, done. It isn’t, and the reason is that “open source” and “free” and “self-hostable” are three different claims, and each of these tools honors them to a different degree. One paywalls single sign-on. One needs a data warehouse before it does anything useful. All three cost real DevOps time the license doesn’t mention.

Here’s how I judged them. The license - how permissive, and what it lets you do. What the open-source build actually includes versus what’s gated behind a paid tier. Deployment options, including whether air-gapped is supported. The tech stack and ops burden, because that’s the true cost of “free.” And the job it’s built for - pure flags, or flags plus experimentation.

The short version

Tool	License	OSS build includes	Gated behind paid	Stack
Flagsmith	BSD-3-Clause	Flags, remote config, segmentation, basic A/B, 15+ SDKs	Enterprise governance (list not fully published)	Django / Postgres
Unleash	AGPL-3.0	Flags, strategies, rollouts, kill switches, canary, basic A/B	RBAC, SSO, SCIM, extra environments	Node
GrowthBook	MIT core	Flags plus full warehouse-native stats engine, unlimited users	Visual editor, bandits, SSO, SCIM	Needs your data warehouse

1. Flagsmith - the permissive, genuinely capable self-host

Flagsmith is the one I’d start most teams on. It’s licensed BSD-3-Clause - more permissive than the copyleft AGPL - and genuinely self-hostable via Docker, Kubernetes/Helm, on-prem and air-gapped. Crucially, the open-source build is a real product, not a crippled teaser: flags, remote config, segmentation, basic A/B testing and 15+ SDKs, with unlimited flags, environments and segments. Unlike PostHog’s officially-unsupported self-host, this is a supported self-hosting path. And if you’d rather pay for cloud convenience, the pricing is the most transparent in the category, starting at $40/mo annual.

The honest trade-offs. Running it in production is real DevOps - it’s a Django and Postgres stack that third-party comparisons call “tricky to get right,” and more resource-intensive than a Node or Go alternative. The team is small (roughly 12 people, bootstrapped, London), so the ecosystem is smaller than the giants’. A/B testing is basic, not a real statistical engine. And one caveat worth flagging: the exact list of features gated behind the paid Enterprise license isn’t fully published, so check with Flagsmith directly before assuming a specific governance feature is in the open build. For open-source flags without lock-in, Flagsmith is the standout.

2. Unleash - the mature name, with a paywall to watch

Unleash is usually the first name people reach for when they want a self-hostable LaunchDarkly alternative, and for good reason. It’s AGPL-3.0-or-later, has an 11-year track record, roughly 13.7k GitHub stars, 15 official SDKs (25+ counting community), and a G2 of 4.7 across 122 reviews - one of the best-rated in the category. The open-source edition is genuinely useful: flag management, activation strategies, gradual rollouts, kill switches, canary and basic A/B via variants, all runnable including air-gapped. You keep your data and you sidestep MAU pricing entirely.

But read this before you build on it, because it’s the gotcha. RBAC, SSO/SAML, SCIM and extra environments are all gated to paid tiers - they’re not in the free AGPL build. A recurring review complaint is being surprised you can’t use SSO without moving to a paywall, and most orgs need SSO past a certain size. There’s also no read-only or viewer seat, so once PMs and QA need access, every one is a paid seat. And the paid Pay-As-You-Go tier isn’t cheap at $75 per seat per month with a 5-seat minimum, plus $5 per extra million API requests over the 53M included. Unleash is free if you can live inside the OSS feature set, and a real bill the moment you need enterprise access controls. Decide which side of that line you’re on first.

3. GrowthBook - self-host, if experimentation is the point

GrowthBook is the self-hosted pick when you want more than toggles. Its core is MIT-licensed and self-hosts with unlimited users for $0 (several directories sit under a separate commercial license). What sets it apart is that it’s warehouse-native - it queries the BigQuery, Snowflake or Databricks warehouse you already run rather than ingesting a copy of your events, so your analytics data never leaves your infrastructure. On top of flags it ships the deepest stats engine of the open-source tools: CUPED, sequential testing, Bayesian analysis, multi-arm bandits and SRM checks. It’s a Y Combinator company founded in 2020 with a reported $22.6M Series A.

The gotcha is dependency and difficulty. GrowthBook’s value is warehouse-native, so you must already have a properly instrumented warehouse - no warehouse, far less value. And the statistics have a genuine learning curve, with reviews citing an engineer-first UI and documentation that’s thorough but hard to navigate. The visual editor, bandits, SSO and SCIM are gated to Enterprise. If your goal is self-hosted flags plus rigorous experimentation and you have data maturity, GrowthBook is the best-value option. If you only need toggles, Flagsmith or Unleash will serve you faster.

So which one?

• You want the most permissive license and a genuinely capable OSS build - Flagsmith, if you can run a Django and Postgres stack.
• You want the most mature, community-proven self-host - Unleash, as long as you don’t need free SSO, RBAC or lots of read-only viewers.
• You want self-hosted flags plus real experimentation - GrowthBook, if you already have an instrumented warehouse and someone to own the stats.

One honest note that applies to all three: the license is free, the operation is not. You’re trading license dollars for engineering time on orchestration, databases, upgrades and scaling. For a team with DevOps capacity that wants no lock-in, that’s a great trade. For a team without it, the paid cloud tiers - which are cheap on Flagsmith and GrowthBook anyway - are usually the better call. Every price and license here was verified against each vendor’s own site on 26 July 2026, with full detail in our tool reviews.