This is difference between the default preference of Firefox 53.0 beta 6 and one of 52.0.1.

Preference difference
PrefFirefox 52.0.1Firefox 53.0 beta 6
accessibility.ipc_architecture.enabledtrueundefined
browser.addon-watch.ignore["mochikit@mozilla.org","special-powers@mozilla.org","fxdevtools-adapters@mozilla.org","fx-devtools"]["mochikit@mozilla.org","special-powers@mozilla.org","fxdevtools-adapters@mozilla.org","fx-devtools","webcompat-reporter@mozilla.org"]
browser.crashReports.unsubmittedCheck.enabledfalsetrue
browser.formautofill.experimentalundefinedfalse
browser.migrate.automigrate.enabledfalsetrue
browser.migrate.automigrate.undo-surveyundefinedhttps://qsurvey.mozilla.com/s3/Firefox-52-Import-Undo?prevBrowser=%IMPORTEDBROWSER%
browser.migrate.automigrate.undo-survey-localesundefineden-US
browser.migrate.chrome.history.limit02000
browser.migrate.chrome.history.maxAgeInDays0180
browser.preferences.animateFadeInfalseundefined
browser.safebrowsing.provider.google4.gethashURLhttps://safebrowsing.googleapis.com/v4/fullHashes:find?$req=%REQUEST_BASE64%&$ct=application/x-protobuf&key=%GOOGLE_API_KEY%
browser.safebrowsing.provider.mozilla.listsbase-track-digest256,mozstd-trackwhite-digest256,content-track-digest256,mozplugin-block-digest256,mozplugin2-block-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
browser.safebrowsing.temporary.take_v4_completion_resultundefinedfalse
browser.storageManager.enabledundefinedfalse
browser.tabs.dontfocusfordialogstrueundefined
browser.tabs.remote.separateFileUriProcessundefinedfalse
browser.uitour.readerViewTrigger^https:\/\/www\.mozilla\.org\/[^\/]+\/firefox\/reading\/startundefined
browser.urlbar.decodeURLsOnCopyundefinedfalse
devtools.apps.forbidden-permissionsembed-appsundefined
devtools.command-button-pick.enabledundefinedtrue
devtools.debugger.call-stack-visibleundefinedfalse
devtools.debugger.end-panel-collapsedundefinedfalse
devtools.debugger.pending-selected-locationundefined{}
devtools.debugger.scopes-visibleundefinedfalse
devtools.debugger.start-panel-collapsedundefinedfalse
devtools.debugger.tabsundefined[]
devtools.devedition.promo.enabledfalsetrue
devtools.gridinspector.showGridLineNumbersundefinedfalse
devtools.gridinspector.showInfiniteLinesundefinedfalse
devtools.inspector.colorWidget.enabledundefinedfalse
devtools.jsonview.enabledfalsetrue
devtools.netmonitor.har.defaultFileNameArchive %y-%m-%d %H-%M-%SArchive %date
devtools.netmonitor.statisticstrueundefined
devtools.screenshot.audio.enabledundefinedtrue
devtools.screenshot.clipboard.enabledundefinedfalse
devtools.toolbox.toolbarSpec["splitconsole", "paintflashing toggle","scratchpad","resize toggle","screenshot --fullpage", "rulers", "measure"]["splitconsole", "paintflashing toggle","scratchpad","resize toggle","screenshot --fullpage --file", "rulers", "measure"]
devtools.webconsole.filter.cssundefinedfalse
dom.IntersectionObserver.enabledundefinedfalse
dom.beforeAfterKeyboardEvent.enabledfalseundefined
dom.details_element.enabledtrueundefined
dom.dialog_element.enabledundefinedfalse
dom.forms.selectSearchundefinedfalse
dom.ipc.processCount.webLargeAllocationundefined10
dom.largeAllocationHeader.enabledundefinedtrue
dom.mozInputMethod.enabledfalseundefined
dom.mozNetworkStats.enabledfalseundefined
dom.mozPermissionSettings.enabledfalseundefined
dom.mozSettings.SettingsDB.debug.enabledfalseundefined
dom.mozSettings.SettingsDB.verbose.enabledfalseundefined
dom.mozSettings.SettingsManager.debug.enabledfalseundefined
dom.mozSettings.SettingsManager.verbose.enabledfalseundefined
dom.mozSettings.SettingsRequestManager.debug.enabledfalseundefined
dom.mozSettings.SettingsRequestManager.verbose.enabledfalseundefined
dom.mozSettings.SettingsService.debug.enabledfalseundefined
dom.mozSettings.SettingsService.verbose.enabledfalseundefined
dom.mozSettings.allowForceReadOnlyfalseundefined
dom.mozSettings.enabledfalseundefined
dom.node.rootNode.enabledfalseundefined
dom.presentation.discovery.legacy.enabledfalseundefined
dom.select_popup_in_parent.enabledundefinedfalse
dom.storage.testingundefinedfalse
dom.system_update.debugfalseundefined
dom.system_update.enabledfalseundefined
extensions.getAddons.themes.browseURLundefinedhttps://addons.mozilla.org/%LOCALE%/firefox/themes/?src=firefox
extensions.webcompat-reporter.enabledundefinedfalse
extensions.webcompat-reporter.newIssueEndpointundefinedhttps://webcompat.com/issues/new
extensions.webextensions.identity.redirectDomainundefinedextensions.allizom.org
extensions.webextensions.remoteundefinedfalse
extensions.webextensions.themes.enabledundefinedfalse
font.name-list.serif.x-mathLatin Modern Math, XITS Math, Cambria Math, Libertinus Math, DejaVu Math TeX Gyre, TeX Gyre Bonum Math, TeX Gyre Pagella Math, TeX Gyre Schola, TeX Gyre Termes Math, STIX Math, Asana Math, STIXGeneral, DejaVu Serif, DejaVu Sans, serifLatin Modern Math, STIX Two Math, XITS Math, Cambria Math, Libertinus Math, DejaVu Math TeX Gyre, TeX Gyre Bonum Math, TeX Gyre Pagella Math, TeX Gyre Schola, TeX Gyre Termes Math, STIX Math, Asana Math, STIXGeneral, DejaVu Serif, DejaVu Sans, serif
gecko.handlerService.allowRegisterFromDifferentHostfalseundefined
gfx.content.use-native-pushlayertrueundefined
gfx.prefer-mesa-llvmpipefalseundefined
identity.fxaccounts.settings.devices.uriundefinedhttps://accounts.firefox.com/settings/clients?service=sync&context=fx_desktop_v3
image.mozsamplesize.enabledfalseundefined
javascript.options.shared_memoryfalsetrue
layers.geometry.basic.enabledundefinedtrue
layers.geometry.opengl.enabledundefinedtrue
layout.animation.prerender.absolute-limit-xundefined4096
layout.animation.prerender.absolute-limit-yundefined4096
layout.animation.prerender.partialundefinedfalse
layout.animation.prerender.viewport-ratio-limit-xundefined1.125
layout.animation.prerender.viewport-ratio-limit-yundefined1.125
layout.css.display-contents.enabledtrueundefined
layout.css.display-flow-root.enabledundefinedtrue
layout.css.font-variations.enabledundefinedfalse
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","footerURL":"resource:///chrome/browser/content/browser/defaultthemes/1.footer.jpg","textcolor":"#000000","accentcolor":"#f2d9b1","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","footerURL":"resource:///chrome/browser/content/browser/defaultthemes/2.footer.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-3","homepageURL":"https://addons.mozilla.org/firefox/addon/linen-light/","headerURL":"resource:///chrome/browser/content/browser/defaultthemes/3.header.png","footerURL":"resource:///chrome/browser/content/browser/defaultthemes/3.footer.png","accentcolor":"#ada8a8","iconURL":"resource:///chrome/browser/content/browser/defaultthemes/3.icon.png","previewURL":"resource:///chrome/browser/content/browser/defaultthemes/3.preview.png","author":"DVemer","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","footerURL":"resource:///chrome/browser/content/browser/defaultthemes/4.footer.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"},{"id":"recommended-5","homepageURL":"https://addons.mozilla.org/firefox/addon/carbon-light/","headerURL":"resource:///chrome/browser/content/browser/defaultthemes/5.header.png","footerURL":"resource:///chrome/browser/content/browser/defaultthemes/5.footer.png","textcolor":"#3b3b3b","accentcolor":"#2e2e2e","iconURL":"resource:///chrome/browser/content/browser/defaultthemes/5.icon.jpg","previewURL":"resource:///chrome/browser/content/browser/defaultthemes/5.preview.jpg","author":"Jaxivo","version":"1.0"}][{"id":"recommended-1","homepageURL":"https://addons.mozilla.org/firefox/addon/a-web-browser-renaissance/","headerURL":"resource:///chrome/browser/content/browser/defaultthemes/1.header.jpg","footerURL":"resource:///chrome/browser/content/browser/defaultthemes/1.footer.jpg","textcolor":"#000000","accentcolor":"#f2d9b1","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","footerURL":"resource:///chrome/browser/content/browser/defaultthemes/2.footer.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","footerURL":"resource:///chrome/browser/content/browser/defaultthemes/4.footer.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"}]
media.cubeb.log_levelundefined
media.decoder-doctor.notifications-allowedMediaWMFNeeded,MediaWidevineNoWMFNoSilverlight,MediaCannotInitializePulseAudio,MediaCannotPlayNoDecoders,MediaUnsupportedLibavcodecMediaWMFNeeded,MediaWidevineNoWMF,MediaCannotInitializePulseAudio,MediaCannotPlayNoDecoders,MediaUnsupportedLibavcodec
media.decoder.recycle.enabledundefinedfalse
media.dormant-on-pause-timeout-ms-15000
media.getusermedia.browser.enabledtruefalse
media.getusermedia.screensharing.allow_on_old_platformsfalseundefined
media.gmp.decoder.aac20
media.gmp.decoder.h26420
network.http.referer.userControlPolicyundefined3
network.standard-url.enable-rustundefinedfalse
network.standard-url.encode-utf8trueundefined
network.standard-url.escape-utf8trueundefined
places.frecency.permRedirectVisitBonus050
places.frecency.redirectSourceVisitBonusundefined25
places.frecency.tempRedirectVisitBonus040
plugins.flashBlock.enabledundefinedfalse
print.print_via_parentfalsetrue
privacy.history.customundefinedfalse
privacy.permissionPrompts.showCloseButtonundefinedfalse
privacy.temporary_permission_expire_time_msundefined3600000
privacy.trackingprotection.annotate_channelsundefinedfalse
privacy.trackingprotection.lower_network_priorityundefinedfalse
privacy.userContext.longPressBehaviorundefined0
security.mixed_content.hsts_priming_request_timeoutundefined3000
security.ssl.enable_npntrueundefined
security.ssl.false_start.require-npnfalseundefined
security.tls.unrestricted_rc4_fallbackfalseundefined
security.tls.version.max34
security.webauth.webauthnundefinedfalse
security.webauth.webauthn_enable_softtokenundefinedfalse
security.webauth.webauthn_enable_usbtokenundefinedfalse
services.blocklist.pinning.bucketundefinedpinning
services.blocklist.pinning.checkedundefined0
services.blocklist.pinning.collectionundefinedpins
services.blocklist.pinning.enabledundefinedtrue
services.sync.engine.tabs.filteredUrls^(about:.*|chrome://weave/.*|wyciwyg:.*|file:.*|blob:.*)$^(about:.*|resource:.*|chrome:.*|wyciwyg:.*|file:.*|blob:.*)$
svg.disabledundefinedfalse
urlclassifier.disallow_completionstest-malware-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-digest256test-malware-simple,test-phish-simple,test-unwanted-simple,test-track-simple,test-trackwhite-simple,test-block-simple,test-flashallow-simple,testexcept-flashallow-simple,test-flash-simple,testexcept-flash-simple,test-flashsubdoc-simple,testexcept-flashsubdoc-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
urlclassifier.flashAllowExceptTableundefinedtestexcept-flashallow-simple,except-flashallow-digest256
urlclassifier.flashAllowTableundefinedtest-flashallow-simple,allow-flashallow-digest256
urlclassifier.flashExceptTableundefinedtestexcept-flash-simple,except-flash-digest256
urlclassifier.flashSubDocExceptTableundefinedtestexcept-flashsubdoc-simple,except-flashsubdoc-digest256
urlclassifier.flashSubDocTableundefinedtest-flashsubdoc-simple,block-flashsubdoc-digest256
urlclassifier.flashTableundefinedtest-flash-simple,block-flash-digest256
webextensions.storage.sync.enabledfalsetrue
webgl.enable-debug-renderer-infofalsetrue
webgl.max-acceptable-fb-status-invalsundefined0
webgl.max-perf-warningsundefined0
Default pref Javascript files
PrefFirefox 52.0.1Firefox 53.0 beta 6
browser/omni.ja.d/defaults/preferences/devtools.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-prefs.jspresentpresent
omni.ja.d/defaults/pref/services-sync.jspresentpresent
omni.ja.d/greprefs.jspresentpresent