This is difference between the default preference of Firefox 57.0 beta 3 and one of 56.0.

Preference difference
PrefFirefox 56.0Firefox 57.0 beta 3
accessibility.indicator.enabledundefinedtrue
accessibility.loadedInLastSessionfalseundefined
accessibility.support.urlundefinedhttps://support.mozilla.org/%LOCALE%/kb/accessibility-services
app.support.e10sAccessibilityUrlhttps://support.mozilla.org/1/firefox/%VERSION%/%OS%/%LOCALE%/accessibility-pptundefined
app.update.staging.enabledtruefalse
apz.autoscroll.enabledfalsetrue
apz.drag.touch.enabledundefinedtrue
apz.frame_delay.enabledfalsetrue
apz.keyboard.enabledfalsetrue
apz.keyboard.passive-listenersundefinedtrue
browser.bookmarks.openInTabClosesMenuundefinedtrue
browser.bookmarks.showRecentlyBookmarkedtrueundefined
browser.cache.auto_delete_cache_version0undefined
browser.cache.use_new_backend0undefined
browser.cache.use_new_backend_temptrueundefined
browser.casting.enabledfalseundefined
browser.crashReports.unsubmittedCheck.enabledfalsetrue
browser.customizemode.tip0.learnMoreUrlhttps://support.mozilla.org/1/firefox/%VERSION%/%OS%/%LOCALE%/customizeundefined
browser.customizemode.tip0.shownfalseundefined
browser.download.autohideButtonundefinedtrue
browser.gesture.pinch.incmd_fullZoomReduce
browser.gesture.pinch.in.shiftcmd_fullZoomReset
browser.gesture.pinch.outcmd_fullZoomEnlarge
browser.gesture.pinch.out.shiftcmd_fullZoomReset
browser.library.activity-stream.enabledundefinedtrue
browser.newtabpage.activity-stream.aboutHome.enabledundefinedtrue
browser.newtabpage.activity-stream.enabledfalsetrue
browser.newtabpage.activity-stream.prerenderundefinedtrue
browser.onboarding.hiddenfalseundefined
browser.onboarding.newtourprivate,addons,customize,search,default,syncperformance,private,screenshots,addons,customize,default
browser.onboarding.notification.max-life-time-all-tours-msundefined1209600000
browser.onboarding.stateundefineddefault
browser.onboarding.tourset-version12
browser.onboarding.updatetourperformance,library,screenshots,singlesearch,customize,sync
browser.photon.structure.enabledfalseundefined
browser.ping-centre.logundefinedfalse
browser.ping-centre.production.endpointundefinedhttps://tiles.services.mozilla.com/v3/links/ping-centre
browser.ping-centre.staging.endpointundefinedhttps://onyx_tiles.stage.mozaws.net/v3/links/ping-centre
browser.ping-centre.telemetryundefinedtrue
browser.preferences.offlineGroup.enabledtruefalse
browser.preferences.useOldOrganizationfalseundefined
browser.safebrowsing.passwords.enabledundefinedfalse
browser.safebrowsing.provider.google.advisoryNameGoogle Safe Browsing.Google Safe Browsing
browser.safebrowsing.provider.google4.advisoryNameGoogle Safe Browsing.Google Safe Browsing
browser.safebrowsing.provider.google4.listsgoog-badbinurl-proto,goog-downloadwhite-proto,goog-phish-proto,googpub-phish-proto,goog-malware-proto,goog-unwanted-protogoog-badbinurl-proto,goog-downloadwhite-proto,goog-phish-proto,googpub-phish-proto,goog-malware-proto,goog-unwanted-proto,goog-harmful-proto,goog-passwordwhite-proto
browser.search.widget.inNavBartruefalse
browser.slowStartup.timeThreshold3000020000
browser.storageManager.enabledfalsetrue
browser.tabs.extraDragSpaceundefinedfalse
browser.tabs.loadBookmarksInTabsundefinedfalse
browser.tabs.remote.warmup.enabledundefinedfalse
browser.tabs.remote.warmup.maxTabsundefined3
browser.tabs.remote.warmup.unloadDelayMsundefined2000
browser.touchmode.autofalsetrue
browser.urlbar.maxHistoricalSearchSuggestionsundefined1
browser.urlbar.speculativeConnect.enabledfalsetrue
devtools.debugger.chrome-debugging-port6080undefined
devtools.debugger.features.async-steppingundefinedtrue
devtools.debugger.features.wasmundefinedtrue
devtools.debugger.project-text-search-enabledundefinedtrue
devtools.devedition.promo.enabledfalsetrue
devtools.enabledundefinedtrue
devtools.hud.loglimit100010000
devtools.loader.hotreloadfalseundefined
devtools.netmonitor.persistlogundefinedfalse
devtools.styleeditor.source-maps-enabledtrueundefined
devtools.webconsole.new-frontend-enabledfalsetrue
devtools.webide.adaptersAddonIDfxdevtools-adapters@mozilla.orgundefined
devtools.webide.adaptersAddonURLhttps://ftp.mozilla.org/pub/mozilla.org/labs/valence/#OS#/valence-#OS#-latest.xpiundefined
devtools.webide.autoinstallFxdtAdapterstrueundefined
dom.abortController.enabledundefinedtrue
dom.abortController.fetch.enabledundefinedtrue
dom.enable_performance_observerfalsetrue
dom.event.coalesce_mouse_moveundefinedfalse
dom.forms.datetimefalsetrue
dom.ipc.schedulerundefinedfalse
dom.ipc.scheduler.chaoticSchedulingundefinedfalse
dom.ipc.scheduler.preemptionundefinedfalse
dom.ipc.scheduler.threadCountundefined2
dom.ipc.scheduler.useMultipleQueuesundefinedtrue
dom.ipc.useNativeEventProcessing.contentundefinedtrue
dom.max_ext_content_script_run_timeundefined5
dom.payments.loglevelundefinedWarn
dom.storageManager.enabledfalsetrue
dom.streams.enabledundefinedfalse
editor.use_div_for_default_newlinesfalsetrue
extensions.formautofill.availablestaged-rolloutdetect
extensions.formautofill.creditCards.availableundefinedfalse
extensions.legacy.enabledtruefalse
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.webrender.blob-imagesundefinedfalse
gfx.webrender.debug.profilerundefinedfalse
gfx.webrender.debug.render-targetsundefinedfalse
gfx.webrender.debug.texture-cacheundefinedfalse
gfx.webrender.profiler.enabledfalseundefined
image.cache.factor2.threshold-surfacesundefined4
input_event_queue.count_for_predictionundefined9
input_event_queue.default_duration_per_eventundefined1
input_event_queue.duration.maxundefined8
input_event_queue.duration.minundefined1
input_event_queue.supportedundefinedtrue
javascript.options.mem.gc_allocation_threshold_factorundefined90
javascript.options.mem.gc_allocation_threshold_factor_avoid_interruptundefined90
javascript.options.mem.nursery.max_kb-116384
javascript.options.wasm_ionjitundefinedtrue
jsloader.shareGlobalundefinedtrue
layers.omtp.enabledundefinedfalse
layers.omtp.force-syncundefinedfalse
layout.css.clip-path-shapes.enabledtrueundefined
layout.css.ruby.intercharacter.enabledundefinedfalse
layout.css.servo.enabledfalsetrue
media.eme.chromium-api.enabledtrueundefined
media.navigator.streams.fakeundefinedfalse
media.wakelock_timeout2000undefined
memory.free_dirty_pagesfalsetrue
middlemouse.contentLoadURLtruefalse
network.cookie.ipc.syncundefinedfalse
network.http.keep_empty_response_headers_as_empty_stringtrueundefined
network.http.rcwn.min_wait_before_racing_msundefined0
network.http.tailing.delay-maxundefined6000
network.http.tailing.delay-quantumundefined600
network.http.tailing.delay-quantum-after-domcontentloadedundefined100
network.http.tailing.enabledundefinedtrue
network.standard-url.punycode-hostfalsetrue
plugin.state.flash21
preferences.allow.omt-writefalsetrue
privacy.popups.disable_from_plugins23
privacy.userContext.extensionundefined
security.data_uri.block_toplevel_data_uri_navigationsfalsetrue
security.data_uri.unique_opaque_originfalsetrue
security.mixed_content.send_hsts_primingfalsetrue
security.mixed_content.use_hstsfalsetrue
security.sandbox.content.level23
security.tls.version.max34
security.use_sqldbundefinedfalse
security.webauth.u2f_enable_softtokenfalseundefined
security.webauth.u2f_enable_usbtokenfalseundefined
security.webauth.webauthn_enable_usbtokenfalsetrue
services.sync.engine.bookmarks.validation.enabledundefinedtrue
services.sync.prefs.sync.browser.safebrowsing.downloads.enabledundefinedtrue
services.sync.prefs.sync.browser.safebrowsing.passwords.enabledundefinedtrue
social.share.activationPanelEnabledtrueundefined
social.shareDirectoryhttps://activations.cdn.mozilla.net/sharePanel.htmlundefined
toolkit.telemetry.bhrPing.enabledundefinedtrue
toolkit.telemetry.firstShutdownPing.enabledundefinedtrue
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-digest256,block-flash-digest256,except-flash-digest256,allow-flashallow-digest256,except-flashallow-digest256,block-flashsubdoc-digest256,except-flashsubdoc-digest256,except-flashinfobar-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
urlclassifier.downloadAllowTablegoog-downloadwhite-digest256goog-downloadwhite-proto
urlclassifier.downloadBlockTablegoog-badbinurl-shavargoog-badbinurl-proto
urlclassifier.malwareTablegoog-malware-shavar,goog-unwanted-shavar,test-malware-simple,test-unwanted-simplegoog-malware-proto,goog-unwanted-proto,test-harmful-simple,test-malware-simple,test-unwanted-simple
urlclassifier.passwordAllowTableundefinedgoog-passwordwhite-proto
urlclassifier.phishTablegoog-phish-shavar,test-phish-simplegoog-phish-proto,test-phish-simple
webgl.1.allow-core-profilesundefinedfalse
Default pref Javascript files
PrefFirefox 56.0Firefox 57.0 beta 3
browser/omni.ja.d/defaults/preferences/debugger.jspresentpresent
browser/omni.ja.d/defaults/preferences/devtools-startup-prefs.jsundefinedpresent
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/marionette.jspresentpresent
omni.ja.d/defaults/pref/services-sync.jspresentpresent
omni.ja.d/greprefs.jspresentpresent