This article shows the difference between the default preferences of Firefox 155.0 beta 5 and Firefox 154.0.1. The diff table below is generated using my small script firefox-prefjs-surveyer.

Preference difference
PrefFirefox 154.0.1Firefox 155.0 beta 5
accessibility.ARIAElementReflection.enabled true undefined
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.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.rounded_external_scroll_offset false undefined
browser.aboutaddons.novaThemesPickerEnabled undefined true
browser.alerts.capture.enabled undefined true
browser.ctrlTab.maxPreviews undefined 7
browser.ipProtection.features.siteInclusions undefined false
browser.ml.onnxNativeAvailabilityReported undefined false
browser.netError.searchCTA.enabled undefined false
browser.newtabpage.activity-stream.discoverystream.sections.adAllowedRanks undefined
browser.newtabpage.activity-stream.discoverystream.sections.layout 7-double-row-2-ad undefined
browser.newtabpage.activity-stream.discoverystream.sections.ordering undefined
browser.newtabpage.activity-stream.discoverystream.thumbsUpDown.locale-thumbs-config en-US, en-GB, en-CA undefined
browser.newtabpage.activity-stream.discoverystream.thumbsUpDown.region-thumbs-config US undefined
browser.newtabpage.activity-stream.discoverystream.thumbsUpDown.searchTopsitesCompact true undefined
browser.newtabpage.activity-stream.feeds.webnotificationsfeed false true
browser.newtabpage.activity-stream.logo.variation undefined
browser.newtabpage.activity-stream.privacyInfo.url https://support.mozilla.org/1/firefox/154.0.1/Linux/en-US/sponsor-privacy https://support.mozilla.org/1/firefox/155.0/Linux/en-US/sponsor-privacy
browser.newtabpage.activity-stream.sectionsLearnMore.url https://support.mozilla.org/1/firefox/154.0.1/Linux/en-US/firefox-new-tab-personalization https://support.mozilla.org/1/firefox/155.0/Linux/en-US/firefox-new-tab-personalization
browser.newtabpage.activity-stream.showWebNotifications undefined true
browser.newtabpage.activity-stream.support.url https://support.mozilla.org/1/firefox/154.0.1/Linux/en-US/new-tab https://support.mozilla.org/1/firefox/155.0/Linux/en-US/new-tab
browser.newtabpage.activity-stream.system.showWebNotifications undefined false
browser.newtabpage.activity-stream.widgets.clocks.interaction undefined false
browser.newtabpage.activity-stream.widgets.privacy.blankChance undefined 0.4
browser.newtabpage.activity-stream.widgets.privacy.celebrationState undefined {}
browser.newtabpage.activity-stream.widgets.privacy.celebrationThreshold undefined 10
browser.newtabpage.activity-stream.widgets.privacy.forceCelebration undefined
browser.newtabpage.activity-stream.widgets.privacy.forceMessageId undefined
browser.newtabpage.activity-stream.widgets.privacy.maxDisplayCount undefined 999
browser.newtabpage.activity-stream.widgets.privacy.messageState undefined {}
browser.newtabpage.activity-stream.widgets.privacy.showVpnMessages undefined false
browser.newtabpage.activity-stream.widgets.stocks.interaction undefined false
browser.pageextractor.youtube.enabled undefined false
browser.pageextractor.youtube.timeoutMs undefined 3000
browser.promo.cookiebanners.enabled false undefined
browser.promo.focus.disallowed_regions cn undefined
browser.promo.focus.enabled true undefined
browser.referrals.code undefined
browser.referrals.pingSubmitted undefined false
browser.smartwindow.agent.enabled undefined true
browser.smartwindow.agent.supportedRegions undefined US,CA
browser.smartwindow.endpoint https://mlpa-prod-prod-mozilla.global.ssl.fastly.net/v1 https://mlpa-prod-prod-mozilla.freetls.fastly.net/v1
browser.smartwindow.firstrun.explainerURL https://www.firefox.com/en-US/smart-window/?v=product https://www.firefox.com/smart-window/?v=product
browser.smartwindow.mistralRelease false true
browser.smartwindow.searchQuery.endpointURL https://mlpa-prod-prod-mozilla.global.ssl.fastly.net/v1/search https://mlpa-prod-prod-mozilla.freetls.fastly.net/v1/search
browser.smartwindow.searchTheWebFast undefined true
browser.smartwindow.smartformfill.disallowedRegions undefined FR
browser.smartwindow.smartformfill.enabled undefined false
browser.tabs.groups.onboardingCallouts.enabled undefined false
browser.tabs.groups.smart.agglomerativeThresholdInt 825 650
browser.translation.neverForLanguages undefined
browser.urlbar.deduplication.thresholdDays 0 undefined
browser.urlbar.share-button.enabled undefined false
browser.urlbar.trackerCount.enabled undefined true
browser.urlbar.trackerCount.featureGate undefined false
browser.urlbar.trimWww undefined false
captivedetect.canonicalContent <meta http-equiv="refresh" content="0;url=https://support.mozilla.org/kb/captive-portal"/>
captivedetect.canonicalURL http://detectportal.firefox.com/canonical.html http://firefox-portal-detection.com/generate_204
cookiebanners.bannerClicking.enabled true undefined
cookiebanners.bannerClicking.logLevel Error undefined
cookiebanners.bannerClicking.maxTriesPerSiteAndSession 3 undefined
cookiebanners.bannerClicking.pollingInterval 500 undefined
cookiebanners.bannerClicking.testing false undefined
cookiebanners.bannerClicking.timeoutAfterDOMContentLoaded 20000 undefined
cookiebanners.bannerClicking.timeoutAfterLoad 5000 undefined
cookiebanners.cookieInjector.defaultExpiryRelative 31536000 undefined
cookiebanners.cookieInjector.enabled true undefined
cookiebanners.listService.logLevel Error undefined
cookiebanners.listService.testRules [] undefined
cookiebanners.listService.testSkipRemoteSettings false undefined
cookiebanners.service.detectOnly false undefined
cookiebanners.service.enableGlobalRules true undefined
cookiebanners.service.enableGlobalRules.subFrames true undefined
cookiebanners.service.mode 0 undefined
cookiebanners.service.mode.privateBrowsing 0 undefined
cookiebanners.ui.desktop.showCallout false undefined
devtools.debugger.file-search-case-sensitive false undefined
devtools.debugger.file-search-regex-match false undefined
devtools.debugger.file-search-whole-word false undefined
dom.editcontext.suppress_notifying_ime_timeout undefined 300
dom.editcontext.suppress_notifying_ime_timeout_focus undefined 100
dom.ipc.validatePrincipal.validateSiteLoaded undefined true
dom.origin-trials.private-attribution.state 0 undefined
dom.performance.deliverytype.enabled undefined false
dom.private-attribution.submission.enabled false undefined
dom.security.credentialmanagement.chooser.testing.enabled false undefined
dom.speculation_rules.max_body_bytes undefined 5242880
dom.speculation_rules.max_records_per_document undefined 20
dom.speculation_rules.record_expiry_ms undefined 300000
dom.speculation_rules.same_origin_only undefined true
dom.speculation_rules.wait_timeout_ms undefined 2000
dom.vr.controller.enumerate.interval 1000 undefined
extensions.formautofill.addresses.supported detect on
extensions.formautofill.passports.enabled undefined false
extensions.formautofill.passports.supported undefined off
extensions.webcompat-reporter.enabled false true
gfx.font_rendering.colr_v1.enabled true undefined
gfx.webrender.debug.color-target-init undefined false
gfx.webrender.render-backend-thread-count undefined 2
gfx.webrender.shared-instance-buffer undefined true
gfx.webrender.trim-paused-renderers.mode undefined 2
javascript.options.experimental.explicit_resource_management true undefined
javascript.options.experimental.promise_allkeyed undefined true
javascript.options.wasm_compact_imports false true
javascript.options.wasm_wide_arithmetic false true
layout.css.alpha-color-function.enabled false true
layout.css.anchor-positioning.enabled true undefined
layout.css.attr.enabled false true
layout.css.calc-typed-arithmetic.enabled undefined false
layout.css.display-animations.enabled undefined false
layout.css.fake-webkit-scrollbar.disabled-domains discord.com,shitposter.world,gemini.google.com,content.powerapps.com undefined
layout.css.fake-webkit-scrollbar.enabled-domains undefined mail.google.com,docs.google.com,play.google.com,polymarket.com,www.beterbed.nl,www.shazam.com,www.tiktok.com
layout.css.font-palette.enabled true undefined
layout.css.font-tech.enabled true undefined
layout.css.font-variant-emoji.enabled true undefined
layout.css.font-variations.enabled true undefined
layout.css.progress-function.enabled false true
layout.css.supports.at-rule.enabled undefined false
mathml.a.element.enabled undefined false
media.benchmark.frames 300 undefined
media.benchmark.timeout 1000 undefined
media.benchmark.vp9.fps 0 undefined
media.benchmark.vp9.threshold 150 undefined
media.benchmark.vp9.versioncheck 0 undefined
media.use-remote-encoder.audio false undefined
media.use-remote-encoder.audio.software undefined false
media.use-remote-encoder.video false undefined
media.use-remote-encoder.video.platform undefined false
media.use-remote-encoder.video.software undefined false
media.videocontrols.picture-in-picture.playback-speed.enabled undefined false
network.connectivity-service.IPv4.url http://detectportal.firefox.com/success.txt?ipv4 http://firefox-portal-detection.com/success.txt?ipv4
network.connectivity-service.IPv6.url http://detectportal.firefox.com/success.txt?ipv6 http://firefox-portal-detection.com/success.txt?ipv6
network.http.happy_eyeballs_enabled false true
network.http.http3.max_gso_segments 10 64
network.http.http3.version_negotiation.enabled false true
network.protocol-handler.prompt-without-user-activation undefined true
pdfjs.enableNova undefined true
pdfjs.featuresNotificationDismissed undefined false
places.semanticHistory.embeddingType static
places.semanticHistory.multilingualEmbeddingRegions undefined [["FR",["en-*","fr-*"]],["*",["fr-*"]]]
places.semanticHistory.supportedRegions [["AU",["en-*"]],["CA",["en-*"]],["GB",["en-*"]],["IE",["en-*"]],["NZ",["en-*"]],["PH",["en-*"]],["US",["en-*"]]] [["AU",["en-*"]],["CA",["en-*"]],["GB",["en-*"]],["IE",["en-*"]],["NZ",["en-*"]],["PH",["en-*"]],["US",["en-*"]],["FR",["en-*","fr-*"]]]
privacy.containers.switchDuringNavigation.enabled undefined false
remote.experimental.dynamicstart.enabled undefined false
remote.screenshot.use_readback undefined false
security.allow_unsafe_subscript_loads undefined false
sidebar.openTabsPanel.hoverPreview.enabled undefined true
sidebar.openTabsPanel.sortOption undefined tabStripOrder
sidebar.revamp.round-content-area true undefined
signon.storage.rust.enabled false true
svg.Moz2D.strokeBounds.enabled false true
svg.SVGAElement.text.enabled false undefined
svg.new-getBBox.enabled false true
toolkit.telemetry.dap_enabled false undefined
toolkit.telemetry.dap_task1_enabled false undefined
toolkit.telemetry.dap_task1_taskid undefined
toolkit.telemetry.dap_visit_counting_enabled false undefined
toolkit.telemetry.dap_visit_counting_experiment_list [] undefined
toolkit.telemetry.enabled false true
ui.new-webcompat-reporter.send-more-info-link false undefined