This is difference between the default preference of Firefox 64.0 beta 4 and one of 62.0.

Preference difference
PrefFirefox 64.0Firefox 65.0 beta 4
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.relative-update.enabledundefinedtrue
browser.contentblocking.control-center.ui.showAllowedLabelsundefinedfalse
browser.contentblocking.control-center.ui.showBlockedLabelsundefinedfalse
browser.contentblocking.cookies-site-data.ui.reject-trackers.enabledtrueundefined
browser.contentblocking.cookies-site-data.ui.reject-trackers.recommendedtrueundefined
browser.contentblocking.fastblock.control-center.ui.enabledfalseundefined
browser.contentblocking.fastblock.ui.enabledfalseundefined
browser.contentblocking.global-toggle.enabledfalseundefined
browser.contentblocking.rejecttrackers.ui.enabledtrueundefined
browser.contentblocking.rejecttrackers.ui.recommendedtrueundefined
browser.contentblocking.reportBreakage.enabledfalsetrue
browser.contentblocking.trackingprotection.ui.enabledtrueundefined
browser.discovery.containers.enabledundefinedtrue
browser.discovery.enabledundefinedtrue
browser.discovery.sitesundefinedaddons.mozilla.org
browser.engagement.recent_visited_origins.expiryundefined86400
browser.fastblock.limit20000undefined
browser.fastblock.timeout5000undefined
browser.fixup.hide_user_passtrueundefined
browser.newtabpage.activity-stream.asrouter.providers.snippets{"id":"snippets","enabled":false,"type":"remote","url":"https://snippets.cdn.mozilla.net/%STARTPAGE_VERSION%/%NAME%/%VERSION%/%APPBUILDID%/%BUILD_TARGET%/%LOCALE%/%CHANNEL%/%OS_VERSION%/%DISTRIBUTION%/%DISTRIBUTION_VERSION%/","updateCycleInMs":14400000}{"id":"snippets","enabled":true,"type":"remote","url":"https://snippets.cdn.mozilla.net/%STARTPAGE_VERSION%/%NAME%/%VERSION%/%APPBUILDID%/%BUILD_TARGET%/%LOCALE%/%CHANNEL%/%OS_VERSION%/%DISTRIBUTION%/%DISTRIBUTION_VERSION%/","updateCycleInMs":14400000}
browser.newtabpage.activity-stream.improvesearch.topSiteSearchShortcutsfalsetrue
browser.safebrowsing.provider.mozilla.listsbase-track-digest256,mozstd-trackwhite-digest256,content-track-digest256,mozplugin-block-digest256,mozplugin2-block-digest256,block-flash-digest256,except-flash-digest256,allow-flashallow-digest256,except-flashallow-digest256,block-flashsubdoc-digest256,except-flashsubdoc-digest256,except-flashinfobar-digest256,ads-track-digest256,social-track-digest256,analytics-track-digest256,fastblock1-track-digest256,fastblock1-trackwhite-digest256,fastblock2-track-digest256,fastblock2-trackwhite-digest256,fastblock3-track-digest256base-track-digest256,mozstd-trackwhite-digest256,content-track-digest256,mozplugin-block-digest256,mozplugin2-block-digest256,block-flash-digest256,except-flash-digest256,allow-flashallow-digest256,except-flashallow-digest256,block-flashsubdoc-digest256,except-flashsubdoc-digest256,except-flashinfobar-digest256,ads-track-digest256,social-track-digest256,analytics-track-digest256
browser.schedulePressure.defaultCount3undefined
browser.schedulePressure.enabledtrueundefined
browser.schedulePressure.timeoutMs300undefined
browser.security.newcerterrorpage.enabledfalsetrue
browser.security.newcerterrorpage.mitm.enabledundefinedtrue
browser.sessionstore.warnOnQuitundefinedfalse
browser.tabs.20FpsThrobberfalseundefined
browser.tabs.30FpsThrobberfalseundefined
browser.urlbar.autocomplete.enabledtrueundefined
browser.urlbar.matchBehavior1undefined
browser.urlbar.suggest.history.onlyTypedfalseundefined
canvas.customfocusring.enabledfalseundefined
devtools.aboutdebugging.networkundefinedfalse
devtools.aboutdebugging.wifiundefinedfalse
devtools.console.stdout.chromeundefinedfalse
devtools.console.stdout.contentundefinedfalse
devtools.debugger.end-panel-sizeundefined300
devtools.debugger.features.event-listenersfalseundefined
devtools.debugger.features.origial-blackboxundefinedfalse
devtools.debugger.features.xhr-breakpointsundefinedtrue
devtools.debugger.forbid-certified-appstrueundefined
devtools.debugger.loggingundefinedfalse
devtools.debugger.new-debugger-frontendtrueundefined
devtools.debugger.start-panel-sizeundefined300
devtools.debugger.xhr-breakpoints-visibleundefinedtrue
devtools.flexboxinspector.enabledfalsetrue
devtools.inspector.changes.enabledfalsetrue
devtools.inspector.flexboxHighlighter.enabledfalsetrue
devtools.inspector.fonteditor.enabledtrueundefined
devtools.inspector.showUserAgentShadowRootsundefinedfalse
devtools.netmonitor.visibleColumns["status","method","file","domain","cause","type","transferred","contentSize","waterfall"]["status","method","domain","file","cause","type","transferred","contentSize","waterfall"]
devtools.performance.profiler.sample-frequency-hzundefined1000
devtools.performance.profiler.sample-frequency-khz1undefined
devtools.recordreplay.allowRepaintFailuresundefinedtrue
devtools.recordreplay.includeSystemScriptsundefinedfalse
devtools.recordreplay.timeline.enabledundefinedfalse
devtools.webconsole.jsterm.reverse-searchfalsetrue
dom.browserElement.maxScreenshotDelayMS2000undefined
dom.ipc.tabs.createKillHardCrashReportsundefinedfalse
dom.keyboardevent.dispatch_during_compositionfalsetrue
dom.keyboardevent.keypress.dispatch_non_printable_keys_only_system_group_in_contentfalsetrue
dom.keyboardevent.keypress.hack.dispatch_non_printable_keysundefined
dom.keyboardevent.keypress.hack.use_legacy_keycode_and_charcodeundefined
dom.payments.request.supportedRegionsundefinedUS,CA
dom.performance.time_to_contentful_paint.enabledundefinedfalse
dom.sidebar.enabledundefinedtrue
dom.storage.next_genundefinedfalse
dom.storage.shadow_writesundefinedtrue
dom.storage.snapshot_prefillundefined16384
dom.storage.snapshot_reusingundefinedtrue
dom.storage_access.auto_grantsundefinedtrue
dom.storage_access.max_concurrent_auto_grantsundefined5
dom.ua_widget.enabledfalsetrue
dom.webcomponents.customelements.enabledtrueundefined
dom.webcomponents.shadowdom.enabledtrueundefined
dom.window.event.enabledfalsetrue
extensions.formautofill.reauth.enabledundefinedfalse
extensions.webcompat-reporter.enabledfalsetrue
geo.provider.use_gpsdfalseundefined
gfx.webrender.debug.slow-frame-indicatorundefinedfalse
gfx.webrender.debug.texture-cache.clear-evictedundefinedtrue
gfx.webrender.picture-cachingundefinedfalse
image.animated.decode-on-demand.recycleundefinedtrue
image.animated.generate-full-framesfalsetrue
image.http.accept*/*image/webp,*/*
image.webp.enabledundefinedtrue
io.activity.intervalMilliseconds0undefined
javascript.options.bigintundefinedfalse
javascript.options.streamsfalsetrue
layout.css.shape-outside.enabledtrueundefined
layout.css.text-align-unsafe-value.enabledfalseundefined
media.av1.use-dav1dundefinedfalse
media.getusermedia.agc31
media.getusermedia.use_aec_mobileundefinedfalse
media.navigator.mediadatadecoder_enabledfalseundefined
media.navigator.mediadatadecoder_h264_enabledfalsetrue
media.navigator.mediadatadecoder_vpx_enabledundefinedfalse
network.IDN.blacklist_chars ¼½¾ǃː̷̸։֊׃״؉؊٪۔܁܂܃܄ᅟᅠ᜵           ​‎‏‐’․‧

‪‫‬‭‮ ‹›⁁⁄⁒ ⅓⅔⅕⅖⅗⅘⅙⅚⅛⅜⅝⅞⅟∕∶⎮╱⧶⧸⫻⫽⿰⿱⿲⿳⿴⿵⿶⿷⿸⿹⿺⿻　。〔〕〳゠ㅤ㈝㈞㎮㎯㏆㏟꞉︔︕︿﹝﹞．／｡ﾠ�undefined
network.IDN.extra_allowed_charsundefined
network.IDN.extra_blocked_charsundefined
network.connectivity-service.DNSv4.domainundefinedmozilla.org
network.connectivity-service.DNSv6.domainundefinedmozilla.org
network.connectivity-service.IPv4.urlundefinedhttp://detectportal.firefox.com/success.txt?ipv4
network.connectivity-service.IPv6.urlundefinedhttp://detectportal.firefox.com/success.txt?ipv6
network.connectivity-service.enabledundefinedtrue
network.cookie.cookieBehaviorundefined4
network.http.accept.defaulttext/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
network.http.spdy.enable-hpack-dumpundefinedfalse
network.http.spdy.websocketsundefinedtrue
network.trr.custom_uriundefined
pdfium.enabledfalseundefined
privacy.popups.maxReportedundefined100
privacy.restrict3rdpartystorage.partitionedHostsundefinedaccounts.google.com/o/oauth2/
privacy.restrict3rdpartystorage.userInteractionRequiredForHostsundefined
privacy.trackingprotection.introCount0undefined
security.strict_security_checks.enabledundefinedfalse
services.sync.engine.bookmarks.validation.enabledundefinedtrue
services.sync.engine.passwords.validation.enabledundefinedtrue
services.sync.prefs.sync.browser.contentblocking.enabledtrueundefined
services.sync.prefs.sync.browser.urlbar.autocomplete.enabledtrueundefined
services.sync.prefs.sync.browser.urlbar.suggest.history.onlyTypedtrueundefined
services.sync.prefs.sync.privacy.fuzzyfox.clockgrainusundefinedfalse
services.sync.prefs.sync.privacy.fuzzyfox.enabledundefinedfalse
urlclassifier.disallow_completionstest-malware-simple,test-harmful-simple,test-phish-simple,test-unwanted-simple,test-track-simple,test-trackwhite-simple,test-block-simple,goog-downloadwhite-digest256,base-track-digest256,mozstd-trackwhite-digest256,content-track-digest256,mozplugin-block-digest256,mozplugin2-block-digest256,block-flash-digest256,except-flash-digest256,allow-flashallow-digest256,except-flashallow-digest256,block-flashsubdoc-digest256,except-flashsubdoc-digest256,except-flashinfobar-digest256,goog-passwordwhite-proto,ads-track-digest256,social-track-digest256,analytics-track-digest256,fastblock1-track-digest256,fastblock1-trackwhite-digest256,fastblock2-track-digest256,fastblock2-trackwhite-digest256,fastblock3-track-digest256test-malware-simple,test-harmful-simple,test-phish-simple,test-unwanted-simple,test-track-simple,test-trackwhite-simple,test-block-simple,goog-downloadwhite-digest256,base-track-digest256,mozstd-trackwhite-digest256,content-track-digest256,mozplugin-block-digest256,mozplugin2-block-digest256,block-flash-digest256,except-flash-digest256,allow-flashallow-digest256,except-flashallow-digest256,block-flashsubdoc-digest256,except-flashsubdoc-digest256,except-flashinfobar-digest256,goog-passwordwhite-proto,ads-track-digest256,social-track-digest256,analytics-track-digest256
urlclassifier.trackingAnnotationSkipURLsundefinedgoogle.com/recaptcha/,*.google.com/recaptcha/
urlclassifier.trackingAnnotationTabletest-track-simple,base-track-digest256test-track-simple,base-track-digest256,content-track-digest256
Default pref Javascript files
PrefFirefox 64.0Firefox 65.0 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/services-sync.jspresentpresent
omni.ja.d/greprefs.jspresentpresent