This article shows the difference between the default preferences of Firefox 157.0 and Firefox 156.0. The diff table below is generated using my small script firefox-prefjs-surveyer.

Preference difference
PrefFirefox 156.0Firefox 157.0
browser.ai.control.speechRecognition undefined default
browser.discovery.containers.enabled true undefined
browser.discovery.sites addons.mozilla.org undefined
browser.highlightToSearch.copy.enabled undefined true
browser.highlightToSearch.enabled undefined true
browser.highlightToSearch.featureGate undefined false
browser.highlightToSearch.search.enabled undefined true
browser.ipProtection.openedPanelWithLocation false undefined
browser.ml.hwinference.max_restarts undefined 3
browser.netError.searchCTA.decisionTimeoutMs undefined 300
browser.newtabpage.activity-stream.discoverystream.locale-list-config undefined
browser.newtabpage.activity-stream.discoverystream.region-stories-config US,DE,CA,GB,IE,CH,AT,BE,IN,FR,IT,ES undefined
browser.newtabpage.activity-stream.discoverystream.sections.topicNavigation.enabled undefined false
browser.newtabpage.activity-stream.newtabWallpapers.customWallpaper.library.enabled undefined false
browser.newtabpage.activity-stream.newtabWallpapers.customWallpaper.nextNumber undefined 1
browser.newtabpage.activity-stream.newtabWallpapers.customWallpaper.position undefined
browser.newtabpage.activity-stream.pageLayouts.autoMinimizeDelayMs undefined 3000
browser.newtabpage.activity-stream.privacyInfo.url https://support.mozilla.org/1/firefox/156.0/Linux/en-US/sponsor-privacy https://support.mozilla.org/1/firefox/157.0/Linux/en-US/sponsor-privacy
browser.newtabpage.activity-stream.sectionsLearnMore.url https://support.mozilla.org/1/firefox/156.0/Linux/en-US/firefox-new-tab-personalization https://support.mozilla.org/1/firefox/157.0/Linux/en-US/firefox-new-tab-personalization
browser.newtabpage.activity-stream.support.url https://support.mozilla.org/1/firefox/156.0/Linux/en-US/new-tab https://support.mozilla.org/1/firefox/157.0/Linux/en-US/new-tab
browser.newtabpage.activity-stream.widgets.autoMinimize.userOverride undefined false
browser.newtabpage.activity-stream.widgets.recentSearches.tab undefined recent
browser.nova.enabled false true
browser.resourceMonitor.enabled undefined false
browser.safebrowsing.provider.mozilla.lists base-track-digest256,mozstd-trackwhite-digest256,google-trackwhite-digest256,content-track-digest256,mozplugin-block-digest256,mozplugin2-block-digest256,ads-track-digest256,social-track-digest256,analytics-track-digest256,base-fingerprinting-track-digest256,content-fingerprinting-track-digest256,base-cryptomining-track-digest256,content-cryptomining-track-digest256,fanboyannoyance-ads-digest256,fanboysocial-ads-digest256,easylist-ads-digest256,easyprivacy-ads-digest256,adguard-ads-digest256,social-tracking-protection-digest256,social-tracking-protection-facebook-digest256,social-tracking-protection-linkedin-digest256,social-tracking-protection-twitter-digest256,base-email-track-digest256,content-email-track-digest256,consent-manager-track-digest256,anti-fraud-track-digest256,harmful-addon-block-digest256,harmful-addon-entitylist-digest256 base-track-digest256,mozstd-trackwhite-digest256,google-trackwhite-digest256,content-track-digest256,ads-track-digest256,social-track-digest256,analytics-track-digest256,base-fingerprinting-track-digest256,content-fingerprinting-track-digest256,base-cryptomining-track-digest256,content-cryptomining-track-digest256,fanboyannoyance-ads-digest256,fanboysocial-ads-digest256,easylist-ads-digest256,easyprivacy-ads-digest256,adguard-ads-digest256,social-tracking-protection-digest256,social-tracking-protection-facebook-digest256,social-tracking-protection-linkedin-digest256,social-tracking-protection-twitter-digest256,base-email-track-digest256,content-email-track-digest256,consent-manager-track-digest256,anti-fraud-track-digest256,harmful-addon-block-digest256,harmful-addon-entitylist-digest256
browser.search.separatePrivateDefault true undefined
browser.search.separatePrivateDefault.enabled undefined false
browser.search.separatePrivateDefault.featureGate undefined false
browser.search.separatePrivateDefault.ui.enabled false undefined
browser.smartwindow.agent.monitorAnnouncement undefined false
browser.smartwindow.conversationHistory.logLevel undefined Error
browser.smartwindow.conversationStore.logLevel undefined Error
browser.tabs.remote.enforceRemoteTypeRestrictions false undefined
browser.touchmode.auto true false
browser.urlbar.searchModeSwitcher.skipTabStop false true
devtools.inspector.split-orientation undefined auto
dom.ipc.utilityProcess.shutdownTimeoutSecs undefined 5
dom.navigation.navigationRateLimit.count 1000 200
dom.security.sanitizer.while-parsing undefined false
dom.webcrypto.encapsulation.enabled undefined false
dom.webnotifications.navigate.enabled undefined false
extensions.formautofill.addresses.storage.rust.active undefined false
extensions.formautofill.addresses.storage.rust.enabled undefined false
extensions.formautofill.addresses.storage.rust.migrationAttempts undefined 0
extensions.formautofill.addresses.storage.rust.migrationTestVersion undefined 0
extensions.formautofill.addresses.storage.rust.runMigrationTest undefined false
extensions.formautofill.useml.features undefined []
extensions.formautofill.useml.ignoreFieldTypes undefined
extensions.formautofill.useml.modelVersion undefined
gfx.e10s.font-list.shared true undefined
gfx.font_rendering.fontconfig.skip_legacy_fonts undefined false
gfx.webrender.debug.alpha-primitives false undefined
gfx.webrender.debug.slow-frame-indicator false undefined
gfx.webrender.layer-compositor false true
idle_period.cross_process_scheduling true undefined
image.exif-density-correction.sanity-check.enabled true undefined
image.jxl.decode_participants undefined 0
layout.css.supports.at-rule.enabled false true
media.decoder.frame-color-metadata.enabled undefined false
media.eme.encrypted-media-encryption-scheme.enabled true undefined
media.getusermedia.camera.fake.rotation undefined 0
media.getusermedia.camera.fake.rotation-test-pattern undefined false
media.mediacapabilities.codec-support-cache.enabled undefined false
media.mediacapabilities.drop-threshold 95 undefined
media.navigator.mediadatadecoder_av1_enabled false true
media.rvfc.enabled true undefined
media.webspeech.recognition.idle_shutdown_grace_ms undefined 5000
media.webspeech.recognition.install_on_start undefined true
media.webspeech.recognition.testing.parakeet_init_delay_ms undefined 0
media.webspeech.test.fake_fsm_events false undefined
media.webspeech.test.fake_recognition_service false undefined
network.cookie.db.flushIntervalMs undefined 500
network.cookie.prevent_set_cookie_from_multipart true undefined
network.http.origin.redirectTainted true undefined
network.negotiate-auth.using-native-gsslib true undefined
pdfjs.handleFrameAttributeLoads undefined true
privacy.clearSiteDataHeader.cache.bfcache.enabled true undefined
privacy.globalprivacycontrol.functionality.enabled true undefined
security.tls.client_hello.send_p256_keyshare true undefined
security.tls.enable_mldsa undefined false
sidebar.newTool.migration.resourcemonitor undefined {"visibilityPref":"browser.resourceMonitor.enabled"}
sidebar.revamp false true
signon.storage.rust.restoreAttemptsVersion undefined 0
signon.storage.rust.restoreDone false undefined
signon.storage.rust.restoreTargetVersion undefined 1
signon.storage.rust.restoreVersion undefined 0
toolkit.telemetry.updatePing.enabled true undefined
urlclassifier.disallow_completions goog-downloadwhite-digest256,base-track-digest256,mozstd-trackwhite-digest256,content-track-digest256,mozplugin-block-digest256,mozplugin2-block-digest256,ads-track-digest256,social-track-digest256,analytics-track-digest256,base-fingerprinting-track-digest256,content-fingerprinting-track-digest256,base-cryptomining-track-digest256,content-cryptomining-track-digest256,fanboyannoyance-ads-digest256,fanboysocial-ads-digest256,easylist-ads-digest256,easyprivacy-ads-digest256,adguard-ads-digest256,social-tracking-protection-digest256,social-tracking-protection-facebook-digest256,social-tracking-protection-linkedin-digest256,social-tracking-protection-twitter-digest256,base-email-track-digest256,content-email-track-digest256,consent-manager-track-digest256,anti-fraud-track-digest256,harmful-addon-block-digest256 goog-downloadwhite-digest256,base-track-digest256,mozstd-trackwhite-digest256,content-track-digest256,ads-track-digest256,social-track-digest256,analytics-track-digest256,base-fingerprinting-track-digest256,content-fingerprinting-track-digest256,base-cryptomining-track-digest256,content-cryptomining-track-digest256,fanboyannoyance-ads-digest256,fanboysocial-ads-digest256,easylist-ads-digest256,easyprivacy-ads-digest256,adguard-ads-digest256,social-tracking-protection-digest256,social-tracking-protection-facebook-digest256,social-tracking-protection-linkedin-digest256,social-tracking-protection-twitter-digest256,base-email-track-digest256,content-email-track-digest256,consent-manager-track-digest256,anti-fraud-track-digest256,harmful-addon-block-digest256
webgl.can-lose-context-in-foreground true undefined
widget.use-xdg-desktop-portal.native-messaging-proxy undefined 0