This is difference between the default preference of Firefox 68.0 beta 4 and one of 67.0.

Preference difference
PrefFirefox 67.0Firefox 68.0 beta 4
app.releaseNotesURLhttps://www.mozilla.org/%LOCALE%/firefox/%VERSION%/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-browser&utm_campaign=whatsnewhttps://www.mozilla.org/%LOCALE%/firefox/%VERSION%beta/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-browser&utm_campaign=whatsnew
app.update.url.detailshttps://www.mozilla.org/%LOCALE%/firefox/noteshttps://www.mozilla.org/%LOCALE%/firefox/beta/notes
app.update.url.manualhttps://www.mozilla.org/firefox/https://www.mozilla.org/firefox/beta
apz.fixed-margin-override.bottomundefined0
apz.fixed-margin-override.enabledundefinedfalse
apz.fixed-margin-override.topundefined0
browser.aboutHomeSnippets.updateUrlhttps://snippets.cdn.mozilla.net/%STARTPAGE_VERSION%/%NAME%/%VERSION%/%APPBUILDID%/%BUILD_TARGET%/%LOCALE%/%CHANNEL%/%OS_VERSION%/%DISTRIBUTION%/%DISTRIBUTION_VERSION%/undefined
browser.autofocustrueundefined
browser.contentblocking.features.strictundefinedtp,tpPrivate,cookieBehavior4,cm,fp
browser.contentblocking.maxIntroCountundefined5
browser.contentblocking.reportBreakage.enabledfalsetrue
browser.history.maxStateObjectSize6553602097152
browser.in-content.dark-modeundefinedfalse
browser.newtabpage.activity-stream.asrouter.providers.cfr{"id":"cfr","enabled":true,"type":"local","localProvider":"CFRMessageProvider","frequency":{"custom":[{"period":"daily","cap":1}]},"categories":["cfrAddons","cfrFeatures"]}{"id":"cfr","enabled":true,"type":"remote-settings","bucket":"cfr","frequency":{"custom":[{"period":"daily","cap":1}]},"categories":["cfrAddons","cfrFeatures"],"updateCycleInMs":3600000}
browser.security.newcerterrorpage.enabledtrueundefined
browser.tabs.remote.useHTTPResponseProcessSelectionfalsetrue
browser.urlbar.quantumbarfalsetrue
corroborator.enabledundefinedfalse
devtools.aboutdebugging.local-tab-debuggingundefinedfalse
devtools.aboutdebugging.networkfalseundefined
devtools.aboutdebugging.process-debuggingundefinedtrue
devtools.aboutdebugging.showHiddenAddonsundefinedfalse
devtools.aboutdebugging.showSystemAddonsfalseundefined
devtools.aboutdebugging.wififalseundefined
devtools.browserconsole.contentMessagesundefinedfalse
devtools.browserconsole.filterContentMessagesundefinedfalse
devtools.debugger.log-actionsundefinedfalse
devtools.debugger.prefs-schema-version1.0.01.0.9
devtools.inspector.flexboxHighlighter.combinefalseundefined
devtools.inspector.inactive.css.enabledundefinedfalse
devtools.netmonitor.har.defaultFileNameArchive %date%hostname_Archive [%date]
devtools.netmonitor.requestBodyLimitundefined1048576
devtools.recordreplay.timeline.enabledfalseundefined
devtools.webconsole.input.autocompleteundefinedtrue
dom.animations-api.core.enabledtrueundefined
dom.enable_performancetrueundefined
dom.enable_performance_navigation_timingtrueundefined
dom.enable_resource_timingtrueundefined
dom.event.handling-user-input-time-limit1000undefined
dom.forms.autocomplete.formautofillfalseundefined
dom.input.skip_cursor_move_for_same_value_settrueundefined
dom.keyboardevent.keypress.hack.dispatch_non_printable_keys.addlundefined
dom.keyboardevent.keypress.hack.use_legacy_keycode_and_charcode.addlundefined
dom.mouseevent.click.hack.use_legacy_non-primary_dispatchundefined
dom.performance.enable_notify_performance_timingfalseundefined
dom.placeholder.show_on_focustrueundefined
dom.popup_allowed_eventschange click dblclick mouseup pointerup notificationclick reset submit touchend contextmenuchange click dblclick auxclick mouseup pointerup notificationclick reset submit touchend contextmenu
dom.requestIdleCallback.enabledtrueundefined
dom.script_loader.bytecode_cache.enabledtrueundefined
dom.script_loader.bytecode_cache.strategy0undefined
dom.storage.next_genfalsetrue
dom.storage.snapshot_gradual_prefillundefined4096
dom.vr.openvr.action_inputfalsetrue
dom.vr.process.enabledundefinedfalse
extensions.abuseReport.enabledundefinedfalse
extensions.abuseReport.urlundefinedhttps://addons.mozilla.org/api/v4/abuse/report/addon/
extensions.getAddons.discovery.api_urlundefinedhttps://services.addons.mozilla.org/api/v4/discovery/?lang=%LOCALE%
extensions.htmlaboutaddons.discover.enabledundefinedfalse
extensions.htmlaboutaddons.inline-options.enabledundefinedfalse
extensions.webcompat-reporter.enabledfalsetrue
extensions.webextensions.performanceCountersMaxAge10005000
extensions.webextensions.restrictedDomainsaccounts-static.cdn.mozilla.net,accounts.firefox.com,addons.cdn.mozilla.net,addons.mozilla.org,api.accounts.firefox.com,content.cdn.mozilla.net,discovery.addons.mozilla.org,input.mozilla.org,install.mozilla.org,oauth.accounts.firefox.com,profile.accounts.firefox.com,support.mozilla.org,sync.services.mozilla.comaccounts-static.cdn.mozilla.net,accounts.firefox.com,addons.cdn.mozilla.net,addons.mozilla.org,api.accounts.firefox.com,content.cdn.mozilla.net,discovery.addons.mozilla.org,install.mozilla.org,oauth.accounts.firefox.com,profile.accounts.firefox.com,support.mozilla.org,sync.services.mozilla.com
extensions.webextensions.themes.icons.buttonsback,forward,reload,stop,bookmark_star,bookmark_menu,downloads,home,app_menu,cut,copy,paste,new_window,new_private_window,save_page,print,history,full_screen,find,options,addons,developer,synced_tabs,open_file,sidebars,share_page,subscribe,text_encoding,email_link,forget,pocketundefined
extensions.webextensions.themes.icons.enabledfalseundefined
features.normandy-remote-settings.enabledfalseundefined
fission.preserve_browsing_contextsundefinedfalse
fission.rebuild_frameloaders_on_remoteness_changeundefinedfalse
font.size.fixed.ar12undefined
font.size.fixed.el12undefined
font.size.fixed.he12undefined
font.size.fixed.ja16undefined
font.size.fixed.ko16undefined
font.size.fixed.th13undefined
font.size.fixed.x-armn13undefined
font.size.fixed.x-beng13undefined
font.size.fixed.x-cans13undefined
font.size.fixed.x-cyrillic12undefined
font.size.fixed.x-devanagari13undefined
font.size.fixed.x-ethi13undefined
font.size.fixed.x-geor13undefined
font.size.fixed.x-gujr13undefined
font.size.fixed.x-guru13undefined
font.size.fixed.x-khmr13undefined
font.size.fixed.x-knda13undefined
font.size.fixed.x-math13undefined
font.size.fixed.x-mlym13undefined
font.size.fixed.x-orya13undefined
font.size.fixed.x-sinh13undefined
font.size.fixed.x-tamil13undefined
font.size.fixed.x-telu13undefined
font.size.fixed.x-tibt13undefined
font.size.fixed.x-unicode12undefined
font.size.fixed.x-western12undefined
font.size.fixed.zh-CN16undefined
font.size.fixed.zh-HK16undefined
font.size.fixed.zh-TW16undefined
font.size.monospace.arundefined12
font.size.monospace.elundefined12
font.size.monospace.heundefined12
font.size.monospace.jaundefined16
font.size.monospace.koundefined16
font.size.monospace.thundefined13
font.size.monospace.x-armnundefined13
font.size.monospace.x-bengundefined13
font.size.monospace.x-cansundefined13
font.size.monospace.x-cyrillicundefined12
font.size.monospace.x-devanagariundefined13
font.size.monospace.x-ethiundefined13
font.size.monospace.x-georundefined13
font.size.monospace.x-gujrundefined13
font.size.monospace.x-guruundefined13
font.size.monospace.x-khmrundefined13
font.size.monospace.x-kndaundefined13
font.size.monospace.x-mathundefined13
font.size.monospace.x-mlymundefined13
font.size.monospace.x-oryaundefined13
font.size.monospace.x-sinhundefined13
font.size.monospace.x-tamilundefined13
font.size.monospace.x-teluundefined13
font.size.monospace.x-tibtundefined13
font.size.monospace.x-unicodeundefined12
font.size.monospace.x-westernundefined12
font.size.monospace.zh-CNundefined16
font.size.monospace.zh-HKundefined16
font.size.monospace.zh-TWundefined16
full-screen-api.allow-trusted-requests-onlytrueundefined
geo.wifi.urihttps://www.googleapis.com/geolocation/v1/geolocate?key=%GOOGLE_LOCATION_SERVICE_API_KEY%https://location.services.mozilla.com/v1/geolocate?key=%MOZILLA_API_KEY%
gfx.logging.slow-frames.enabledundefinedfalse
gfx.webrender.debug.texture-cache.disable-shrinkfalseundefined
gfx.webrender.split-render-rootsundefinedfalse
image.animated.generate-full-framestrueundefined
intl.hyphenate-capitalized.de-1901undefinedtrue
intl.hyphenate-capitalized.de-1996undefinedtrue
intl.hyphenate-capitalized.de-CHundefinedtrue
javascript.options.bigintfalseundefined
javascript.options.experimental.await_fixundefinedfalse
javascript.options.mem.nursery.min_kbundefined256
layout.css.contain.enabledfalseundefined
layout.css.getBoxQuads.enabledfalseundefined
layout.css.scroll-snap.enabledtrueundefined
lightweightThemes.recommendedThemes[{"id":"recommended-1","homepageURL":"https://addons.mozilla.org/firefox/addon/a-web-browser-renaissance/","headerURL":"resource:///chrome/browser/content/browser/defaultthemes/1.header.jpg","textcolor":"#000000","accentcolor":"#834d29","iconURL":"resource:///chrome/browser/content/browser/defaultthemes/1.icon.jpg","previewURL":"resource:///chrome/browser/content/browser/defaultthemes/1.preview.jpg","author":"Sean.Martell","version":"0"},{"id":"recommended-2","homepageURL":"https://addons.mozilla.org/firefox/addon/space-fantasy/","headerURL":"resource:///chrome/browser/content/browser/defaultthemes/2.header.jpg","textcolor":"#ffffff","accentcolor":"#d9d9d9","iconURL":"resource:///chrome/browser/content/browser/defaultthemes/2.icon.jpg","previewURL":"resource:///chrome/browser/content/browser/defaultthemes/2.preview.jpg","author":"fx5800p","version":"1.0"},{"id":"recommended-4","homepageURL":"https://addons.mozilla.org/firefox/addon/pastel-gradient/","headerURL":"resource:///chrome/browser/content/browser/defaultthemes/4.header.png","textcolor":"#000000","accentcolor":"#000000","iconURL":"resource:///chrome/browser/content/browser/defaultthemes/4.icon.png","previewURL":"resource:///chrome/browser/content/browser/defaultthemes/4.preview.png","author":"darrinhenein","version":"1.0"}]undefined
lightweightThemes.selectedThemeIDdefault-theme@mozilla.orgundefined
lightweightThemes.update.enabledtrueundefined
media.audiograph.single_thread.enabledundefinedfalse
media.navigator.enabledtrueundefined
media.peerconnection.capture_delay70undefined
media.peerconnection.enabledtrueundefined
media.videocontrols.picture-in-picture.enabledundefinedfalse
media.videocontrols.picture-in-picture.video-toggle.enabledundefinedfalse
media.videocontrols.picture-in-picture.video-toggle.flyout-enabledundefinedfalse
media.videocontrols.picture-in-picture.video-toggle.flyout-wait-msundefined5000
network.cookie.cookieBehaviorundefined4
network.cookie.lifetimePolicy0undefined
network.cookie.same-site.enabledtrueundefined
network.http.enforce-framing.strict_chunked_encodingundefinedtrue
network.http.tailing.enabledtrueundefined
network.ssl_tokens_cache_capacityundefined2048
network.ssl_tokens_cache_enabledundefinedfalse
network.traffic_analyzer.enabledundefinedtrue
network.trr.excluded-domainsundefinedlocalhost,local
network.trr.resolversundefined[{ "name": "Cloudflare", "url": "https://mozilla.cloudflare-dns.com/dns-query" }]
network.trr.wait-for-portaltruefalse
performance.adjust_to_machinefalseundefined
performance.low_end_machinefalseundefined
permissions.desktop-notification.postPrompt.enabledfalsetrue
prio.enabledfalseundefined
privacy.donottrackheader.enabledfalseundefined
privacy.trackingprotection.cryptomining.enabledundefinedtrue
privacy.trackingprotection.fingerprinting.enabledundefinedtrue
prompts.authentication_dialog_abuse_limit32
remote.enabledundefinedfalse
remote.force-localundefinedtrue
remote.log.levelundefinedInfo
security.certerrors.mitm.auto_enable_enterprise_rootsfalsetrue
security.remote_settings.intermediates.enabledfalsetrue
security.signed_content.CSP.defaultscript-src 'self'; style-src 'self'undefined
security.tls.enable_post_handshake_authundefinedfalse
security.webauth.webauthn_enable_android_fido2undefinedfalse
services.blocklist.onecrl.checked0undefined
services.blocklist.onecrl.collectioncertificatesundefined
services.blocklist.onecrl.signeronecrl.content-signature.mozilla.orgundefined
services.settings.changes.path/buckets/monitor/collections/changes/recordsundefined
services.settings.default_signerremote-settings.content-signature.mozilla.orgundefined
services.settings.security.onecrl.bucketundefinedsecurity-state
services.settings.security.onecrl.checkedundefined0
services.settings.security.onecrl.collectionundefinedonecrl
services.settings.security.onecrl.signerundefinedonecrl.content-signature.mozilla.org
services.sync.engine.bookmarks.bufferfalsetrue
services.sync.engine.bookmarks.validation.enabledundefinedtrue
services.sync.engine.passwords.validation.enabledundefinedtrue
services.sync.prefs.sync.browser.contentblocking.features.strictundefinedtrue
services.sync.prefs.sync.lightweightThemes.selectedThemeIDtrueundefined
services.sync.prefs.sync.lightweightThemes.usedThemestrueundefined
signon.management.page.enabledundefinedfalse
signon.showAutoCompleteOriginsundefinedfalse
toolkit.content-background-hang-monitor.disabledundefinedfalse
toolkit.legacyUserProfileCustomizations.stylesheetsundefinedfalse
toolkit.telemetry.ecosystemtelemetry.enabledundefinedfalse
ui.android.mouse_as_touchundefined1
ui.use_activity_cursorfalseundefined
urlclassifier.trackingAnnotationTabletest-track-simple,base-track-digest256test-track-simple,ads-track-digest256,social-track-digest256,analytics-track-digest256,content-track-digest256
view_source.tabundefinedtrue
webchannel.allowObject.urlWhitelisthttps://content.cdn.mozilla.net https://input.mozilla.org https://support.mozilla.org https://install.mozilla.orghttps://content.cdn.mozilla.net https://support.mozilla.org https://install.mozilla.org
webgl.bypass-shader-validationfalseundefined
Default pref Javascript files
PrefFirefox 67.0Firefox 68.0 beta 4
browser/omni.ja.d/defaults/preferences/debugger.jspresentpresent
browser/omni.ja.d/defaults/preferences/devtools-client.jspresentpresent
browser/omni.ja.d/defaults/preferences/devtools-startup.jspresentpresent
browser/omni.ja.d/defaults/preferences/firefox-branding.jspresentpresent
browser/omni.ja.d/defaults/preferences/firefox-l10n.jspresentpresent
browser/omni.ja.d/defaults/preferences/firefox.jspresentpresent
browser/omni.ja.d/defaults/preferences/webide.jspresentpresent
omni.ja.d/defaults/pref/marionette.jspresentpresent
omni.ja.d/defaults/pref/remote.jsundefinedpresent
omni.ja.d/defaults/pref/services-sync.jspresentpresent
omni.ja.d/greprefs.jspresentpresent