# Multilogin froze Stealthfox, and what a legacy engine means > Multilogin lists Stealthfox as a legacy core and points users to Mimic. A browser core that stops updating turns its own version into a signal. Source: https://mosaicbrowser.com/blog/stealthfox-legacy ## Multilogin froze Stealthfox, and what a legacy engine means Multilogin lists Stealthfox as a legacy core and points users to Mimic. A browser core that stops updating turns its own version into a signal. ![Mimic versus Stealthfox, each name in its own tile: Multilogin froze Stealthfox](https://mosaicbrowser.com/covers/stealthfox-legacy.webp) Multilogin calls Stealthfox, its Firefox-based browser core, legacy. Its [release notes](https://multilogin.com/release-notes/) and its [help page on the two cores](https://multilogin.com/help/en_US/how-to-use-mimic-and-stealthfox) point users to Mimic, the Chrome-based core, and say the Firefox one will not get new versions. Existing profiles still open. What changes is that the browser they imitate keeps moving and they do not. ## What a legacy Stealthfox core means An anti-detect browser's core is a modified build of a real browser. Each time the real browser ships a new major, the vendor rebases its changes onto the new source, rebuilds and ships a new core. Firefox and Chrome both put out a new major roughly every four weeks, so this is monthly work, and it never ends. Legacy means that work has stopped. Nothing is broken on the day a core is frozen. The problem grows one release at a time. Mosaic is a desktop app Email yourself the link and open it on your computer. [How it works: Its own Chromium](https://mosaicbrowser.com/features/engine) ## Why a frozen version becomes a signal Real browsers update themselves, so the share of visitors on any one old version shrinks with every release after it. A frozen core sits on its last version while that share drains away underneath it. The version string alone does not mark anyone, but the profiles left on it end up in a smaller and smaller crowd, and that crowd is increasingly made of browsers that never update. A core can claim a newer version than it is. That only moves the problem. A page does not have to trust the User-Agent; it can test for the features each release added. A browser that says it is a newer Firefox and lacks what that version shipped has contradicted itself in a few lines of script, and the contradiction is stronger evidence than an old version ever was. The same holds below JavaScript. The TLS hello a browser sends changes with its releases, which is why [JA4 moves with the Chrome major](https://mosaicbrowser.com/blog/ja4-moves-with-the-chrome-major): a version claim also has to agree with the handshake underneath it. And "no fixes" covers the fingerprint work too. When a detector learns to read a new surface, an active core gets a patch. A frozen one does not. ## Why the vendor tells you to move Two cores means every fingerprint change done twice, in two codebases with different internals. Firefox and Chromium differ in how they draw canvas, report WebGL, list fonts and shape their network traffic, so very little transfers. Keeping a second engine current is a second monthly rebase. Multilogin has chosen to spend that effort on Mimic and asks its users to follow. If you run Stealthfox profiles, the practical reading is the one Multilogin gives: export them and plan the move before the version gap gets wider. ## What keeping one engine current costs us We made the same choice from the other end. Mosaic has one engine, Tesseract Chrome, built from stock Chromium source with our patches on top, and no Firefox core. That is a real limitation if your work needs Firefox profiles, and the [Multilogin alternatives roundup](https://mosaicbrowser.com/compare/multilogin-alternatives) compares the other products, engines included. Staying current is the job we did not want to have twice. We timed our last move to a new Chrome major: 93 minutes for the near-full rebuild a version bump costs, against one or two minutes for an incremental build after changing a single patch. Our comparison against a real browser refuses to run across two majors, because comparing one major with the next measures the release, not our changes. So every new major means running that comparison again, and it keeps finding things a version number would never show, such as [twenty API entries where a plain Chromium build and Google's Chrome differ](https://mosaicbrowser.com/blog/twenty-apis-chrome-lacks). ## Moving profiles out of Multilogin Mosaic's importer recognises a Multilogin export by its shape. It maps across the profile name, notes, proxy, start pages, cookies where the export carries them, and the fingerprint fields Multilogin recorded. The profiles land in Tesseract Chrome, a Chromium engine. The difference between the two products as a whole, local engine against cloud platform, is laid out in [Mosaic vs Multilogin](https://mosaicbrowser.com/compare/mosaic-vs-multilogin). ## Questions ### Do Stealthfox profiles still work in Multilogin? Existing Stealthfox profiles keep opening, but a legacy core gets no new versions. Multilogin points its users to Mimic, its Chrome-based core, so check its own help pages for the current state before you plan around it. ### What does a legacy browser core mean in an anti-detect browser? The vendor has stopped shipping new engine versions and fixes for it. Profiles keep opening, but every month the real browser it imitates moves on while the core stays on its last version. ### Why is an old browser version a fingerprint signal? Real browsers update themselves, so the share of visitors on any one old version shrinks every month. A profile that stays on it either reports that old version, or claims a newer one and lacks the features that version added. ### Can I move Multilogin profiles into Mosaic? Yes. Mosaic's importer recognises a Multilogin export by its shape and maps the name, notes, proxy, start pages, cookies where present, and the fingerprint fields Multilogin recorded. ## Related [Mosaic vs Multilogin: local engine or cloud platform](https://mosaicbrowser.com/compare/mosaic-vs-multilogin): Mosaic keeps every profile on your computer at one flat price. Multilogin syncs to its cloud, prices by profile count and adds cloud phones and teams. [Multilogin alternatives: six anti-detect browsers compared](https://mosaicbrowser.com/compare/multilogin-alternatives): Six Multilogin alternatives with prices checked on their own pages: Mosaic, GoLogin, AdsPower, Dolphin{anty}, Octo Browser and Kameleo, and who each one suits. [JA4 moves with the Chrome major, and that is not a tell](https://mosaicbrowser.com/blog/ja4-moves-with-the-chrome-major): Chrome 152 read t13d1517h2 and 153 read t13d1518h2: one TLS extension apart. Compare a JA4 only against a Chrome of the same major version. [Twenty APIs Chrome doesn't have: Chromium's field trials](https://mosaicbrowser.com/blog/twenty-apis-chrome-lacks): Unbranded Chromium runs its field-trial testing config at every launch. Against Chrome 153 that was 20 API differences, and one switch moved them all. [How far behind Chrome stable is your anti-detect browser?](https://mosaicbrowser.com/blog/anti-detect-chromium-version-lag): Real Chrome updates itself, so an engine a few majors old claims a browser almost nobody runs. Our move from 153 to 154 took a 93-minute rebuild. [Is Camoufox still maintained? Reading the repository](https://mosaicbrowser.com/blog/is-camoufox-maintained): Is Camoufox still maintained? Its repository answers better than forums do: compare the latest release's date and Firefox base with today's Firefox. [Junglefox and Chroma, Kameleo's two engines](https://mosaicbrowser.com/blog/kameleo-junglefox): Junglefox is Kameleo's Firefox-based engine, beside Chroma, its Chromium one. A Firefox profile needs an engine that really is Firefox, and keeping one is work. [Mimic, Multilogin's Chromium, and its core numbers](https://mosaicbrowser.com/blog/mimic-core-versions): A Mimic core number is the Chrome major it is built on. Set the date a core shipped against the date that Chrome major reached stable, and you have the lag. ## Mosaic, on your own computer The browser this blog is about: its own Chromium, fingerprints from real machines and a proxy exit per profile. Free holds 3 profiles. Pro is $49 a month for any number. Mosaic is a desktop app Email yourself the link and open it on your computer.