This is difference between the default preference of Firefox 116.0 beta 8 and one of 115.0.2. This diff table is generated with my small script firefox-prefjs-surveyer.

Preference difference
PrefFirefox 116.0.2Firefox 116.0 beta 8
accessibility.usetexttospeech undefined
app.releaseNotesURL https://www.mozilla.org/%LOCALE%/firefox/%VERSION%/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-browser&utm_campaign=whatsnew https://www.mozilla.org/%LOCALE%/firefox/%VERSION%beta/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-browser&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.releaseNotesURL.prompt undefined https://www.mozilla.org/%LOCALE%/firefox/%VERSION%/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-browser&utm_campaign=updateprompt
app.update.channel release beta
app.update.download.maxAttempts undefined 2
app.update.download.promptMaxAttempts 2 undefined
app.update.elevate.maxAttempts undefined 2
app.update.elevation.promptMaxAttempts 2 undefined
app.update.link.updateAvailableWhatsNew update-available-whats-new undefined
app.update.link.updateManualWhatsNew update-manual-whats-new undefined
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.offline.capacity 512000 undefined
browser.chrome.errorReporter.infoURL https://support.mozilla.org/1/firefox/%VERSION%/%OS%/%LOCALE%/nightly-error-collection undefined
browser.chrome.image_icons.max_size 1024 undefined
browser.migrate.chrome.extensions.enabled undefined false
browser.migrate.interactions.csvpasswords undefined false
browser.protections_panel.infoMessage.seen undefined false
browser.search.hiddenOneOffs undefined
browser.shopping.experience2023.enabled undefined false
browser.tabs.firefox-view-next undefined false
browser.translation.detectLanguage false undefined
browser.translation.engine Google undefined
browser.translation.ui.show false undefined
browser.translations.automaticallyPopup undefined true
browser.translations.languageIdentification.useFastText undefined false
browser.urlbar.pocket.featureGate undefined false
browser.urlbar.suggest.pocket undefined true
device.storage.enabled false undefined
devtools.custom-formatters false undefined
devtools.debugger.features.command-click false undefined
devtools.debugger.features.component-pane false undefined
devtools.remote.wifi.scan true undefined
docshell.shistory.bfcache.ship_allow_beforeunload_listeners false true
dom.abort_script_on_child_shutdown false true
dom.clients.openwindow_favors_same_process true undefined
dom.event.wheel-event-groups.enabled false true
dom.events.dataTransfer.mozFile.enabled false true
dom.events.phases.correctOrderOnTarget undefined false
dom.forms.fieldset_disable_only_descendants.enabled undefined false
dom.ipc.plugins.allow_dxgi_surface true undefined
dom.ipc.plugins.asyncdrawing.enabled true undefined
dom.ipc.plugins.contentTimeoutSecs 10 undefined
dom.ipc.plugins.forcedirect.enabled true undefined
dom.ipc.plugins.parentTimeoutSecs 0 undefined
dom.ipc.plugins.processLaunchTimeoutSecs 45 undefined
dom.ipc.plugins.reportCrashURL true undefined
dom.ipc.plugins.timeoutSecs 45 undefined
dom.ipc.plugins.unloadTimeoutSecs 30 undefined
dom.ipc.tabs.disabled false undefined
dom.payments.defaults.saveAddress true undefined
dom.payments.defaults.saveCreditCard false undefined
dom.payments.loglevel Warn undefined
dom.performance.children_results_ipc_timeout 1000 undefined
dom.storage_access.frame_only undefined true
dom.textMetrics.baselines.enabled false true
dom.textMetrics.fontBoundingBox.enabled false true
dom.wakelock.enabled false undefined
dom.window_position_size_properties_replaceable.enabled true undefined
dom.workers.GCCC_on_potentially_last_event undefined false
extensions.checkCompatibility.temporaryThemeOverride_minAppVersion 29.0a1 undefined
extensions.getAddons.browserMappings.url undefined https://services.addons.mozilla.org/api/v5/addons/browser-mappings/?browser=%BROWSER%
extensions.pocket.onSaveRecs true undefined
extensions.pocket.onSaveRecs.locales en-US,en-GB,en-CA undefined
extensions.webcompat-reporter.enabled false true
extensions.webextensions.enablePerformanceCounters true undefined
extensions.webextensions.performanceCountersMaxAge 5000 undefined
gfx.allow-texture-direct-mapping true undefined
gfx.canvas.accelerated.max-draw-target-count undefined 200
gfx.direct2d.destroy-dt-on-paintthread true undefined
gfx.draw-color-bars false undefined
gfx.e10s.hide-plugins-for-scroll true undefined
gfx.vsync.collect-scroll-transforms false undefined
gfx.webrender.enable-subpixel-aa undefined true
identity.fxaccounts.commands.enabled true undefined
identity.fxaccounts.service.monitorLoginUrl https://monitor.firefox.com/ undefined
image.mem.animated.use_heap false undefined
image.mem.volatile.min_threshold_kb -1 undefined
image.multithreaded_decoding.idle_timeout 600000 undefined
image.multithreaded_decoding.limit -1 undefined
intl.fallbackCharsetList.ISO-8859-1 windows-1252 undefined
javascript.options.content_process_write_protect_code undefined false
layout.css.abs-sign.enabled undefined false
layout.css.font-synthesis-small-caps.enabled true undefined
layout.css.font-visibility.resistFingerprinting 1 undefined
layout.css.gradient-color-interpolation-method.enabled undefined false
layout.css.inline-style-caching.always-enabled undefined true
layout.css.motion-path-basic-shapes.enabled undefined false
layout.css.motion-path-coord-box.enabled undefined false
layout.css.nth-child-of.enabled true undefined
layout.css.stylo-local-work-queue.in-main-thread undefined 32
layout.css.stylo-local-work-queue.in-worker undefined 0
layout.css.stylo-parallelism-threshold 32 undefined
layout.display-list.flatten-transform true undefined
layout.min-active-layer-size 64 undefined
media.aboutwebrtc.auto_refresh undefined true
media.allow-audio-non-utility undefined true
media.audio.device.retry.ms undefined 1000
media.cubeb.logging_level undefined
media.getdisplaymedia.previews.enabled undefined true
media.gmp.decoder.aac 0 undefined
media.gmp.decoder.h264 0 undefined
media.gmp.trial-create.enabled true undefined
media.omt_data_delivery.enabled true undefined
media.peerconnection.video.enabled true undefined
media.setsinkid.enabled false true
media.throttle-regardless-of-download-rate false undefined
media.videocontrols.picture-in-picture.respect-disablePictureInPicture false true
media.webrtc.camera.allow-pipewire undefined false
media.webrtc.debug.multi_log false undefined
media.webrtc.debug.trace_mask 0 undefined
network.cache.frecency_array_check_enabled false undefined
network.compress.allow_truncated_empty_brotli undefined true
network.http.http2.persistent-settings false undefined
network.http.http3.block_loopback_ipv6_addr undefined false
network.http.http3.retry_different_ip_family undefined true
network.http.useragent.forceVersion 0 undefined
network.jar.require_size_match undefined true
network.mdns.use_js_fallback false undefined
network.trr.add_additional_records undefined true
nglayout.debug.widget_update_flashing false undefined
pdfjs.firstRun true undefined
plugin.override_internal_types false undefined
plugins.navigator.hidden_ctp_plugin undefined
plugins.show_infobar false undefined
plugins.testmode false undefined
privacy.fuzzyfox.clockgrainus 100 undefined
privacy.item.cookies false undefined
privacy.popups.disable_from_plugins 3 undefined
privacy.popups.policy 1 undefined
privacy.popups.usecustom true undefined
privacy.resistFingerprinting.randomization.enabled false undefined
privacy.resistFingerprinting.testGranularityMask 0 undefined
privacy.resistFingerprinting.testing.setTZtoUTC false undefined
privacy.sanitize.migrateFx3Prefs false undefined
privacy.webrtc.allowSilencingNotifications false true
privacy.webrtc.hideGlobalIndicator undefined false
privacy.webrtc.legacyGlobalIndicator true false
profile.manage_only_at_launch false undefined
reader.has_used_toolbar false undefined
security.csp.external-hashes.enabled undefined true
security.identitypopup.recordEventTelemetry true undefined
threads.medium_high_event_queue.enabled true undefined
timer.maximum_firing_delay_tolerance_ms 0.0 10000.0
toolkit.aboutPerformance.showInternals false undefined
toolkit.telemetry.enabled false true
trailhead.firstrun.newtab.triplets undefined
webgl.out-of-process.async-present.force-sync true false
widget.clipboard.use-cached-data.enabled undefined false
widget.pause-compositor-when-minimized true undefined
xpinstall.signatures.devInfoURL https://wiki.mozilla.org/Addons/Extension_Signing undefined