# Mimic, Multilogin's Chromium, and its core numbers > 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. Source: https://mosaicbrowser.com/blog/mimic-core-versions ## Mimic, Multilogin's Chromium, and its core numbers 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. ![A core number is a Chrome major with a date, beside a screenshot: mosaic settings showing the installed Tesseract Chrome engine and its version](https://mosaicbrowser.com/covers/mimic-core-versions.webp) Mimic is Multilogin's Chromium-based browser, and each Mimic core is numbered after the Chrome major version it is built from. The [release notes](https://multilogin.com/release-notes/) list them one line at a time ("Mimic got the new … core"), and the [help page on core updates](https://multilogin.com/help/en_US/core-updates-and-how-they-work) says a profile picks up the newest tested core the next time it starts. So the version question has a simple shape. Read the core number, find the day it shipped, and put it next to the day that Chrome major reached the stable channel. The other core, Stealthfox, is Firefox-based and frozen on its last version, which is a separate problem with [its own write-up](https://mosaicbrowser.com/blog/stealthfox-legacy). This piece is about the one that still moves. ## What a Mimic core number tells you A core number is a claim about the engine underneath. If the number matches a Chrome major, the build should parse, render and negotiate the way that Chrome release does, and its User-Agent and client hints should say that major too. It does not tell you what the vendor changed inside the build. Every anti-detect engine is stock browser source plus the vendor's own changes, and the number only names the source half. Two engines both labelled with the same major can still disagree with real Chrome in different places, depending on what each vendor patched and what it left alone. 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) ## Lining a Mimic core version up against Chrome stable The number on its own answers nothing. A core only ages relative to the Chrome that real people are running, so the useful figure is the gap in days. 1. Take a core line from Multilogin's release notes and note its date. 2. Look up the date that Chrome major went to the stable channel on Google's Chrome Releases blog. 3. Subtract. That is how long Mimic profiles reported the previous major while stable Chrome was already on the new one. 4. Repeat for the next core, and the one after. One gap is an anecdote; a column of them is how the vendor actually works. Multilogin's own help page says it holds each Chrome release back to test it before shipping the matching core, so a gap is expected, and the page treats a Mimic version behind Chrome as normal. The table you build tells you whether the gap stays a few days or stretches. ## Why a few days is fine and a release cycle is not Chrome does not move everyone to a new major on one morning. Google rolls stable out in stages, and a large share of real Chrome stays on the previous major for days after the release. A core that lands inside that window is reporting a version plenty of real visitors still report. Chrome ships a new major roughly every four weeks, though. A core that misses a whole cycle is then a full major behind on the day the next one comes out, and the share of real visitors on that version keeps falling under it. Nothing breaks on a given day. The crowd the profile hides in just gets smaller and stranger. ## The number has to agree with everything else A page does not need to trust the version string. Each Chrome major changes things a script or a server can read: the APIs a page can find, the TLS hello the browser sends, how it orders headers. So a core number is only as good as the engine's agreement with it. A build that says one major and behaves like another is a contradiction, and a contradiction is stronger evidence than an old version ever was. We wrote up two of the places this shows: [JA4 moves with the Chrome major](https://mosaicbrowser.com/blog/ja4-moves-with-the-chrome-major), and the [twenty API entries where plain Chromium and Google's Chrome differ](https://mosaicbrowser.com/blog/twenty-apis-chrome-lacks) even at the same version. That second one is a lesson about what you line the number up against, too. Our own comparison against a stock browser had been green for weeks against Chrome for Testing, Google's unbranded build, and the twenty differences only appeared when the baseline became the branded Chrome people actually run. Matching the major is necessary. It is not the same as matching Chrome. ## How we track Chrome with Tesseract Chrome Mosaic has one engine, Tesseract Chrome, built from stock Chromium source with our patch series on top, and it follows the current stable Chrome major. We do the same subtraction on ourselves. Our last move to a new major cost 93 minutes of near-full rebuild on our build Mac; changing one patch afterwards is an incremental build of one or two minutes. Our comparison against a real Chrome refuses to run when the two are on different majors, because comparing one release with the next measures Google's changes, not ours. If you are choosing between engines, ask each vendor the same question: what was the gap, in days, for the last few majors? [Mosaic vs Multilogin](https://mosaicbrowser.com/compare/mosaic-vs-multilogin) sets out the wider differences, local engine against cloud platform. ## Questions ### What is a Mimic browser core? Mimic is Multilogin's Chromium-based browser. A core is one build of it, and Multilogin names each core by the Chrome major version it is built from, so a core numbered the same as a Chrome release carries that release's engine. ### How do I see which Mimic core a profile runs? Open chrome://version inside a running Mimic profile, or read the Chrome number in its User-Agent. That is the major a page sees, and it is the number to line up against Chrome's stable releases. ### Why is my Mimic version behind the latest Chrome? Multilogin's help page says it tests each Chrome release before shipping the matching Mimic core, so a new core arrives some days after Google's. A short gap like that sits inside Chrome's own staged rollout; a gap of a whole release cycle does not. ### Can I update a Mimic core myself? No. Multilogin's help page says cores are rolled out by Multilogin after testing and applied the next time you start a Mimic profile. ## Related [Multilogin froze Stealthfox, and what a legacy engine means](https://mosaicbrowser.com/blog/stealthfox-legacy): 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. [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. [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. [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. ## 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.