This is difference between the default preference of Firefox 125.0 beta 6 and one of 124.0.1. This diff table is generated with my small script firefox-prefjs-surveyer.

Preference difference
PrefFirefox 124.0.1Firefox 125.0 beta 6
accessibility.ARIAElementReflection.enabled undefined false
accessibility.ARIAReflection.enabled true undefined
accessibility.uia.enable undefined false
accessibility.windows.suppress-for-snap-layout undefined 2
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.backup.enabled undefined false
browser.contentanalysis.agent_name undefined A DLP agent
browser.contentanalysis.agent_timeout undefined 30
browser.contentanalysis.allow_url_regex_list undefined
browser.contentanalysis.client_signature undefined
browser.contentanalysis.deny_url_regex_list undefined
browser.contentanalysis.show_blocked_result undefined true
browser.contentblocking.reportBreakage.url https://tracking-protection-issues.herokuapp.com/new undefined
browser.device-migration.help-menu.hidden false undefined
browser.mailto.dualPrompt.os false undefined
browser.ml.enable undefined false
browser.ml.logLevel undefined Error
browser.newtabpage.activity-stream.discoverystream.spocMessageVariant undefined
browser.newtabpage.activity-stream.telemetry.ut.events false true
browser.profiles.enabled undefined false
browser.sessionstore.collect_session_storage true undefined
browser.sessionstore.collect_zoom true undefined
browser.sessionstore.disable_platform_collection undefined false
browser.sessionstore.platform_collection true undefined
browser.tabs.cardPreview.delayMs 1000 undefined
browser.toolbars.bookmarks.showInPrivateBrowsing false undefined
browser.urlbar.clipboard.featureGate false true
browser.urlbar.quickactions.enabled undefined true
browser.urlbar.quickactions.showPrefs undefined true
browser.urlbar.shortcuts.quickactions undefined true
browser.urlbar.showSearchTerms.featureGate false true
browser.urlbar.suggest.quickactions undefined true
browser.urlbar.switchTabs.searchAllContainers false true
browser.urlbar.trending.featureGate undefined true
cookiebanners.ui.desktop.enabled false true
devtools.debugger.features.overlay undefined true
devtools.performance.recording.markers.external-url undefined
dom.disable_tab_focus_to_root_element undefined false
dom.document.edit_command.contentReadOnly.enabled true false
dom.document.edit_command.insertBrOnReturn.enabled true false
dom.domrequest.enabled false undefined
dom.element.popover.enabled false true
dom.event.keypress.key.allow_lone_surrogate true false
dom.events.asyncClipboard.clipboardItem false true
dom.events.asyncClipboard.readText false true
dom.events.mouse-pointer-boundary.keep-enter-targets-after-over-target-removed false true
dom.forms.always_allow_key_and_focus_events.enabled false true
dom.forms.fieldset_disable_only_descendants.enabled false true
dom.forms.number.hide_spin_buttons_when_no_hover_or_focus undefined false
dom.indexedDB.connectionIdleMaintenance.pauseOnConnectionThreadMs undefined 0
dom.media.webcodecs.force-osx-h264-enabled false undefined
dom.navigation.object_embed.allow_retargeting undefined false
dom.screenwakelock.enabled false true
dom.security.https_first_schemeless false true
dom.security.setdocumenturi false true
dom.security.trusted_types.enabled undefined false
extensions.InstallTrigger.enabled true false
extensions.formautofill.addresses.capture.enabled false true
extensions.webcompat-reporter.enabled false true
fission.enforceBlocklistedPrefsInSubprocesses false true
gfx.canvas.remote.allow-offscreen undefined true
gfx.offscreencanvas.snapshot-timeout-ms undefined 10000
gfx.webrender.overlay-vp-auto-hdr undefined false
gfx.webrender.overlay-vp-super-resolution undefined false
gfx.webrender.super-resolution.nvidia false undefined
javascript.options.mem.nursery_eager_collection_threshold_kb undefined 256
javascript.options.mem.nursery_eager_collection_threshold_percent undefined 25
javascript.options.mem.nursery_eager_collection_timeout_ms undefined 5000
javascript.options.use_fdlibm_for_sin_cos_tan false true
javascript.options.wasm_exceptions true undefined
javascript.options.wasm_exnref false true
javascript.options.wasm_extended_const true undefined
javascript.options.wasm_function_references true undefined
javascript.options.wasm_js_string_builtins undefined false
javascript.options.wasm_memory64 undefined false
javascript.options.wasm_memory_control undefined false
javascript.options.wasm_multi_memory undefined true
javascript.options.wasm_relaxed_simd undefined false
javascript.options.wasm_test_serialization undefined false
layout.css.align-content.blocks.enabled undefined true
layout.css.content-visibility.enabled false true
layout.css.h1-in-section-ua-styles.enabled undefined true
layout.css.math-depth.enabled true undefined
layout.css.math-style.enabled true undefined
layout.css.scroll-anchoring.absolute-update true undefined
layout.css.transform-box-content-stroke.enabled false true
layout.css.transition-behavior.enabled undefined false
layout.dynamic-reflow-roots.enabled false true
media.ffvpx.enabled true undefined
media.peerconnection.description.legacy.enabled undefined true
media.peerconnection.treat_warnings_as_errors undefined false
memory.phc.enabled false true
network.auth.use_redirect_for_retries false true
network.cache.purge_minprogress_disk undefined 0
network.cache.purge_minprogress_memory undefined 32
network.cache.purgebyfrecency_minprogress_disk 0 undefined
network.cache.purgebyfrecency_minprogress_memory 0 undefined
network.cookie.sameSite.noneRequiresSecure false true
network.dns.native_https_query false true
network.fetchpriority.adjustments.async-or-defer-script.auto undefined 0
network.fetchpriority.adjustments.async-or-defer-script.high undefined -10
network.fetchpriority.adjustments.async-or-defer-script.low undefined 10
network.fetchpriority.adjustments.deferred-style.auto undefined 0
network.fetchpriority.adjustments.deferred-style.high undefined 0
network.fetchpriority.adjustments.deferred-style.low undefined 10
network.fetchpriority.adjustments.global-fetch-api.auto undefined 0
network.fetchpriority.adjustments.global-fetch-api.high undefined -10
network.fetchpriority.adjustments.global-fetch-api.low undefined 10
network.fetchpriority.adjustments.images.auto undefined 0
network.fetchpriority.adjustments.images.high undefined -20
network.fetchpriority.adjustments.images.low undefined 0
network.fetchpriority.adjustments.link-preload-fetch.auto undefined 0
network.fetchpriority.adjustments.link-preload-fetch.high undefined -10
network.fetchpriority.adjustments.link-preload-fetch.low undefined 10
network.fetchpriority.adjustments.link-preload-font.auto undefined 0
network.fetchpriority.adjustments.link-preload-font.high undefined 0
network.fetchpriority.adjustments.link-preload-font.low undefined 20
network.fetchpriority.adjustments.link-preload-script.auto undefined 0
network.fetchpriority.adjustments.link-preload-script.high undefined 0
network.fetchpriority.adjustments.link-preload-script.low undefined 30
network.fetchpriority.adjustments.link-preload-style.auto undefined 0
network.fetchpriority.adjustments.link-preload-style.high undefined 0
network.fetchpriority.adjustments.link-preload-style.low undefined 10
network.fetchpriority.adjustments.module-script.auto undefined 0
network.fetchpriority.adjustments.module-script.high undefined -10
network.fetchpriority.adjustments.module-script.low undefined 10
network.fetchpriority.adjustments.non-deferred-style.auto undefined 0
network.fetchpriority.adjustments.non-deferred-style.high undefined -20
network.fetchpriority.adjustments.non-deferred-style.low undefined 0
network.fetchpriority.adjustments.other-script.auto undefined 0
network.fetchpriority.adjustments.other-script.high undefined -10
network.fetchpriority.adjustments.other-script.low undefined 10
network.fetchpriority.adjustments.script-in-head.auto undefined 0
network.fetchpriority.adjustments.script-in-head.high undefined -10
network.fetchpriority.adjustments.script-in-head.low undefined 10
network.http.http3.retry_different_ip_family false true
network.jar.max_entry_size undefined 268435456
network.jar.record_failure_reason false true
network.predictor.enable-prefetch false true
network.protocol-handler.external.firefox false undefined
network.protocol-handler.external.firefox-bridge undefined false
network.protocol-handler.external.firefox-private false undefined
network.protocol-handler.external.firefox-private-bridge undefined false
network.proxy.system_wpad undefined false
network.proxy.system_wpad.allowed undefined false
network.send_OnDataFinished.cssLoader undefined true
pdfjs.enableHighlightEditor false true
pdfjs.enableHighlightFloatingButton undefined false
plugins.rewrite_youtube_embeds true false
privacy.annotate_channels.strict_list.enabled false true
privacy.clearHistory.cache undefined true
privacy.clearHistory.cookiesAndStorage undefined true
privacy.clearHistory.historyFormDataAndDownloads undefined true
privacy.clearHistory.siteSettings undefined false
privacy.clearSiteData.cache undefined true
privacy.clearSiteData.cookiesAndStorage undefined true
privacy.clearSiteData.historyFormDataAndDownloads undefined false
privacy.clearSiteData.siteSettings undefined false
privacy.sanitize.clearOnShutdown.hasMigratedToNewPrefs undefined false
privacy.sanitize.cpd.hasMigratedToNewPrefs undefined false
privacy.sanitize.sanitizeOnShutdown.hasMigratedToNewPrefs false undefined
security.disallow_non_local_systemprincipal_in_tests undefined false
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.companion undefined false
startup.homepage_override_nimbus_maxVersion undefined
startup.homepage_override_url_nimbus undefined
svg.SVGAElement.text.enabled undefined false
svg.nearestAndFarthestViewportElement.enabled true false
toolkit.telemetry.enabled false true
toolkit.telemetry.user_characteristics_ping.current_version undefined 0
toolkit.telemetry.user_characteristics_ping.last_version_sent undefined 0
toolkit.telemetry.user_characteristics_ping.uuid undefined
ui.new-webcompat-reporter.send-more-info-link false true
ui.tooltip.delay_ms undefined 500
ui.touch_activation.duration_ms 10 50
widget.gtk.global-menu.enabled undefined false
widget.gtk.global-menu.wayland.enabled undefined false
widget.gtk.legacy-cursors.enabled undefined false
widget.gtk.middle-click-enabled undefined true
widget.gtk.non-native-titlebar-buttons.enabled undefined true