VistaLover

I feared as much... As I wrote in my previous post, you should also set extensions.e10sBlocksEnabling;false ... but I told you to RESET that and restart the browser! This is quite ominous; it might indicate that the Mozilla devs have excluded Firefox installations on XP from being able to activate their e10s support the standard way; after searching Bugzilla for related bugs, I think I found it: [e10s] Block e10s on Windows XP Given that e10s is being blocked on XP, the only way to enable it (under XP) is to force-enable it, like @Mathwiz suggested: https://wiki.mozilla.org/Electrolysis#Force_Enable Hopefully, after a full browser restart, it'll work; if it isn't, I'm out of ideas TBH; but people on XP have indeed managed to make it work: http://wp.xin.at/archives/4103 (scroll down to chapter 2, Electrolysis / e10s; but don't use as high a process number (16) as in that article!) (More reading material: https://www.ghacks.net/2016/07/22/multi-process-firefox/ ) Cheers

@Dave-H Hi, I hope you had a nice Bank Holiday Monday! > The setting browser.tabs.remote.autostart.2 is also set to "true" Is that pref in bold? I don't have it currently in my FxESR 52.9.1 (32-bit) (buildID=20180905233201) copy; reset the pref and it should go away with the next restart... > dom.ipc.processCount = 1 That should be the default setting (not in bold) > browser.tabs.remote.force-enable = true You don't need that new pref per se, when existing prefs are set correctly; please, for the time being, reset it (and it should go away with the next restart) > browser.tabs.remote.autostart = true The default value is false, so if you've toggled it to true, the whole pref line should be in bold > I've still only got one process in Task Manager, no matter how many tabs I have open! Please load about:support and scroll a bit down to "Application Basics => Multiprocess Windows" It should report "1/1 (Enabled by user)"; if not, please post the exact message; if it's extensions related, I fear you fell prey to a blunder I committed in my previous post (now corrected!). When one (or more) of installed legacy extensions are not MPC-compatible, they'll block electrolysis (multiprocess mode, usually abdreviated to e10s), and a new pref will be created extensions.e10sBlockedByAddons;true To negate that pref you should set extensions.e10sBlocksEnabling to false Always restart the browser after modifying any process related pref Disclaimer: Force-enabling e10s when incompatible extensions are installed and active may introduce some instability to the browser behaviour; YMMV... Inside your Firefox ESR profile directory there should be an .ini file called extensions.ini ; with the browser closed, open it with a proper text editor and check whether a section labelled [MultiprocessIncompatibleExtensions] exists (if yes, it should contain a list of incompatible addon IDs; you can use the Extensions section of about:support page to identify the offending addons and you should probably disable them while conducting multiprocess experiments in your browser)... Cheers

Well, while what you suggested would indeed work for FxESR52, you need not create a new pref to initiate e10s; already existing prefs control multiprocess activation in the browser: browser.tabs.remote.autostart;false Toggling that pref (to true) and restarting the browser will enable e10s; in the event you have installed conflicting legacy extensions, you should also toggle (to false) the following pref: extensions.e10sBlocksEnabling;true (followed by a new browser restart) The number of additional processes can be manually configured via the following about:config pref: dom.ipc.processCount;1 The default value of 1 means that when e10s is enabled, one additional content process is spawned (two overall present in Task Manager); modify to 2 and you'll get three in total and so on... But the multiprocess support present in Firefox 52 (and UXP) is not that mature and increasing the value to high figures (>= 4) will probably result in adverse effects (e.g. I have experienced frequent crashes); also, the more processes you configure, the better CPU you should have (e10s works best with recent, powerful, hardware... ). JFYI, the Moonchild Productions developers are currently in the process of removing any multiprocess code still extant in their UXP code tree, as they do not endorse e10s; Pale Moon never supported e10s, the same fate awaits official Basilisk (and hence Serpent 52.9.0); this is being tracked in UXP issue #953

I could not reproduce this in Firefox 52.0.2/52.9.0esr/52.9.1esr, but I don't have NoScript installed either! But I can reproduce this behaviour in (latest) Serpent 52.9.0 (2019-05-03) if I disable javascript in the browser (about:config => javascript.enabled;false); when I then load linked page, it complaints about "requiring the use of scripts" (in red letters): but if I click the magnifying glass, lo and behold I am being redirected to https://www.microsoft.com/en-us/search?q= So, clicking the magnifying glass normally triggers JS code that the UXP browser can't handle , but removing JS out of the equation you get the redirection to MS's search portal ...

... Please understand I have nothing personal at you, you're just a typical example of the mindset exhibited by most help seekers; I also apologise if you felt personally offended, which wasn't my intention in the slightest; but do allow me to stick to my beliefs, which are properly expressed in the following (well known, I hope) saying: Give a hungry person one fish and he'll have his stomach full for a day; teach him how to fish himself, and he might never go hungry again... First of all, I do not consider myself a "software-pro" as you put it ; on the contrary, computing came quite late in my adult life and I was horribly clueless at first, having no-one in my immediate circles to help me towards that goal; many nights over many months over several years reading forums and receiving just minimal (usually) tips from more "educated" people on line was the way to get myself slightly more "comfortable" with computers and software and to this day there exist fields for which I unashamedly confess my total ignorance. Mind you, like you, I also had "more serious tasks than software-learning", but I did strive to find at least some personal time devoted to that It's only through educating oneself that the what-you-called "low-level" people will, over time, become "middle-level" people and even - why not? - "software-pros"; otherwise, those "low-level" people will forever remain in a help-leeching stage, seeking guidance for even the simplest of things in forum after forum after forum... ... and you're only seeing your own side of things, as a help seeker; don't you think the volunteers (not only here in this specific forum, elsewhere too...) offering the help have themselves more serious tasks to do than explaining things down to the finest detail to people not willing to do some of the needed work themselves? My stance on offering help is to give people the needed push towards the right direction (e.g. in the form of knowledge articles and related documentation), not hold them by the hand all the way to their final destination... To make it perfectly clear to those using the SSE variant of New Moon 27 (latest win32 build here), you need to download at least the MMX LAV files found here and, after decompressing, put them in NM27's installation directory (IOW, adjacent to main executable palemoon.exe); it is unclear from the instructions in the first page of this thread whether the standard LAV files (found here) would work with just SSE (but not SSE2) processors! ... Again, it should be self-explanatory if one cares to study already "provided" screenshot or even attempts to familiarise oneself with only the basics related to Developer Tools; but as we established, people need pre-chewed food spoon-fed to them: ... write .mp4 on the "Filter output" input field... ... and you are genuinely welcome...

... And that is (among other things) what I meant by saying: With version 0.1.1 you have a constant visual display of the number of tabs (both pinned and ordinary ones) open, and that number is being updated in real time whether you open a new one or close an existing one; no need at all to interact with the button (which I've placed in the far right of the tab bar itself). Once you let AMO update the extension to v1.4.0 (WE format), you end up with an implementation of the addon with what I regard as inferior functionality: by default, its toolbar button shows no tab number, until clicked that is... And again, as you found yourself, to update the number displayed after new tabs are opened / old ones are closed, you'll have to click, click, click... Not my cup of tea, thanks! Perhaps my wording was poor; the WE flavour of the addon (v1.4.0) might actually work as intended by its developer on Serpent 52 (and Firefox 52.9.1), so it's not a matter of Serpent's inferior WE API support in that sense; but the point I wanted to make is that if you let Serpent 52 contact AMO to check for addon updates, you might end up with unwanted updates being applied to some of them...

... On Serpent 52.9.0, it appears to be Javascript related (as Web Console and/or Browser Console would reveal): Clicking the Learn More link takes you to a MDN article: https://developer.mozilla.org/el/docs/Web/JavaScript/Reference/Errors/Not_a_function Possibly unsurprisingly (now that MS and Google have turned into best pals), clicking the magnifying glass works as expected in Google Chrome (51.0.2679.0 in my case): @roytam1: If it is reproducible in latest official Basilisk (52.0.2019.03.27), perhaps the bug should be reported to the official Pale Moon forum (but NOT by a Serpent 52 user), so that MCP are made aware and, hopefully, come up with a fix...

In UXP commit 33ebc88 , platform (i.e. Goanna) version was bumped to 4.2.0, so I think the Serpent52 repo packages starting with the quoted above (and including the latest one) should be renamed to properly reflect that change: basilisk52-g4.1.win32-git-20190427-3424afcca-xpmod.7z => basilisk52-g4.2.win32-git-20190427-3424afcca-xpmod.7z basilisk52-g4.1.win32-git-20190504-d9d9d1ed8-xpmod.7z => basilisk52-g4.2.win32-git-20190504-d9d9d1ed8-xpmod.7z (for brevity, only win32 packages mentioned here...) In its current incarnation, Serpent 52.9.0 is incapable of contacting AMO to check for installed WE updates; there are two about:config prefs that control extension updates, the first is the main one and the other is a fallback one, extensions.update.url extensions.update.background.url Due to MCP changes, currently both point to the Basilisk extension repository (ABO) : https://addons.basilisk-browser.org/?component=aus&reqVersion=%REQ_VERSION%&id=%ITEM_ID%&version=%ITEM_VERSION%&maxAppVersion=%ITEM_MAXAPPVERSION%&status=%ITEM_STATUS%&appID=%APP_ID%&appVersion=%APP_VERSION%&appOS=%APP_OS%&appABI=%APP_ABI%&locale=%APP_LOCALE%&currentAppVersion=%CURRENT_APP_VERSION%&updateType=%UPDATE_TYPE%&compatMode=%COMPATIBILITY_MODE% ABO does not contain any WE addons; to mitigate that, if WE addons (from AMO originally) are installed in Serpent 52.9.0, you should change the value of at least one of those prefs to point to AMO; e.g. in my installation I modified extensions.update.background.url to have a value of https://versioncheck.addons.mozilla.org/update/VersionCheck.php?reqVersion=%REQ_VERSION%&id=%ITEM_ID%&version=%ITEM_VERSION%&maxAppVersion=%ITEM_MAXAPPVERSION%&status=%ITEM_STATUS%&appID=%APP_ID%&appVersion=52.9&appOS=%APP_OS%&appABI=%APP_ABI%&locale=%APP_LOCALE%&currentAppVersion=%CURRENT_APP_VERSION%&updateType=%UPDATE_TYPE%&compatMode=%COMPATIBILITY_MODE% But in reality, the kind of WebExtensions compatible with Serpent 52 are, more often than not, previous/older versions that are not being updated and if they are, they (of course) target Quantum (Fx >=57.0) with its richer set of WE APIs (compared to the ones present in Serpent); so by contacting AMO you risk 1. Having a legacy extension installed in Serpent 52 get updated to a non-compatible WE version of it... (remember, even though Serpent may advertise itself to AMO as Firefox 52.x, it has only a subset of the WE APIs found in Fx 52 ). 2. Having a WE addon get updated to a non-compatible (WE) version of it. An example from my own usage is https://addons.mozilla.org/el/firefox/addon/tab-tally/versions/ The one version fully compatible with St52 is XUL v0.1.1 (you can find it in CAA); if you check for updates on AMO, you'll be updated to v1.4.0, of the WE flavour, that does not work as expected in St52! That is why I have configured Serpent to NOT auto-update installed extensions...

... YES, we know already! Please stop repeating yourself ad nauseam... As I wrote in my post: What is it exactly you don't understand? I think the saying "A picture is worth a thousand words" should have applied here... If you're not at all familiar with the browser's Developer Tools section, then educate yourself; basically, for the purposes of URL sniffin (detecting background URLs for media and other content), you really only need WebConsole (CTRL+SHIFT+K): https://developer.mozilla.org/en-US/docs/Tools/Web_Console ... and, on occasion, Network Monitor (CTRL+SHIFT+Q): https://developer.mozilla.org/en-US/docs/Tools/Network_Monitor Load https://winfuture.de/UpdatePack in a New Moon 27 tab; in that same tab, open WebConsole, filter for ".mp4" (without the quotes) and then reload the page, followed by clicking the play button in the embedded web player; the link to the video itself should appear (https://videos.winfuture.de/16838.mp4) Right clink the link; you can copy the link (and use whatever download manager/extension already installed to fetch it to disk) OR you can opt to open it in a new New Moon 27 tab; if you have set up the browser correctly (LAV filters provided by roytam1 for SSE-only processors), it should start to auto-play; right-click the video and an option is there to save/download it! (<Personal rant>: I acknowledge most people here offering guidance/help do so on a voluntary basis, out of the goodness of heart, sacrificing valuable personal spare time... I'm no different ; but what really aggravates me is the lack of willingness on the help-receiving parties to do some of the "homework" themselves, learning things along the way; it appears that most people expect to be spoon-fed like a one year old toddler, this attitude never promotes one's own knowledge </Personal rant>)

=> // For Amazon Prime videos (forces use of Microsoft Silverlight plug-in) pref("general.useragent.override.www.amazon.com","Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.9) Gecko/20100101 Firefox/45.9"); I don't have an Amazon Prime Video (paid) subscription, so take this cum grano salis, but it was reported in the (official) Pale Moon forums that Amazon have updated their framework to now require the DRM API and, thus, having WidevineCDM present, enabled and up-to-date (>= 1.4.9.xxxx) is a prerequisite (no Silverlight fallback is possible anymore... ): https://forum.palemoon.org/viewtopic.php?p=163937#p163937 FirefoxESR 52.9.0[1] comes with a deprecated WV version (1.4.8.903), so it won't work under Vista+ (for reasons already discussed elsewhere, WV won't work at all under XP). At least for Amazon Music, supposedly a posted SSUAO would allow (for the time being?) a fallback to using Adobe Flash Player NPAPI: pref("general.useragent.override.music.amazon.com","Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/12.0 Safari/605.1.15");

The (new) user preference name that should be input in the "New string value" pop-up field must NOT contain the last semicolon (;), it should just be general.useragent.override.whatismybrowser.com Do not edit pref.js file manually to create SSUAOs; ONLY use the native about:config editor as you were instructed in previous posts (mine and others')!!! As it has already been said to you, FirefoxESR 52.9.x DOES NOT CONTAIN ANY STOCK (default) SSUAOs, so it's quite natural that ANY SSUAO created in its about:config page should be labelled as user set (and thus appear in bold!); STOP looking at other people's images, if you can't tell yourself that the image there is from New Moon 28, which (and this has also been conveyed to you) DOES come with STOCK SSUAOs inside its config editor (which are non-bold when not modified, i.e. "default"). Please do exactly as you are being instructed, do not deviate one iota from my SSUAO guide (linked to also by @Mathwiz)! What you do with other about:config prefs (that control other aspects of the browser behaviour) should not be your focus in the SSUAO context! ================================ OT: I have a background of many years in education (Physics, Chemistry, Biology), I have to admit this is being one of my most hard "teaching" cases... No offence is meant towards the other party, I am simply lost as to how I can make this come across... I think I am done myself - assigning this to someone more able/patient at (over-)explaining things...

Don't you worry one bit! You're already very high in our admiration list (at least in mine, that is... ) for simply trying to target that OS...

... Both @Mathwiz and I have literally hand-held you in this... ; what I would suggest is temporarily quit trying, have a soothing drink or something and simply relax for a couple of hours... Then go back two or three pages in this thread and with a clear mind try to re-digest what has been already detailed in, hopefully, good English, sticking only to what is being documented in the posts and refrain, as advised already, from actions like trashing your current profile (via browser reset for instance); pay religious attention to about:config pref names, excluding typos... To re-enable SSUAOs in Firefox 52, only the program installation directory path is needed, don't mess with any of the browser profile files... By the looks of it, you have created the correct javascript files and placed them in the right locations; then, you only need access to the native config editor found in "about:config" tab - don't mess with the JS files or any other InstalDir and/or profile files! The about:support internal page will only display the GLOBAL user agent of the browser; that value would either be the stock browser value (e.g. Mozilla/5.0 (Windows NT 5.1; rv:52.0) Gecko/20100101 Firefox/52.0 on WinXP 32-bit) or the value of the user set pref general.useragent.override (if present)... SSUAOs do not show up in the User-Agent entry in about:support/Application Basics, but do show up further down, under the Important Modified Preferences section. SSUAOs take precedence over the GLOBAL user agent (be it stock or user set); as instructed numerous times, right-click in an empty space inside about:config and choose New => String ; rather than typing there long pref names/values, I advise you to first create the correct pref name and value (please, doublecheck!) inside a .txt document and then just copy-paste them in the suitable fields (New string value -> Enter string value); hopefully, you'll make it right!

I trust more people here are familiar with the English language, am I right? https://browser.360.cn/ee/en.html (JFYI, also reported on the Vista forum a while back... )

... Again , this is most probably due to the lack of a proper installer for the XP/Vista Interlink fork (Mail News); my advice again would be to install official Interlink on a supported OS (default installation location and 32-bit architecture would be preferable), export the written key as a .reg file and then merge it on your XP machine; sadly, I'm not interested in testing that e-mail client, but modify the paths accordingly if the Mail News fork doesn't advertise itself as "\Binary Outcast\Interlink"... In the above case, you can always modify yourself the "Winapp2.ini" file locally, since it's open source: https://github.com/MoscaDotTo/Winapp2/commit/ff1cb36 Just my 2 eurocents, of course (auguroni )... EDIT: By inspecting more closely your CCleaner screenshots, I can now see that indeed Mail News does create "\Binary Outcast\Interlink" directories, so you should be fine with a .reg file imported from, say, Win7 x86... EDIT2: Since you also keep Thunderbird installed, you can probably figure out yourself what subkeys should be contained under "HKLM\Software\Binary Outcast\Interlink" by extrapolating from "HKLM\Software\Mozilla\Mozilla Thunderbird"; shouldn't be hard to create needed entries yourself

... You don't need an extension in NM27 to download that video to disk; it is being served through HTTPS progressive streaming, so you can use the browser's native Web Console (inside Developer Tools) and filter for ".mp4" links while loading the embedded player: The screengrab is from New Moon 27.9.6 32-bit (the SSE2 compile, running on Vista SP2 x86; you should be able to get the video download link on your SSE compile under WinXP, too! ).

NO, as far as the WidevineCDM (or, in fact, the browser itself) is concerned; I thought it was clear in my detailed analysis... Stock Firefox browser (on XP or other Win OS) can't access media codecs via Direct Show (which is intended for a subset of Media Players); had that been the case, you wouldn't need going through hoops while installing and enabling Adobe Primetime CDM to achieve HTML5 MP4 playback on XP... And in the very remote possibility someone patched the browser to give it access to Direct Show filters/codecs, as stated, the WidevineCDM would still NOT WORK! I kindly ask that the "XP" people quit beating the dead horse that is Widevine on XP ; I empathise totally; pretty soon, us - very few - still on Vista will be in the same boat... In any case, if anything new crops up, I'm sure it will be shared...

... and all of this closes a circle "I" started in my first post in this thread: Not to toot my own horn, but...

is Primetime Decryption different to Widevine ?? yet I've the Primetime decription activated and widevine in the folder yet it is a no go how do i get the widevine to appear in firefox addons and activated the version I have of widevine is 1.4..8.903 and 1.4.8.1008 Amazon Prime videos use DRM (Digital Rights Management), that is full encryption of streams. Adobe Primetime was/is a deprecated (not valid anymore) CDM (Content Decryption Module), whose only current use is by Windows XP users to enable h264/aac (patented video+audio codecs) decoding for HTML5 media playback inside Firefox web browser. No media delivery service uses Adobe Primetime for the purposes it was originally made, that is to decrypt DRM'ed content! 99% of services that offer encrypted audiovisual content (Netflix, Amazon, Spotify and many other media portals like national TV sites all around the world) rely on the Widevine CDM (currently owned by Google) ; Widevine module is closed-source and connects in real-time (during media playback) to specialised licence servers (equally owned by Google) to acquire decryption keys. Google updates the Widevine modules and lic servers very often and the browser vendors have to follow close; unlike Adobe Flash player plugin, which can be updated independently from the browser, a certain browser version (be it Firefox or Chrome) can only support a certain type (called "interface") of the WV CDM; this is because support for a specific "version" of widevine is coded inside the browser's own code; updated versions of the CDM can't/won't work with older browser versions. Widevine in Firefox is being updated as the browser itself is (i.e. newer versions come with updated Firefox builds); in recent Chrome versions, one can manually update the module to the latest - but still supported - version via "chrome://components" internal page... In what concerns Widevine CDM and Windows XP, these two are indeed incompatible in the case of Mozilla-type browsers, because the CDM is coded in such a way that it only looks for (patented) decoders in the OS via Windows Media Foundation framework (WMF), a Windows feature that first appears in Windows Vista SP2; this is why the Mozilla devs have hidden the Widevine CDM from appearing inside about:plugins when the OS used is Windows XP! Even if you made it appear back (which would've required modifying the browser's code and recompiling), it would be totally useless under XP! (if Widevine were open-source, it could have been patched to look for decoders elsewhere, but, sadly for XP users, that's NOT the case!). In the case of Widevine CDM PPAPI in Google Chrome, there the module uses the patented codecs bundled with the browser, but the versions of Widevine (1.4.6.xxxx to 1.4.8.xxxx) supported in Chrome 49 (last WinXP compatible) are now severely outdated and will be denied access by licence servers; as such, they are simply not working anymore! As of this writing, minimum supported "version" of Widevine CDM, of any type (NPAPI/PPAPI), is 1.4.9.xxxx (version 1.4.9.1088 to be revoked at the end of May) - to my knowledge, no browser under XP has support for current valid Widevine versions! (Under Vista, the only browser that I know of that supports WidevineCDM is @roytam1's Serpent 52.9.0 (very recent builds), thanks to a gallant effort by the Moonchild team to restore partial support for WV v1.4.9.xxxx in official Basilisk; support for the next generation of WV ("interface" 10, versions 4.10.xxxx), currently in place in Firefox Quantum, is not there yet, so at the end of May Serpent's WV support under Vista+ may become broken, too...) For those that may want to read more on the WV subject: https://github.com/Feodor2/Mypal/issues/26#issuecomment-456969027 https://github.com/MoonchildProductions/UXP/issues/962

... Of course they are! But I was referring to the "\Capabilities\StartMenu" subkeys as displayed in my previous post https://msfn.org/board/topic/178355-missing-email-client-in-the-start-menu/?do=findComment&amp;comment=1162776 Does "Mozilla Thunderbird" have such a StartMenu subkey even on Windows 10? Not to worry; apart from English (and, of course, Greek ), I also speak (but not write well) French and my late father (God rest his soul) had studied in Torino; lots of Italian books exist in the family library, as a young kid I used to open and try to read them; I can now understand quite well written Italian (it has evolved from ancient Latin, of course, a common root shared between modern French, Spanish, Portuguese and, to a lesser degree, English...); but I'm certainly going off-topic with this... Saluti

New Moon 28 has a default SSUAO for "live.com" that flags it as Firefox/52.9 (Pale Moon): general.useragent.override.live.com;Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.9) Gecko/20100101 Firefox/52.9 (Pale Moon) OTOH, Serpent doesn't have this by default ; did you in fact modify the above SSUAO in NM28 to: general.useragent.override.live.com;Mozilla/5.0 (X11; Fedora; Fedora; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.86 Safari/537.36 ???

It depends on where you installed Mozilla Firefox on your system; the "installation" could have been a "proper" one via the provided installer; if you accepted default settings and the OS resides in the C drive, it should be in "C:\Program Files\Mozilla Firefox\" The above is for a 32-bit OS (well, actually it also covers 64-bit Firefox in a 64-bit OS, but that is out of scope here...) %ProgramFiles% env var should be used for non-default OS installations... If you changed the default location during installation, only you know where that is... Second scenario is for people that don't use an installer, but a zip package; I should include in this case people running so-called "portable" installations (in PAF or WinPenPack formats); in all these cases, Firefox installation directory is where the main executable, firefox.exe, resides! (The following is from a previous FirefoxESR 24.8.1 "proper" installation on my Vista laptop: )

Perhaps they're checking whether the browser is WebRTC enabled? Serpent does support it, whereas New Moon doesn't... WebRTC is, of course, required for audio/video calls, it shouldn't be required for simple messaging, but what do I know...???

... Not what the extension author claims, BTW: ... Elementary, my dear Watson! The addon is of the Web Extension type (since hosted on AMO currently), as such won't install/work in Pale Moon and forks... (NB: Screengrab was taken with latest Serpent 52.9.0; it has a default SSUAO for AMO general.useragent.override.addons.mozilla.org;Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.9) Gecko/20100101 Firefox/52.9 )

If you head over to about:support, you'll be able to see the global user-agent string of your Firefox browser: I can't tell whether it's a typo on your part, but override has 2 "r"s ! So, in order to spoof as Fx 53.0 on Win7, the name of the about:config "string" pref should read: general.useragent.override and its value: Mozilla/5.0 (Windows NT 6.1; rv:53.0) Gecko/20100101 Firefox/53.0 Setting that pref and restarting the browser, you'll be able to see the modified global UA string in about:support. Global UA means the same one is sent in the headers of all web requests; SSUAO (Site-Specific-User-Agent-Override) means a different to the global one is being sent when a web request is being made to the domain specified in the pref's name... If you followed my guide and enabled SSUAOs in FxESR 52.9.1, then to spoof as Fx 66.0 on Win7 to https://www.whatismybrowser.com/ you need create a "string" about:config pref with name general.useragent.override.whatismybrowser.com and value: Mozilla/5.0 (Windows NT 6.1; rv:66.0) Gecko/20100101 Firefox/66.0 For good measure, restart the browser after setting the above SSUAO (normally, it should work right-away...). I hope it's more clear now...