This is difference between the default preference of Firefox 63.0 beta 6 and one of 61.0.1.

Preference difference
PrefFirefox 63.0Firefox 64.0 beta 6
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
browser.audioFeeds.handleraskundefined
browser.contentblocking.reportBreakage.enabledfalsetrue
browser.fastblock.limit020000
browser.feeds.handleraskundefined
browser.fission.simulateundefinedfalse
browser.migrate.automigrate.daysToOfferUndo4undefined
browser.migrate.automigrate.enabledfalseundefined
browser.migrate.automigrate.inpage.ui.enabledfalseundefined
browser.migrate.automigrate.ui.enabledtrueundefined
browser.newtabpage.activity-stream.improvesearch.topSiteSearchShortcutsfalsetrue
browser.onboarding.enabledtrueundefined
browser.onboarding.newtourperformance,private,screenshots,addons,customize,defaultundefined
browser.onboarding.notification.finishedfalseundefined
browser.onboarding.notification.max-life-time-all-tours-ms1209600000undefined
browser.onboarding.notification.max-life-time-per-tour-ms432000000undefined
browser.onboarding.notification.max-prompt-count-per-tour8undefined
browser.onboarding.notification.mute-duration-on-first-session-ms300000undefined
browser.onboarding.statedefaultundefined
browser.onboarding.tourset-version2undefined
browser.onboarding.updatetourperformance,library,screenshots,singlesearch,customize,syncundefined
browser.safebrowsing.downloads.remote.timeout_ms1000015000
browser.tabs.multiselectfalsetrue
browser.urlbar.ctrlCanonizesURLsundefinedtrue
browser.urlbar.quantumbarundefinedfalse
browser.videoFeeds.handleraskundefined
canvas.imagebitmap_extensions.enabledfalseundefined
devtools.commands.dirundefined
devtools.debugger.features.map-await-expressionfalsetrue
devtools.debugger.features.replayfalseundefined
devtools.gcli.eagerHelper2undefined
devtools.gcli.hideIntrofalseundefined
devtools.gcli.imgurClientID0df414e888d7240undefined
devtools.gcli.imgurUploadURLhttps://api.imgur.com/3/imageundefined
devtools.gcli.jquerySrchttps://cdnjs.cloudflare.com/ajax/libs/jquery/2.2.1/jquery.min.jsundefined
devtools.gcli.lodashSrchttps://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.6.1/lodash.min.jsundefined
devtools.gcli.underscoreSrchttps://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.jsundefined
devtools.gridinspector.maxHighlightersundefined3
devtools.inspector.activeSidebarruleviewlayoutview
devtools.inspector.changes.enabledundefinedfalse
devtools.inspector.show-three-pane-tooltiptrueundefined
devtools.inspector.three-pane-first-runtrueundefined
devtools.new-animationinspector.enabledtrueundefined
devtools.performance.recording.ui-base-urlundefinedhttps://perf-html.io
devtools.promote.accessibility1undefined
devtools.recordreplay.mvp.enabledundefinedfalse
devtools.remote.adb.extensionURLundefinedhttps://ftp.mozilla.org/pub/mozilla.org/labs/devtools/adb-extension/#OS#/adb-extension-latest-#OS#.xpi
devtools.responsive.showUserAgentInputundefinedfalse
devtools.responsive.touchSimulation.enabledundefinedfalse
devtools.responsive.userAgentundefined
devtools.responsive.viewport.heightundefined480
devtools.responsive.viewport.pixelRatioundefined0
devtools.responsive.viewport.widthundefined320
devtools.webconsole.inputHistoryCount50300
devtools.webconsole.jsterm.codeMirrorfalsetrue
devtools.webconsole.jsterm.reverse-searchundefinedfalse
devtools.webide.adbAddonIDadbhelper@mozilla.orgundefined
devtools.webide.adbAddonURLhttps://ftp.mozilla.org/pub/mozilla.org/labs/fxos-simulator/adb-helper/#OS#/adbhelper-#OS#-latest.xpiundefined
devtools.webide.autoinstallADBExtensionundefinedtrue
devtools.webide.autoinstallADBHelpertrueundefined
dom.caches.enabledtrueundefined
dom.enable_performance_observertrueundefined
dom.indexedDB.storageOption.enabledfalseundefined
dom.keyboardevent.dispatch_during_compositionfalsetrue
dom.netinfo.enabledfalseundefined
dom.payments.request.enabledfalseundefined
dom.performance.enable_scheduler_timingfalsetrue
dom.performance.enable_user_timing_loggingfalseundefined
dom.performance.time_to_first_interactive.enabledundefinedfalse
dom.promise_rejection_events.enabledfalseundefined
dom.storageManager.enabledtrueundefined
dom.streams.enabledfalseundefined
dom.vr.external.notdetected.timeoutundefined60000
dom.vr.external.quit.timeoutundefined10000
dom.vr.service.enabledfalsetrue
dom.webkitBlink.dirPicker.enabledtrueundefined
dom.webnotifications.enabledtrueundefined
dom.webnotifications.requireinteraction.enabledfalseundefined
dom.webnotifications.serviceworker.enabledtrueundefined
dom.xhr.lowercase_header.enabledfalsetrue
editor.inline_table_editing.enabled_by_defaulttruefalse
editor.positioning.enabled_by_defaulttruefalse
editor.resizing.enabled_by_defaulttruefalse
extensions.geckoProfiler.acceptedExtensionIdsgeckoprofiler@mozilla.com,quantum-foxfooding@mozilla.comgeckoprofiler@mozilla.com,quantum-foxfooding@mozilla.com,raptor@mozilla.org
extensions.getAddons.themes.browseURLhttps://addons.mozilla.org/%LOCALE%/firefox/themes/?src=firefoxundefined
extensions.webextensions.enablePerformanceCountersfalsetrue
extensions.webextensions.performanceCountersMaxAgeundefined1000
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,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.com,testpilot.firefox.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,input.mozilla.org,install.mozilla.org,oauth.accounts.firefox.com,profile.accounts.firefox.com,support.mozilla.org,sync.services.mozilla.com,testpilot.firefox.com
extensions.webextensions.userScripts.enabledundefinedfalse
geo.provider.use_gpsdfalseundefined
geo.wifi.urihttps://www.googleapis.com/geolocation/v1/geolocate?key=%GOOGLE_API_KEY%https://location.services.mozilla.com/v1/geolocate?key=%MOZILLA_API_KEY%
gfx.font_ahem_antialias_noneundefinedfalse
gfx.offscreencanvas.enabledfalseundefined
gfx.webrender.blob.paint-flashingundefinedfalse
identity.fxaccounts.commands.enabledfalsetrue
identity.fxaccounts.commands.missed.fetch_intervalundefined86400
image.animated.generate-full-framesundefinedfalse
image.cache.max-rasterized-svg-threshold-kbundefined92160
image.mem.debug-reportingundefinedfalse
javascript.options.baselinejit.thresholdundefined10
javascript.options.ion.frequent_bailout_thresholdundefined10
javascript.options.ion.thresholdundefined1000
layout.accessiblecaret.allow_dragging_across_other_carettrueundefined
layout.accessiblecaret.always_tiltfalseundefined
layout.accessiblecaret.caret_shown_when_long_tapping_on_empty_contentfalseundefined
layout.accessiblecaret.enabledfalseundefined
layout.accessiblecaret.enabled_on_touchtrueundefined
layout.accessiblecaret.extend_selection_for_phone_numberfalseundefined
layout.accessiblecaret.hapticfeedbackfalseundefined
layout.accessiblecaret.height36.0undefined
layout.accessiblecaret.hide_carets_for_mouse_inputtrueundefined
layout.accessiblecaret.margin-left-18.5undefined
layout.accessiblecaret.script_change_update_mode0undefined
layout.accessiblecaret.use_long_tap_injectorfalseundefined
layout.accessiblecaret.width34.0undefined
layout.css.filters.enabledtrueundefined
layout.css.scrollbar-color.enabledundefinedtrue
layout.css.scrollbar-colors.enabledfalseundefined
layout.css.scrollbar-width.enabledfalsetrue
media.getusermedia.agc_enabledfalsetrue
media.navigator.mediadatadecoder_enabledundefinedfalse
media.navigator.mediadatadecoder_h264_enabledundefinedfalse
network.cookie.cookieBehaviorundefined4
network.cookie.ipc.syncfalseundefined
network.http.throttle.enabletruefalse
network.security.esni.enabledundefinedfalse
plugins.remember_infobar_dismissaltrueundefined
privacy.resistFingerprintingfalseundefined
security.certerrors.recordEventTelemetryundefinedtrue
security.identitypopup.recordEventElemetryundefinedtrue
security.pki.distrust_ca_policy12
security.sandbox.plugin.tempDirSuffixundefined
security.tls.hello_downgrade_checkundefinedfalse
services.sync.engine.bookmarks.validation.enabledundefinedtrue
services.sync.engine.passwords.validation.enabledundefinedtrue
toolkit.coverage.enabledundefinedfalse
toolkit.coverage.endpoint.baseundefinedhttps://coverage.mozilla.org
urlclassifier.trackingAnnotationTabletest-track-simple,base-track-digest256test-track-simple,base-track-digest256,content-track-digest256
xpinstall.customConfirmationUItrueundefined
Default pref Javascript files
PrefFirefox 63.0Firefox 64.0 beta 6
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/services-sync.jspresentpresent
omni.ja.d/greprefs.jspresentpresent