This is difference between the default preference of Firefox 137.0 beta 6 and one of 136.0.1. This diff table is generated with my small script firefox-prefjs-surveyer.

Preference difference
PrefFirefox 136.0.1Firefox 137.0 beta 6
app.normandy.test-prefs.bool undefined false
app.normandy.test-prefs.integer undefined 0
app.normandy.test-prefs.string undefined
app.releaseNotesURL https://www.mozilla.org/%LOCALE%/firefox/%VERSION%/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-desktop&utm_campaign=whatsnew https://www.mozilla.org/%LOCALE%/firefox/%VERSION%beta/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-desktop&utm_campaign=whatsnew
app.releaseNotesURL.aboutDialog https://www.mozilla.org/%LOCALE%/firefox/%VERSION%/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-desktop&utm_campaign=about-dialog https://www.mozilla.org/%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
browser.cache.disk.metadata_memory_limit 250 1024
browser.contentanalysis.agent_timeout 30 300
browser.contentanalysis.interception_point.clipboard.plain_text_only undefined true
browser.contentanalysis.interception_point.drag_and_drop.plain_text_only undefined true
browser.contentanalysis.timeout_result undefined 0
browser.contentblocking.features.strict tp,tpPrivate,cookieBehavior5,cookieBehaviorPBM5,cm,fp,stp,emailTP,emailTPPrivate,lvl2,rp,rpTop,ocsp,qps,qpsPBM,fpp,fppPrivate,3pcd,btp tp,tpPrivate,cookieBehavior5,cookieBehaviorPBM5,cm,fp,stp,emailTP,emailTPPrivate,lvl2,rp,rpTop,ocsp,qps,qpsPBM,fpp,fppPrivate,btp
browser.contextual-password-manager.enabled undefined false
browser.crashReporter.memtest undefined true
browser.crashReporter.memtestKinds undefined
browser.crashReports.crashPull undefined false
browser.crashReports.requestedNeverShowAgain undefined false
browser.http.blank_page_with_error_response.enabled true false
browser.newtabpage.activity-stream.caretBlinkCount undefined -1
browser.newtabpage.activity-stream.caretBlinkTime undefined 567
browser.newtabpage.activity-stream.discoverystream.publisherFavicon.enabled undefined false
browser.newtabpage.activity-stream.discoverystream.sections.interestPicker.enabled undefined false
browser.newtabpage.activity-stream.discoverystream.sections.interestPicker.visibleSections undefined
browser.newtabpage.activity-stream.discoverystream.sections.personalization.inferred.enabled undefined false
browser.newtabpage.activity-stream.discoverystream.sections.topicSelection.enabled false undefined
browser.newtabpage.activity-stream.discoverystream.thumbsUpDown.region-thumbs-config US, CA
browser.newtabpage.activity-stream.images.smart undefined true
browser.newtabpage.activity-stream.newtabLogo.aprilfools false undefined
browser.newtabpage.activity-stream.newtabWallpapers.customWallpaper.enabled undefined false
browser.newtabpage.activity-stream.newtabWallpapers.customWallpaper.uploadedPreviously undefined false
browser.newtabpage.activity-stream.newtabWallpapers.wallpaper-dark undefined
browser.newtabpage.activity-stream.newtabWallpapers.wallpaper-light undefined
browser.newtabpage.activity-stream.support.url https://support.mozilla.org/1/firefox/136.0.1/Linux/en-US/new-tab https://support.mozilla.org/1/firefox/137.0/Linux/en-US/new-tab
browser.newtabpage.activity-stream.telemetry.ut.events false true
browser.newtabpage.activity-stream.unifiedAds.spocs.enabled false true
browser.newtabpage.activity-stream.unifiedAds.tiles.enabled false true
browser.newtabpage.activity-stream.weather.temperatureUnits f c
browser.preonboarding.onTrainRolloutPopulation undefined 0
browser.safebrowsing.only_top_level undefined false
browser.sessionstore.log.appender.file.logOnSuccess false true
browser.sessionstore.loglevel Warn Debug
browser.shopping.experience2023.autoClose.userEnabled undefined true
browser.shopping.experience2023.newPositionCard.hasSeen undefined false
browser.tabs.dragdrop.moveOverThresholdPercent 70 80
browser.tabs.fadeOutUnloadedTabs undefined false
browser.tabs.groups.dragOverDelayMS 120 240
browser.tabs.groups.dragOverThresholdPercent 20 undefined
browser.tabs.groups.enabled false true
browser.tabs.groups.smart.enabled undefined false
browser.urlbar.quicksuggest.allowPositionInSuggestions true undefined
browser.urlbar.quicksuggest.contextualOptIn.dismissedCount undefined 0
browser.urlbar.quicksuggest.contextualOptIn.firstReshowAfterPeriodDays undefined 7
browser.urlbar.quicksuggest.contextualOptIn.impressionCount undefined 0
browser.urlbar.quicksuggest.contextualOptIn.impressionDaysLimit undefined 5
browser.urlbar.quicksuggest.contextualOptIn.impressionLimit undefined 20
browser.urlbar.quicksuggest.contextualOptIn.sayHello false undefined
browser.urlbar.quicksuggest.contextualOptIn.secondReshowAfterPeriodDays undefined 14
browser.urlbar.quicksuggest.contextualOptIn.thirdReshowAfterPeriodDays undefined 60
browser.urlbar.quicksuggest.contextualOptIn.topPosition true undefined
browser.urlbar.quicksuggest.hideSettingsUI false undefined
browser.urlbar.quicksuggest.settingsUi undefined 0
browser.urlbar.quicksuggest.shouldShowOnboardingDialog false undefined
browser.urlbar.quicksuggest.showOnboardingDialogAfterNRestarts 0 undefined
browser.urlbar.scotchBonnet.enableOverride false true
browser.urlbar.suggest.calculator false true
devtools.netmonitor.columnsData [{"name":"status","minWidth":30,"width":5}, {"name":"method","minWidth":30,"width":5}, {"name":"domain","minWidth":30,"width":10}, {"name":"file","minWidth":30,"width":25}, {"name":"url","minWidth":30,"width":25},{"name":"initiator","minWidth":30,"width":10},{"name":"type","minWidth":30,"width":5},{"name":"transferred","minWidth":30,"width":10},{"name":"contentSize","minWidth":30,"width":5},{"name":"waterfall","minWidth":150,"width":15}] [{"name":"override","minWidth":20,"width":2}, {"name":"status","minWidth":30,"width":5}, {"name":"method","minWidth":30,"width":5}, {"name":"domain","minWidth":30,"width":10}, {"name":"file","minWidth":30,"width":25}, {"name":"url","minWidth":30,"width":25},{"name":"initiator","minWidth":30,"width":10},{"name":"type","minWidth":30,"width":5},{"name":"transferred","minWidth":30,"width":10},{"name":"contentSize","minWidth":30,"width":5},{"name":"waterfall","minWidth":150,"width":15}]
devtools.netmonitor.features.search true undefined
devtools.netmonitor.visibleColumns ["status","method","domain","file","initiator","type","transferred","contentSize","waterfall"] ["override","status","method","domain","file","initiator","type","transferred","contentSize","waterfall"]
dom.compression_streams.enabled true undefined
dom.cookieStore.enabled true false
dom.document.edit_command.contentReadOnly.enabled true false
dom.document.edit_command.insertBrOnReturn.enabled true false
dom.event.keypress.key.allow_lone_surrogate true false
dom.fetchKeepalive.request_limit_per_origin 250 256
dom.fetchKeepalive.total_request_limit 500 2048
dom.media.webcodecs.h265.enabled undefined false
dom.security.setHTML.enabled false undefined
dom.security.unexpected_system_load_telemetry_enabled false true
dom.serviceWorkers.disable_open_click_delay 1000 undefined
dom.svg.pathSegment.enabled false true
dom.text_fragments.create_text_fragment.timeout_seconds undefined 5
dom.viewTransitions.remain-active undefined false
dom.webnotifications.disable_open_click_delay undefined 1000
dom.webnotifications.requireinteraction.enabled false true
extensions.webcompat-reporter.enabled false true
gfx.wayland.hdr undefined false
gfx.webrender.debug.missing-snapshot-panic undefined false
gfx.webrender.debug.missing-snapshot-pink undefined false
javascript.options.array_grouping true undefined
javascript.options.arraybuffer_transfer true undefined
javascript.options.destructuring_fuse true undefined
javascript.options.experimental.arraybuffer_resizable true undefined
javascript.options.experimental.atomics_pause undefined true
javascript.options.experimental.dictionary_teleporting undefined true
javascript.options.experimental.float16array true undefined
javascript.options.experimental.import_attributes undefined false
javascript.options.experimental.math_sumprecise undefined true
javascript.options.experimental.new_set_methods true undefined
javascript.options.experimental.regexp_escape true undefined
javascript.options.experimental.sharedarraybuffer_growable true undefined
javascript.options.weakrefs true undefined
javascript.options.well_formed_unicode_strings true undefined
layout.css.hyphenate-limit-chars.enabled false true
layout.css.letter-spacing.model 0 2
layout.css.style-queries.enabled undefined false
layout.css.video-dynamic-range.allows-high false true
layout.dynamic-reflow-roots.enabled false true
media.ffmpeg.encoder.cpu-used undefined 7
media.ffmpeg.vaapi.enabled false undefined
media.ffvpx-hw.enabled false true
media.hevc.enabled undefined true
media.ondevicechange.enabled true undefined
media.peerconnection.dtls.version.max 772 771
media.webrtc.enable_pq_dtls false true
media.webrtc.simulcast.vp9.enabled false true
memory.lazypurge.reuse_grace_period undefined 500
messaging-system.rsexperimentloader.enabled true undefined
network.auth.use_redirect_for_retries false true
network.dns.get-ttl true false
network.essential_domains_fallback undefined false
network.http.http3.idle_timeout undefined 30
network.http.http3.retry_different_ip_family false true
network.http.http3.sni-slicing undefined true
network.http.http3.use_nspr_for_io true false
network.http.retry_with_another_half_open false true
network.http.skip_alt_svc_validation_on_https_rr undefined true
network.jar.record_failure_reason false true
network.predictor.enable-prefetch false true
network.socket.ip_addr_any.disabled false true
network.trr.display_fallback_warning false undefined
network.trr.fallback_warning_heuristic_list canary undefined
network.trr.idle_timeout_for_http3_conn undefined 400
network.trr_ui.show_fallback_warning_option false undefined
pdfjs.enableAltTextForEnglish undefined false
pdfjs.enableAutoLinking undefined true
pdfjs.enableHighlightFloatingButton false true
pdfjs.enableSignatureEditor undefined true
pdfjs.enableUpdatedAddImage false true
places.frecency.pages.alternative.interactions.manyKeypresses undefined 50
places.frecency.pages.alternative.interactions.maxVisitGapSeconds undefined 120
places.frecency.pages.alternative.interactions.viewTimeIfManyKeypressesSeconds undefined 20
places.frecency.pages.alternative.interactions.viewTimeSeconds undefined 60
places.frecency.pages.alternative.maxDaysFromToday undefined 60
places.frecency.pages.alternative.veryHighWeight undefined 200
security.browser_xhtml_csp.report-only undefined false
security.disallow_non_local_systemprincipal_in_tests undefined false
security.pki.crlite_channel all default
security.pki.crlite_mode 3 2
security.remote_settings.crlite_filters.enabled false true
security.ssl3.ecdhe_ecdsa_aes_128_sha true false
security.ssl3.ecdhe_ecdsa_aes_256_sha true false
services.sync.engine.bookmarks.validation.enabled undefined true
services.sync.engine.passwords.validation.enabled undefined true
sidebar.animation.expand-on-hover.duration-ms undefined 400
sidebar.expandOnHover undefined false
sidebar.new-sidebar.has-used undefined false
sidebar.old-sidebar.has-used undefined false
svg.discard.enabled false true
toolkit.shopping.experience2023.defr undefined false
toolkit.telemetry.enabled false true
ui.new-webcompat-reporter.send-more-info-link false true
webextensions.storage.session.enforceQuota false true