Companies Using Flagsmith

Flagsmith sells feature flags with an open-source core you can run on your own servers. Our October 2026 crawl finds its SDK on 673 domains, 2nd in our Feature Flags category. Before writing about who uses it, I loaded pages in a browser to see where the SDK calls home, read the environment keys it sends, and traced which script puts it on each page. Most of the list held up. Two platforms didn't, and we took them out.

Whose flags are they?

On 74 of the 800 raw domains, Flagsmith arrived inside Super Payments' checkout script. Super is a UK payment provider, and the dependency file its script loads contains the Flagsmith SDK, so the flags belong to Super. 54 of the 57 shops we could match to a company were British. Another 32 domains were apps built on Noloco, whose own Flagsmith account runs inside them, and 13 were archives hosted on Quartex. We removed them, 122 domains in all with three gambling or dead sites. What's left looks owner-held. Across the pages where we captured an environment key, we saw 47 different keys, and the only keys shared between domains stayed inside one company: UnitedHealthcare's plan sites, Cytiva's brands, Mekari and its Talenta product, LawnStarter and its sister brand.

Sales signal: for a payments company, the 74 removed shops are a ready list of Super Payments merchants. For anyone selling to Flagsmith users, this page's 673 is the list to use.

Cloud or self-hosted

Of 69 pages where we watched the SDK make its first call, 47 called Flagsmith's cloud API and 22 called an address the company runs itself. Mekari uses api-flagsmith.mekari.com, Freedom Mobile uses features.freedommobile.ca. UnitedHealthcare routes its calls through its own Medicare domain. That's about a third self-hosted or proxied, which matches how Flagsmith sells itself: its open-source page says the core is released under the BSD-3-Clause licence and will stay open.

"A third of the Flagsmith installs we watched call an address the company runs, not Flagsmith's own API. If you only count Flagsmith's API traffic, you miss them." - Elif Arslan, CMO & Co-founder at TechnologyChecker.io

Sales signal: a company running its own flag server has a platform team and a data-residency reason for it. Pitch infrastructure, compliance and observability tools there, not convenience.

A steady base

The chart starts at October 2026, because the cleaned count can only be measured on the current crawl. Since 16 March 2026, 147 domains have dropped Flagsmith, and 21 of them still run it on another hostname. Four customers own fleets: UnitedHealthcare's 39 plan sites, 15 Under Armour store domains, Onninen's 7 country sites and one machinery dealer's 6 are 67 domains but only four companies.

Sales signal: 673 domains, with those fleets counted once each, is the pool to size a campaign on.

Who the customers are

36.09% of matched companies with a known size have 1 to 10 employees, and 31.92% of those with a founding year started in the 2020s, a young base. Yet the named accounts are large. Jersey Mike's runs it on its main site, Cytiva across several of its brands, Sunrun on its customer portal and CoreWeave in its cloud console. UnitedHealthcare is the biggest single footprint, with 39 domains of Medicare, Medicaid and dual-eligible plan sites.

Sales signal: one UnitedHealthcare domain isn't 39 prospects. Count accounts by company before you count by domain, or your enterprise numbers will be inflated.

Finance and Europe

Software Development leads the industry chart at 17.78%, and Financial Services is second at 13.66%: OakNorth Bank, Xapo Bank, MeDirect, Xepelin and Endowus all run it on customer apps. The United States has 138 matched companies and the United Kingdom 41. France, the Netherlands, Germany and Switzerland add 55 between them.

Sales signal: regulated fintechs that self-host feature flags are a strong fit for compliance, audit and release-governance tools.

LaunchDarkly is a different market

Our switching table for Flagsmith is empty. LaunchDarkly, the only like-for-like rival in the category, is on 44,398 domains, about 66 times more. Since March, 10 domains have run both at some point and 1 does today. The direction is 7 domains from Flagsmith to LaunchDarkly against 2 the other way, but at that size it's noise. The rest of the category, Beamer (604) and LaunchNotes, announces releases rather than controlling them.

"Flagsmith and LaunchDarkly hardly ever share a site. Teams pick one model, open-source and self-hosted or fully managed, and stay with it." - Elif Arslan, CMO & Co-founder at TechnologyChecker.io

Sales signal: LaunchDarkly's sellers should look at Flagsmith's cloud users, not its self-hosters. A self-hosted team chose not to pay for managed flags.

The stack around it

Next.js runs on 40.27% of the 673 domains, Express on 7.43% and Nuxt.js on 5.79%. Google Analytics is on 66.27%. Adobe Experience Manager (6.54%) and Adobe Analytics (5.65%) mark the enterprise sites, and Webflow (10.7%) the marketing ones.

Sales signal: pair Flagsmith with Next.js in your filters to find product engineering teams with modern release practices.

What it costs

Flagsmith's pricing page (16 October 2026) lists a Free plan with 50,000 requests a month, Start-Up at $45 a month ($40 billed yearly) for a million requests, and Scale-Up at $300 ($250 yearly) for five million. Enterprise adds private cloud and supported self-hosting. Extra requests start at $50 per million.

Sales signal: request-based pricing means traffic growth turns into a bill. Fast-growing consumer apps on the cloud plans are the accounts most likely to look at self-hosting or a rival.

Key takeaways

1. 673 domains in October 2026, after removing 122 that carry Super Payments', Noloco's or Quartex's code.

2. About a third of the installs we watched call a self-hosted or proxied server.

3. A young, small-company base with real enterprise users: Cytiva, Sunrun and Jersey Mike's.

4. Financial services is the second industry at 13.66%.

5. Almost no overlap with LaunchDarkly, which is 66 times larger.

How to use this list

Group domains by company, then filter by industry and country. For the full list of 673 Flagsmith domains with company, size and stack data, explore TechnologyChecker.io.