This article shows the difference between the default preferences of Firefox 151.0 beta 10 and Firefox 150.0.3. The diff table below is generated using my small script firefox-prefjs-surveyer.

Preference difference
PrefFirefox 151.0 beta 10Firefox 150.0.3
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.aboutwelcome.experimentsGate.maxDisplayMs undefined 8000
browser.aboutwelcome.experimentsGate.minDisplayMs undefined 3000
browser.aboutwelcome.experimentsGate.skipSplashIfLoaded undefined true
browser.backup.archive.enabled false true
browser.backup.restore.enabled false true
browser.contentblocking.features.strict tp,tpPrivate,cookieBehavior5,cookieBehaviorPBM5,cryptoTP,fp,stp,emailTP,emailTPPrivate,-consentmanagerSkip,-consentmanagerSkipPrivate,lvl2,rp,rpTop,ocsp,qps,qpsPBM,fpp,fppPrivate,btp,lna tp,tpPrivate,cookieBehavior5,cookieBehaviorPBM5,cryptoTP,fp,stp,emailTP,emailTPPrivate,-consentmanagerSkip,-consentmanagerSkipPrivate,lvl2,rp,rpTop,qps,qpsPBM,fpp,fppPrivate,btp,lna
browser.contentsharing.enabled undefined false
browser.contentsharing.newBadge.enabled undefined true
browser.design-tokens.nova false undefined
browser.display.use_system_colors false undefined
browser.firefox-view.max-history-rows 0 undefined
browser.ipProtection.bandwidth.maxInGb undefined 50
browser.ipProtection.egressLocation undefined
browser.ipProtection.egressLocationEnabled false undefined
browser.ipProtection.locationButtonBadgeDismissed undefined false
browser.ipProtection.openedPanelWithLocation undefined false
browser.migrate.ie.enabled false undefined
browser.newtabpage.activity-stream.discoverystream.shortcuts.personalization.enabled false true
browser.newtabpage.activity-stream.newtabWallpapers.initialWallpaper undefined
browser.newtabpage.activity-stream.newtabWallpapers.user.enabled undefined false
browser.newtabpage.activity-stream.nova.enabled false true
browser.newtabpage.activity-stream.privacyInfo.url https://support.mozilla.org/1/firefox/150.0.3/Linux/en-US/sponsor-privacy https://support.mozilla.org/1/firefox/151.0/Linux/en-US/sponsor-privacy
browser.newtabpage.activity-stream.remote-renderer.enabled undefined false
browser.newtabpage.activity-stream.support.url https://support.mozilla.org/1/firefox/150.0.3/Linux/en-US/new-tab https://support.mozilla.org/1/firefox/151.0/Linux/en-US/new-tab
browser.newtabpage.activity-stream.widgets.defaultSize undefined large
browser.newtabpage.activity-stream.widgets.enabled false true
browser.newtabpage.activity-stream.widgets.focusTimer.size undefined large
browser.newtabpage.activity-stream.widgets.lists.size undefined large
browser.newtabpage.activity-stream.widgets.maximized false true
browser.newtabpage.activity-stream.widgets.system.weather.enabled undefined false
browser.newtabpage.activity-stream.widgets.weather.enabled undefined true
browser.newtabpage.activity-stream.widgets.weather.size undefined small
browser.nova.enabled undefined false
browser.privatebrowsing.resetPBM.enabled false true
browser.smartwindow.nova.enabled undefined false
browser.smartwindow.worldcup.enabled undefined false
browser.smartwindow.worldcup.endpointURL undefined https://merino.services.mozilla.com
browser.smartwindow.worldcup.timeoutMs undefined 2000
browser.startup.preXulSkeletonUI undefined false
browser.urlbar.autoFill.adaptiveHistory.backspaceBlockDurationMs 172800000 undefined
browser.urlbar.autoFill.adaptiveHistory.dismissalBlockDurationMs 604800000 undefined
browser.urlbar.autoFill.backspaceBlockDurationMs undefined 172800000
browser.urlbar.autoFill.backspaceThreshold undefined 3
browser.urlbar.autoFill.dismissalBlockDurationMs undefined 604800000
browser.urlbar.nova.featureGate false undefined
browser.urlbar.resultExplanations.featureGate undefined false
cookiebanners.ui.desktop.enabled false undefined
devtools.command-button-jstracer.enabled undefined false
devtools.inspector.css-explainers undefined false
dom.custom_elements.relaxed_names.enabled true undefined
dom.documentpip.enabled false true
dom.element.commandfor.enabled true undefined
dom.fetch.validatePrincipalForRemoteType undefined true
dom.fullscreen.keyboard_lock.enabled undefined true
dom.fullscreen.keyboard_lock.long_press_interval undefined 1500
dom.fullscreen.keyboard_lock.long_press_warning_interval undefined 500
dom.fullscreen.keyboard_lock.triple_click_warn_interval undefined 500
dom.navigation.api.internal_method_tracker false undefined
dom.script_loader.disk_cache_delay_ms undefined 10000
dom.shadowdom.selection_across_boundary.enabled true undefined
dom.shadowdom.shadowRootSlotAssignment.enabled undefined true
dom.webserial.enabled undefined true
dom.webserial.gated undefined true
dom.webserial.testing.enabled undefined false
dom.xslt.enabled undefined true
extensions.formautofill.addresses.supportedCountries US,CA,GB,FR,DE,BR,ES,JP,AT,IN,IT,PL,AU US,CA,GB,FR,DE,BR,ES,JP,AT,IN,IT,PL,AU,NL
extensions.webcompat-reporter.enabled false true
full-screen-api.keyboardlock-warning.timeout undefined 4000
gfx.color_management.hdr undefined false
gfx.color_management.hdr.force_enabled undefined false
gfx.color_management.hdr_video true undefined
gfx.color_management.hdr_video_assume_rec2020_uses_pq true undefined
gfx.wayland.hdr false undefined
gfx.wayland.hdr.force-enabled false undefined
gfx.webrender.enable-item-cache false undefined
gfx.webrender.precise-linear-gradients true undefined
gfx.webrender.precise-linear-gradients-swgl true undefined
identity.sendtab.deviceissues.url undefined https://support.mozilla.org/1/firefox/%VERSION%/%OS%/%LOCALE%/send-tab#w_i-dont-see-my-device-listed
image.cache.size 5242880 20971520
intl.icu4x.segmenter.enabled true undefined
javascript.options.legacy_tosource_lookup undefined false
javascript.options.wasm_stack_switching undefined false
layout.abspos.fragmentainer-aware-positioning.enabled false true
layout.css.fake-webkit-scrollbar.enabled undefined false
layout.css.marker.restricted true undefined
layout.css.style-queries.enabled false true
layout.css.video-dynamic-range.allows-high true undefined
mathml.href_link_on_non_anchor_element.disabled undefined false
mathml.math_shift.enabled true undefined
mathml.rtl_operator_mirroring.enabled true undefined
media.getusermedia.audio.processing.aec.mobile false undefined
media.gmp-manager.cert.checkAttributes true undefined
media.gmp-manager.certs.1.commonName aus5.mozilla.org undefined
media.gmp-manager.certs.1.issuerName CN=DigiCert SHA2 Secure Server CA,O=DigiCert Inc,C=US undefined
media.gmp-manager.certs.2.commonName aus5.mozilla.org undefined
media.gmp-manager.certs.2.issuerName CN=thawte SSL CA - G2,O="thawte, Inc.",C=US undefined
memory.reporter.timeout undefined 180000
network.auth.supress_auth_prompt_for_XFO_failures true undefined
network.cookie.validation.epoch undefined 1
network.cookie.validation.lastEpoch undefined 0
network.http.origin.useTriggeringPrincipal undefined true
network.http.rcwn.cache_queue_normal_threshold 8 undefined
network.http.rcwn.cache_queue_priority_threshold 2 undefined
network.http.rcwn.enabled false undefined
network.http.rcwn.max_wait_before_racing_ms 500 undefined
network.http.rcwn.min_wait_before_racing_ms 0 undefined
network.http.rcwn.race_with_non_ssd false undefined
network.http.rcwn.small_resource_size_kb 256 undefined
network.lna.defer_https_check undefined true
network.proxy.fast_path_system_direct undefined true
network.ssl_tokens_cache_capacity 2048 8192
network.trr.preconnect_on_foreground undefined true
network.trr.preserve_on_background undefined false
nimbus.firstUpdateComplete undefined false
pdfjs.enableMerge undefined true
places.frecency.bookmarkVisitBonus 75 undefined
places.frecency.defaultBucketWeight 10 undefined
places.frecency.defaultVisitBonus 0 undefined
places.frecency.downloadVisitBonus 0 undefined
places.frecency.embedVisitBonus 0 undefined
places.frecency.firstBucketCutoff 4 undefined
places.frecency.firstBucketWeight 100 undefined
places.frecency.fourthBucketCutoff 90 undefined
places.frecency.fourthBucketWeight 30 undefined
places.frecency.framedLinkVisitBonus 0 undefined
places.frecency.linkVisitBonus 100 undefined
places.frecency.numVisits 10 undefined
places.frecency.permRedirectVisitBonus 50 undefined
places.frecency.redirectSourceVisitBonus 25 undefined
places.frecency.reloadVisitBonus 0 undefined
places.frecency.secondBucketCutoff 14 undefined
places.frecency.secondBucketWeight 70 undefined
places.frecency.tempRedirectVisitBonus 40 undefined
places.frecency.thirdBucketCutoff 31 undefined
places.frecency.thirdBucketWeight 50 undefined
places.frecency.typedVisitBonus 2000 undefined
places.frecency.unvisitedBookmarkBonus 140 undefined
places.frecency.unvisitedTypedBonus 200 undefined
privacy.bounceTrackingProtection.requireStatefulBounces false undefined
privacy.partition.network_state true undefined
privacy.partition.network_state.ocsp_cache true undefined
privacy.partition.network_state.ocsp_cache.pbmode true undefined
services.sync.prefs.sync.browser.ipProtection.enabled true undefined
sidebar.updatedBookmarks.enabled undefined false
signon.rustMirror.collectFailedOrigins undefined false
toolkit.telemetry.enabled false true