Flagcross
FLAGCROSS TRANSLATOR
Translate a feature-flag export between platforms without the file touching any server.
Paste a LaunchDarkly, Unleash, or Split export. Choose a target platform. Every rule the translator can map exactly comes through cleanly; every rule that changes — or cannot map at all — is named in your translation report, with the reason.
No server receives your feature-flag export. All processing happens in your browser.
How Flagcross processes your export
01 / A TRANSLATOR, NOT A SILENT CONVERTER
A percentage rollout, a user-segment rule and a prerequisite flag each mean something different on each platform. The differences are invisible until a flag behaves differently in production.
Teams migrating between feature-flag platforms do it by hand, flag by flag — because the exports look similar and are not. LaunchDarkly's percentage rollout operator is not Unleash's variant-gradual rollout. Split's user-segment targeting has no equivalent in a self-hosted service. A scripted search-and-replace catches none of this, and a manual review of a thousand flags misses the one rule that behaves differently.
Flagcross parses the source export, maps each rule to the target platform's equivalent, and produces a translation report in three parts — TRANSLATED for exact matches, APPROXIMATED for near matches with documented changes, and NOT TRANSLATABLE for rules that cannot map, with the reason.
02 / THREE CATEGORIES OF OUTPUT
Every rule in your export lands in exactly one category — and all of them are visible at once, listed in a ruled three-panel layout.
TRANSLATED
The rule and its equivalent. The flag maps 1:1 — same behaviour, same semantics, same result. No human judgement needed. You can deploy these flags without manual verification of their logic.
APPROXIMATED
The rule maps but not exactly. The target platform has no identical operator or constraint, so Flagcross finds the closest equivalent and documents what changes — a different rollout distribution, a narrower targeting scope, a missing prerequisite. These rules need a human review: the behaviour is close but not identical.
NOT TRANSLATABLE
The rule has no equivalent on the target platform, and Flagcross says why. No silent simplification, no dropped constraint, no invisible change. These rules must be redesigned for the new platform — but at least you know which ones, and why.
03 / WHAT IT COSTS
Free. No sign-up, no API token, no server-side processing. The tool is the page.
There is no paid tier, no usage cap, and no account required. Flagcross runs entirely in your browser — the export you paste is parsed, translated and presented without a single byte leaving your machine. The only thing the server does is serve the page itself.
For teams that need to process many exports or integrate Flagcross into a CI pipeline, the product's entire logic is client-side JavaScript. You can open the browser's developer tools, read every line of the translation code, and verify that no data is sent anywhere.
04 / WHAT IT DOES NOT DO
Limitations stated plainly — so you know what this tool is before you paste anything.
Does not connect to any flag platform
Flagcross does not read from LaunchDarkly, Unleash, Split, or any other service. There is no API key input, no OAuth flow, no webhook. You paste a file you already have; the tool converts it into a file you download. It never fetches anything.
Does not change a live flag
The translation is a static report. Flagcross has no credentials, makes no API calls, and has no way to write back to any platform. The output is a configuration file and a human-readable report — you decide what to do with them.
Does not store or transmit your export
All processing happens in a single JavaScript context in your browser. Refreshing the page clears everything. There is no server, no database, no localStorage persistence of your export data.
05 / YOUR DATA NEVER LEAVES YOUR BROWSER
No server receives your feature-flag export. That is not a promise — it is an architectural constraint.
A feature-flag export names internal services, customer segments, unreleased features, and rollout percentages that the business has not announced. Sending that to any third-party server — even a trusted one — creates a disclosure surface that a self-respecting platform engineer should not accept.
Flagcross is built as a single-page application with zero server-side processing. The export you paste is parsed by JavaScript running in your browser tab, translated by the same JavaScript, and the output is generated as a downloadable blob that never transits a network. The Worker that serves the page is a static-file host and nothing more.
What stays on your machine
The raw export, every parsed rule, the full translation report, all JSON representations.
What leaves your machine
Nothing. The page request. A single HTTP request for the HTML document. No data, no payload, no analytics beacon.
06 / WHY NOT DO IT BY HAND
A migration is the wrong time to discover what a platform did not say.
"My export is JSON. Can I just grep and sed the difference?"
A search-and-replace handles the things you already know to look for. The differences that surface in a flag migration are the things you do not know: a percentage rollout that LaunchDarkly evaluates as a bucket (deterministic) while Unleash evaluates as a random sample (non-deterministic for small populations); a prerequisite flag that Split evaluates before the target flag while the target platform evaluates both independently.
Flagcross knows the semantics of each platform's operators. It does not just rename keys — it tells you when the behaviour changes.
"I have a thousand flags. Can I trust an automated translation?"
Flagcross's output has three categories because the answer is different for different rules. TRANSLATED rules need no human review. APPROXIMATED rules name what changed and in what direction — you see the delta and decide. NOT TRANSLATABLE rules are listed with the reason, so you can plan a redesign for exactly those flags.
The report is provided as-is, and the download row includes an acknowledgement checkbox: "This translation is provided as-is. Verify converted rules in non-production before deploying."
"Does it support my platform combination?"
Flagcross translates between LaunchDarkly and Unleash formats, with more platform pairs under active development. Each platform combination produces its own rule mappings, and each rule pair is documented in the translation report. If your pair is not yet supported, the tool still parses the export and shows you what it found — the unsupported rules land in NOT TRANSLATABLE with the reason that no mapping exists for that platform target.
START TRANSLATING
Paste your export. See exactly what moves, what changes, and what needs your attention.
No server. No sign-up. No data leaves your browser. The translation completes in under a second for exports of hundreds of flags, based on client-side JSON parsing speed.