This article shows the difference between the default preferences of Firefox 159.0 beta 3 and Firefox 158.0. The diff table below is generated using my small script firefox-prefjs-surveyer.

Preference difference
PrefFirefox 158.0Firefox 159.0 beta 3
app.normandy.api_url https://normandy.cdn.mozilla.net/api/v1
app.releaseNotesURL https://www.firefox.com/%LOCALE%/firefox/%VERSION%/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-desktop&utm_campaign=whatsnew https://www.firefox.com/%LOCALE%/firefox/%VERSION%beta/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-desktop&utm_campaign=whatsnew
app.releaseNotesURL.aboutDialog https://www.firefox.com/%LOCALE%/firefox/%VERSION%/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-desktop&utm_campaign=about-dialog https://www.firefox.com/%LOCALE%/firefox/%VERSION%beta/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-desktop&utm_campaign=about-dialog
app.update.channel release beta
app.update.disabledForTesting undefined true
app.update.url.details https://www.mozilla.org/%LOCALE%/firefox/notes https://www.mozilla.org/%LOCALE%/firefox/beta/notes
app.update.url.manual https://www.mozilla.org/%LOCALE%/firefox/new?reason=manual-update https://www.mozilla.org/%LOCALE%/firefox/beta?reason=manual-update
apz.axis_lock.mode 2 0
apz.content_response_timeout 400 60000
apz.touch_move_tolerance 0.1 0.0
apz.touch_start_tolerance 0.1 0.0
browser.backup.enabled true false
browser.contentblocking.introCount undefined 99
browser.discovery.enabled true false
browser.dom.window.dump.enabled false true
browser.download.alwaysOpenPanel true false
browser.download.panel.shown false true
browser.http.blank_page_with_error_response.enabled false true
browser.load-xul-position.enabled undefined false
browser.mini-window.toolbar.edge-zone-px undefined 12
browser.mini-window.toolbar.hide-delay-ms undefined 2000
browser.mini-window.toolbar.hover-reveal-delay-ms undefined 50
browser.ml.enable true false
browser.ml.hwinference.browser_idle_shutdown_grace_ms undefined 120000
browser.ml.llama.hwInference undefined true
browser.newtabpage.activity-stream.asrouter.userprefs.cfr.features true false
browser.newtabpage.activity-stream.discoverystream.optIn-region-weather-config DE,GB,FR,ES,IT,CH,AT,BE,IE,NL,PL,CZ,SE,SG,HU,SK,FI,DK,NO,PT undefined
browser.newtabpage.activity-stream.discoverystream.rec.impressions {} undefined
browser.newtabpage.activity-stream.feeds.sportsfeed false undefined
browser.newtabpage.activity-stream.hideTopSitesTitle false undefined
browser.newtabpage.activity-stream.pageLayouts.spacesOrder undefined
browser.newtabpage.activity-stream.pageLayouts.widgetFirstContentSlot.widget undefined
browser.newtabpage.activity-stream.privacyInfo.url https://support.mozilla.org/1/firefox/158.0/Linux/en-US/sponsor-privacy https://support.mozilla.org/1/firefox/159.0/Linux/en-US/sponsor-privacy
browser.newtabpage.activity-stream.sectionsLearnMore.url https://support.mozilla.org/1/firefox/158.0/Linux/en-US/firefox-new-tab-personalization https://support.mozilla.org/1/firefox/159.0/Linux/en-US/firefox-new-tab-personalization
browser.newtabpage.activity-stream.showSponsoredTopSites true false
browser.newtabpage.activity-stream.sports.worldCup.liveEndpoint https://merino.services.mozilla.com/api/v1/wcs/live undefined
browser.newtabpage.activity-stream.sports.worldCup.matchesEndpoint https://merino.services.mozilla.com/api/v1/wcs/matches undefined
browser.newtabpage.activity-stream.sports.worldCup.teamsEndpoint https://merino.services.mozilla.com/api/v1/wcs/teams undefined
browser.newtabpage.activity-stream.sports.worldCup.watchLiveEndpoint https://merino.services.mozilla.com/api/v1/wcs/watch-links undefined
browser.newtabpage.activity-stream.support.url https://support.mozilla.org/1/firefox/158.0/Linux/en-US/new-tab https://support.mozilla.org/1/firefox/159.0/Linux/en-US/new-tab
browser.newtabpage.activity-stream.telemetry.structuredIngestion.endpoint https://incoming.telemetry.mozilla.org/submit undefined
browser.newtabpage.activity-stream.testing.shouldInitializeFeeds undefined false
browser.newtabpage.activity-stream.topSitesGroupedPins false true
browser.newtabpage.activity-stream.widgets.clocks.enabled true false
browser.newtabpage.activity-stream.widgets.clocks.region-block undefined DE,FR,PL,US
browser.newtabpage.activity-stream.widgets.crossword.enabled true false
browser.newtabpage.activity-stream.widgets.enabled true false
browser.newtabpage.activity-stream.widgets.focusTimer.enabled true false
browser.newtabpage.activity-stream.widgets.focusTimer.region-block undefined DE,FR,PL,US
browser.newtabpage.activity-stream.widgets.lists.enabled true false
browser.newtabpage.activity-stream.widgets.lists.region-block undefined DE,FR,PL,US
browser.newtabpage.activity-stream.widgets.marketGate.enabled undefined true
browser.newtabpage.activity-stream.widgets.marketGate.enforceOnNightly undefined false
browser.newtabpage.activity-stream.widgets.pictureOfTheDay.enabled true false
browser.newtabpage.activity-stream.widgets.pictureOfTheDay.region-block undefined DE,FR,PL,US
browser.newtabpage.activity-stream.widgets.privacy.enabled true false
browser.newtabpage.activity-stream.widgets.recentSearches.enabled true false
browser.newtabpage.activity-stream.widgets.sports.forceLiveDataTrustable false undefined
browser.newtabpage.activity-stream.widgets.sportsWidget.celebrations.enabled false undefined
browser.newtabpage.activity-stream.widgets.sportsWidget.celebrations.windowMs 86400000 undefined
browser.newtabpage.activity-stream.widgets.sportsWidget.enabled true undefined
browser.newtabpage.activity-stream.widgets.sportsWidget.interaction false undefined
browser.newtabpage.activity-stream.widgets.sportsWidget.live.enabled false undefined
browser.newtabpage.activity-stream.widgets.sportsWidget.pollIdleMs 21600000 undefined
browser.newtabpage.activity-stream.widgets.sportsWidget.pollLiveMs 180000 undefined
browser.newtabpage.activity-stream.widgets.sportsWidget.pollMatchDayMs 1800000 undefined
browser.newtabpage.activity-stream.widgets.sportsWidget.pollPregameLeadMs 600000 undefined
browser.newtabpage.activity-stream.widgets.sportsWidget.size undefined
browser.newtabpage.activity-stream.widgets.stocks.enabled true false
browser.newtabpage.activity-stream.widgets.system.clocks.region-block undefined PL
browser.newtabpage.activity-stream.widgets.system.crossword.locale-config undefined en-CA,en-GB,en-US
browser.newtabpage.activity-stream.widgets.system.crossword.region-block undefined PL
browser.newtabpage.activity-stream.widgets.system.enabled false true
browser.newtabpage.activity-stream.widgets.system.focusTimer.region-block undefined PL
browser.newtabpage.activity-stream.widgets.system.lists.region-block undefined PL
browser.newtabpage.activity-stream.widgets.system.pictureOfTheDay.region-block undefined PL
browser.newtabpage.activity-stream.widgets.system.region-block undefined
browser.newtabpage.activity-stream.widgets.system.sportsWidget.enabled false undefined
browser.pagethumbnails.capturing_disabled undefined true
browser.preonboarding.enabled undefined false
browser.region.network.url https://location.services.mozilla.com/v1/country?key=%MOZILLA_API_KEY%
browser.safebrowsing.blockedURIs.enabled true false
browser.safebrowsing.downloads.enabled true false
browser.safebrowsing.malware.enabled true false
browser.safebrowsing.phishing.enabled true false
browser.search.update true false
browser.sessionstore.resume_from_crash true false
browser.shell.checkDefaultBrowser true false
browser.smartwindow.aitab.viewerURL undefined
browser.smartwindow.resumeActivity.enabled undefined true
browser.smartwindow.searchTheWebAnswers undefined false
browser.startup.couldRestoreSession.count 0 -1
browser.startup.homepage_override.mstone undefined ignore
browser.tabs.remote.unloadDelayMs undefined 0
browser.tabs.warnOnCloseOtherTabs true false
browser.tabs.warnOnOpen true false
browser.toolbars.bookmarks.visibility newtab never
browser.topsites.contile.enabled true false
browser.translations.enable true false
browser.urlbar.mentions.maxGroupResults undefined 5
browser.urlbar.merino.endpointURL https://merino.services.mozilla.com/api/v1/suggest
browser.urlbar.merino.ohttpConfigURL https://ohttp-gateway-merino.services.mozilla.com/ohttp-configs
browser.urlbar.merino.ohttpRelayURL https://ohttp-merino.mozilla.fastly-edge.com
browser.urlbar.suggest.searches true false
browser.usedOnWindows10.introURL undefined
browser.warnOnQuit true false
content.notify.backoffcount -1 undefined
content.notify.interval 120000 undefined
content.notify.ontimer true undefined
datareporting.healthreport.documentServerURI undefined http://%(server)s/dummy/healthreport/
datareporting.healthreport.logging.consoleEnabled undefined false
datareporting.healthreport.service.enabled undefined false
datareporting.healthreport.service.firstRun undefined false
datareporting.healthreport.uploadEnabled true false
datareporting.policy.dataSubmissionEnabled true false
datareporting.policy.dataSubmissionPolicyAccepted undefined false
datareporting.policy.dataSubmissionPolicyBypassNotification false true
datareporting.usage.uploadEnabled true false
devtools.settings.redesign-enabled undefined false
dom.disable_open_during_load true false
dom.file.createInChild false true
dom.fs.privateBrowsing.enabled undefined false
dom.input_events.security.minNumTicks 3 0
dom.input_events.security.minTimeElapsedInMS 100 0
dom.ipc.processPriorityManager.enabled true false
dom.ipc.reportProcessHangs true false
dom.max_script_run_time 10 0
dom.navigation.navigationRateLimit.count 200 0
dom.permissions.testing.enabled false true
dom.push.connection.enabled true false
dom.push.window_pushmanager.enabled undefined false
dom.scoped-custom-element-registries.enabled false true
dom.security.sanitizer.while-parsing false true
dom.successive_dialog_time_limit undefined 0
extensions.autoDisableScopes 15 0
extensions.blocklist.detailsURL https://blocked.cdn.mozilla.net/ http://%(server)s/extensions-dummy/blocklistDetailsURL
extensions.blocklist.itemURL https://blocked.cdn.mozilla.net/%blockID%.html http://%(server)s/extensions-dummy/blocklistItemURL
extensions.enabledScopes undefined 5
extensions.formautofill.addresses.enabled true false
extensions.formautofill.addresses.supported detect on
extensions.formautofill.creditCards.enabled true false
extensions.formautofill.suppressUnrecognizedAutocomplete.enabled undefined false
extensions.getAddons.cache.enabled true false
extensions.getAddons.discovery.api_url https://services.addons.mozilla.org/api/v4/discovery/?lang=%LOCALE%&edition=%DISTRIBUTION% data:,
extensions.getAddons.get.url https://services.addons.mozilla.org/api/v4/addons/search/?guid=%IDS%&lang=%LOCALE% http://%(server)s/extensions-dummy/repositoryGetURL
extensions.getAddons.search.browseURL https://addons.mozilla.org/%LOCALE%/firefox/search?q=%TERMS%&platform=%OS%&appver=%VERSION% http://%(server)s/extensions-dummy/repositoryBrowseURL
extensions.hotfix.url undefined http://%(server)s/extensions-dummy/hotfixURL
extensions.installDistroAddons undefined false
extensions.systemAddon.update.enabled true false
extensions.update.background.url https://versioncheck-bg.addons.mozilla.org/update/VersionCheck.php?reqVersion=%REQ_VERSION%&id=%ITEM_ID%&version=%ITEM_VERSION%&maxAppVersion=%ITEM_MAXAPPVERSION%&status=%ITEM_STATUS%&appID=%APP_ID%&appVersion=%APP_VERSION%&appOS=%APP_OS%&appABI=%APP_ABI%&locale=%APP_LOCALE%&currentAppVersion=%CURRENT_APP_VERSION%&updateType=%UPDATE_TYPE%&compatMode=%COMPATIBILITY_MODE% http://%(server)s/extensions-dummy/updateBackgroundURL
extensions.update.enabled true false
extensions.update.notifyUser undefined false
extensions.update.url https://versioncheck.addons.mozilla.org/update/VersionCheck.php?reqVersion=%REQ_VERSION%&id=%ITEM_ID%&version=%ITEM_VERSION%&maxAppVersion=%ITEM_MAXAPPVERSION%&status=%ITEM_STATUS%&appID=%APP_ID%&appVersion=%APP_VERSION%&appOS=%APP_OS%&appABI=%APP_ABI%&locale=%APP_LOCALE%&currentAppVersion=%CURRENT_APP_VERSION%&updateType=%UPDATE_TYPE%&compatMode=%COMPATIBILITY_MODE% http://%(server)s/extensions-dummy/updateURL
extensions.webcompat-reporter.enabled false true
focusmanager.testmode false true
general.useragent.updates.enabled undefined false
geo.prompt.open_system_prefs true false
geo.provider.network.url https://www.googleapis.com/geolocation/v1/geolocate?key=%GOOGLE_LOCATION_SERVICE_API_KEY%&solution_channel=%OS%
geo.provider.testing undefined true
geo.wifi.scan undefined false
gfx.canvas.remote.use-draw-image-fast-path-dmabuf undefined false
identity.fxaccounts.auth.uri https://api.accounts.firefox.com/v1 https://{server}/dummy/fxa
image.natural-size-fallback.enabled true undefined
layout.css.attr.enabled true undefined
layout.css.content.alt-text.enabled true undefined
layout.css.display-grid-lanes.enabled undefined false
layout.css.grid-template-masonry-value.enabled false undefined
layout.css.namespace.exposed-in-workers-and-worklets undefined false
layout.css.scroll-driven-animations.enabled false true
media.hardware-video-decoding-vulkan.prefer-system-ffmpeg undefined false
media.videocontrols.picture-in-picture.enable-when-occluded.enabled undefined false
mousewheel.allow_scrolling_more_than_one_page false true
network.captive-portal-service.enabled true false
network.connectivity-service.enabled true false
network.http.http3.fallback_to_h2_on_protocol_error undefined true
network.http.upload_copy_max_segment_size undefined 4096
network.idn.allowed_limited_use_scripts undefined Bali, Cans, Java, Nko
network.manage-offline-status true false
network.sntp.pools undefined %(server)s
network.tcp.notsent_lowat 0 32768
network.tcp.user_timeout 0 30
network.trr.allow_default_http3_first false true
network.trr.preserve_on_background false true
permissions.isolateBy.userContext false true
privacy.trackingprotection.pbmode.enabled true false
remote.prefs.recommended.applied undefined true
security.certerrors.mitm.priming.enabled true false
security.fileuri.strict_origin_policy true false
security.notification_enable_delay 500 0
security.remote_settings.intermediates.enabled true false
security.webauthn.related_origin_requests_mode 2 1
services.settings.loglevel undefined off
services.settings.server undefined data:,#remote-settings-dummy/v1
sidebar.newTool.migration.passwords undefined {"visibilityPref":"browser.contextual-password-manager.enabled"}
signon.autofillForms true false
signon.management.page.breach-alerts.enabled true false
signon.management.page.vulnerable-passwords.enabled true false
signon.rememberSignons true false
signon.storage.rust.enabled false true
startup.homepage_welcome_url about:welcome about:blank
telemetry.fog.enable_store_submitted_pings undefined false
telemetry.fog.test.decelerate_early_events undefined false
telemetry.fog.test.localhost_port 0 -1
termsofuse.bypassNotification false true
toolkit.coverage.enabled false undefined
toolkit.coverage.endpoint.base https://coverage.mozilla.org undefined
toolkit.startup.max_resumed_crashes 3 -1
toolkit.telemetry.enabled false true
toolkit.telemetry.server https://incoming.telemetry.mozilla.org https://%(server)s/telemetry-dummy/
ui.mouse.right_click.select_in_editable undefined false
ui.mouse.right_click.select_under_cursor undefined false
widget.swipe.haptic-feedback.enabled undefined false
widget.windows.window_occlusion_tracking.enabled undefined false