hello, could you go to the firefox menu ≡ > help ? > troubleshooting information, copy the contents of that page and paste them here into a reply on the forum? this might give us a clue what is going on...

Application Basics Name Firefox Version 50.0 Build ID 20161104212021 Update History Show Update History Update Channel release-cck-mozilla18 User Agent Mozilla/5.0 (Windows NT 6.1; WOW64; rv:50.0) Gecko/20100101 Firefox/50.0 OS Windows_NT 6.1 Profile Folder Show Folder Enabled Plugins about:plugins

Build Configuration about:buildconfig

Memory Use about:memory

Performance about:performance

Registered Service Workers about:serviceworkers

Multiprocess Windows 1/1 (Enabled by default) Safe Mode false Profiles about:profiles

Crash Reports for the Last 3 Days Report ID Submitted All Crash Reports (including 4 pending crashes in the given time range) This application has not been configured to display crash reports. Extensions Name Version Enabled ID Adblock Plus 2.8.2 true {d10d0bf8-f5b5-c8b4-a8b2-2b9879e08c5d} Application Update Service Helper 1.0 true [email protected] Complete YouTube Saver 5.7.26 true {AF445D67-154C-4c69-A17B-7F392BCC36A3} Multi-process staged rollout 1.5 true [email protected] Pocket 1.0.5 true [email protected] uBlock Origin 1.9.16 true [email protected] Web Compat 1.0 true [email protected] HP Smart Web Printing 4.60 false [email protected] Graphics Features Compositing Direct3D 11 Asynchronous Pan/Zoom wheel input enabled WebGL Renderer Google Inc. -- ANGLE (Intel(R) HD Graphics Family Direct3D11 vs_4_1 ps_4_1) WebGL2 Renderer (no info) Hardware H264 Decoding Yes; Using D3D9 API Audio Backend wasapi Direct2D true DirectWrite true (6.2.9200.21976) GPU #1 Active Yes Description Intel(R) HD Graphics Family Vendor ID 0x8086 Device ID 0x0126 Driver Version 8.15.10.2622 Driver Date 1-10-2012 Drivers igdumd64 igd10umd64 igd10umd64 igdumdx32 igd10umd32 igd10umd32 Subsys ID 00000000 RAM Unknown

Diagnostics AzureCanvasAccelerated 0 AzureCanvasBackend direct2d 1.1 AzureContentBackend direct2d 1.1 AzureFallbackCanvasBackend cairo Decision Log D3D9_COMPOSITING disabled by default: Disabled by default

Important Modified Preferences Name Value accessibility.typeaheadfind.flashBar 0 browser.cache.disk.capacity 358400 browser.cache.disk.filesystem_reported 1 browser.cache.disk.hashstats_reported 1 browser.cache.disk.smart_size_cached_value 358400 browser.cache.disk.smart_size.first_run false browser.cache.disk.smart_size.use_old_max false browser.cache.frecency_experiment 4 browser.download.importedFromSqlite true browser.download.manager.alertOnEXEOpen true browser.places.smartBookmarksVersion 8 browser.search.param.yahoo-fr chr-greentree_ff&ilc=12&type=714647 browser.search.useDBForOrder true browser.sessionstore.upgradeBackup.latestBuildID 20161104212021 browser.startup.homepage https://www.yahoo.com/?fr=fptb-tyc-sc browser.startup.homepage_override.buildID 20161104212021 browser.startup.homepage_override.mstone 50.0 browser.tabs.remote.autostart.2 true browser.urlbar.default.behavior 1 browser.urlbar.suggest.bookmark false browser.urlbar.suggest.openpage false browser.urlbar.suggest.searches true browser.urlbar.userMadeSearchSuggestionsChoice true dom.apps.lastUpdate.buildID 20161019084923 dom.apps.lastUpdate.mstone 49.0.2 dom.apps.reset-permissions true dom.mozApps.used true dom.push.userAgentID ea7a0f6bcbbb40b9b91fc8adfe95b28b dom.w3c_touch_events.expose false extensions.lastAppVersion 50.0 gfx.crash-guard.d3d11layers.appVersion 50.0 gfx.crash-guard.d3d11layers.deviceID 0x0126 gfx.crash-guard.d3d11layers.driverVersion 8.15.10.2622 gfx.crash-guard.d3d11layers.feature-d2d true gfx.crash-guard.d3d11layers.feature-d3d11 true gfx.crash-guard.glcontext.gfx.driver-init.direct3d11-angle true gfx.crash-guard.glcontext.gfx.driver-init.webgl-angle true gfx.crash-guard.glcontext.gfx.driver-init.webgl-angle-force-d3d11 false gfx.crash-guard.glcontext.gfx.driver-init.webgl-angle-force-warp false gfx.crash-guard.glcontext.gfx.driver-init.webgl-angle-try-d3d11 true gfx.crash-guard.status.d3d11layers 2 gfx.crash-guard.status.d3d9video 2 gfx.crash-guard.status.glcontext 2 gfx.direct3d.last_used_feature_level_idx 0 gfx.direct3d.prefer_10_1 true gfx.driver-init.appVersion 42.0 gfx.driver-init.deviceID 0x0126 gfx.driver-init.driverVersion 8.15.10.2622 gfx.driver-init.feature-d2d true gfx.driver-init.feature-d3d11 true gfx.driver-init.status 2 media.benchmark.vp9.fps 125 media.benchmark.vp9.versioncheck 1 media.gmp-eme-adobe.abi x86-msvc-x64 media.gmp-eme-adobe.lastUpdate 1461774449 media.gmp-eme-adobe.version 17 media.gmp-gmpopenh264.abi x86-msvc-x64 media.gmp-gmpopenh264.lastUpdate 1471456588 media.gmp-gmpopenh264.version 1.6 media.gmp-manager.buildID 20161104212021 media.gmp-manager.lastCheck 1480006771 media.gmp-widevinecdm.abi x86-msvc-x64 media.gmp-widevinecdm.lastUpdate 1474772766 media.gmp-widevinecdm.version 1.4.8.903 media.gmp.storage.version.observed 1 media.hardware-video-decoding.failed false media.mediasource.webm.enabled true media.webrtc.debug.aec_log_dir C:\Users\Joe\AppData\Local\Temp media.webrtc.debug.log_file C:\Users\Joe\AppData\Local\Temp\WebRTC.log network.auth.allow-subresource-auth 2 network.cookie.prefsMigrated true network.dns.disablePrefetch true network.http.speculative-parallel-limit 0 network.predictor.cleaned-up true network.prefetch-next false places.database.lastMaintenance 1479788887 places.history.expiration.transient_current_max_pages 88989 plugin.disable_full_page_plugin_for_types application/pdf plugin.importedState true plugin.state.npdeployjava 0 plugin.state.npvlc 2 print.printer_HP_Officejet_Pro_K8600_Series.print_bgcolor false print.printer_HP_Officejet_Pro_K8600_Series.print_bgimages false print.printer_HP_Officejet_Pro_K8600_Series.print_duplex -1220153466 print.printer_HP_Officejet_Pro_K8600_Series.print_edge_bottom 0 print.printer_HP_Officejet_Pro_K8600_Series.print_edge_left 0 print.printer_HP_Officejet_Pro_K8600_Series.print_edge_right 0 print.printer_HP_Officejet_Pro_K8600_Series.print_edge_top 0 print.printer_HP_Officejet_Pro_K8600_Series.print_evenpages true print.printer_HP_Officejet_Pro_K8600_Series.print_footercenter print.printer_HP_Officejet_Pro_K8600_Series.print_footerleft &PT print.printer_HP_Officejet_Pro_K8600_Series.print_footerright &D print.printer_HP_Officejet_Pro_K8600_Series.print_headercenter print.printer_HP_Officejet_Pro_K8600_Series.print_headerleft &T print.printer_HP_Officejet_Pro_K8600_Series.print_headerright &U print.printer_HP_Officejet_Pro_K8600_Series.print_in_color true print.printer_HP_Officejet_Pro_K8600_Series.print_margin_bottom 0.5 print.printer_HP_Officejet_Pro_K8600_Series.print_margin_left 0.5 print.printer_HP_Officejet_Pro_K8600_Series.print_margin_right 0.5 print.printer_HP_Officejet_Pro_K8600_Series.print_margin_top 0 print.printer_HP_Officejet_Pro_K8600_Series.print_oddpages true print.printer_HP_Officejet_Pro_K8600_Series.print_orientation 1 print.printer_HP_Officejet_Pro_K8600_Series.print_page_delay 50 print.printer_HP_Officejet_Pro_K8600_Series.print_paper_data -1 print.printer_HP_Officejet_Pro_K8600_Series.print_paper_height 11.00 print.printer_HP_Officejet_Pro_K8600_Series.print_paper_name print.printer_HP_Officejet_Pro_K8600_Series.print_paper_size_unit 0 print.printer_HP_Officejet_Pro_K8600_Series.print_paper_width 8.50 print.printer_HP_Officejet_Pro_K8600_Series.print_resolution 600 print.printer_HP_Officejet_Pro_K8600_Series.print_reversed false print.printer_HP_Officejet_Pro_K8600_Series.print_scaling 1.00 print.printer_HP_Officejet_Pro_K8600_Series.print_shrink_to_fit true print.printer_HP_Officejet_Pro_K8600_Series.print_to_file false print.printer_HP_Officejet_Pro_K8600_Series.print_unwriteable_margin_bottom 0 print.printer_HP_Officejet_Pro_K8600_Series.print_unwriteable_margin_left 0 print.printer_HP_Officejet_Pro_K8600_Series.print_unwriteable_margin_right 0 print.printer_HP_Officejet_Pro_K8600_Series.print_unwriteable_margin_top 0 print.printer_HP_Photosmart_D110_series.print_bgcolor false print.printer_HP_Photosmart_D110_series.print_bgimages false print.printer_HP_Photosmart_D110_series.print_colorspace print.printer_HP_Photosmart_D110_series.print_command print.printer_HP_Photosmart_D110_series.print_downloadfonts false print.printer_HP_Photosmart_D110_series.print_duplex -1220153466 print.printer_HP_Photosmart_D110_series.print_edge_bottom 0 print.printer_HP_Photosmart_D110_series.print_edge_left 0 print.printer_HP_Photosmart_D110_series.print_edge_right 0 print.printer_HP_Photosmart_D110_series.print_edge_top 0 print.printer_HP_Photosmart_D110_series.print_evenpages true print.printer_HP_Photosmart_D110_series.print_footercenter print.printer_HP_Photosmart_D110_series.print_footerleft &PT print.printer_HP_Photosmart_D110_series.print_footerright &D print.printer_HP_Photosmart_D110_series.print_headercenter print.printer_HP_Photosmart_D110_series.print_headerleft &T print.printer_HP_Photosmart_D110_series.print_headerright &U print.printer_HP_Photosmart_D110_series.print_in_color true print.printer_HP_Photosmart_D110_series.print_margin_bottom 0.5 print.printer_HP_Photosmart_D110_series.print_margin_left 0.5 print.printer_HP_Photosmart_D110_series.print_margin_right 0.5 print.printer_HP_Photosmart_D110_series.print_margin_top 0 print.printer_HP_Photosmart_D110_series.print_oddpages true print.printer_HP_Photosmart_D110_series.print_orientation 1 print.printer_HP_Photosmart_D110_series.print_page_delay 50 print.printer_HP_Photosmart_D110_series.print_paper_data 1 print.printer_HP_Photosmart_D110_series.print_paper_height 11.00 print.printer_HP_Photosmart_D110_series.print_paper_name print.printer_HP_Photosmart_D110_series.print_paper_size_type 0

print.printer_HP_Photosmart_D110_series.print_paper_size_unit 0 print.printer_HP_Photosmart_D110_series.print_paper_width 8.50 print.printer_HP_Photosmart_D110_series.print_plex_name print.printer_HP_Photosmart_D110_series.print_resolution 127688224 print.printer_HP_Photosmart_D110_series.print_resolution_name print.printer_HP_Photosmart_D110_series.print_reversed false print.printer_HP_Photosmart_D110_series.print_scaling 1.00 print.printer_HP_Photosmart_D110_series.print_shrink_to_fit true print.printer_HP_Photosmart_D110_series.print_to_file false print.printer_HP_Photosmart_D110_series.print_unwriteable_margin_bottom 0 print.printer_HP_Photosmart_D110_series.print_unwriteable_margin_left 0 print.printer_HP_Photosmart_D110_series.print_unwriteable_margin_right 0 print.printer_HP_Photosmart_D110_series.print_unwriteable_margin_top 0 privacy.cpd.cookies false privacy.cpd.downloads false privacy.cpd.formdata false privacy.cpd.history false privacy.cpd.sessions false privacy.sanitize.migrateClearSavedPwdsOnExit true privacy.sanitize.migrateFx3Prefs true privacy.sanitize.timeSpan 0 security.mixed_content.block_active_content false security.sandbox.content.tempDirSuffix {7b6b03d9-beb3-4559-8e43-1a66d1c8c034} security.warn_viewing_mixed false services.sync.declinedEngines tabs services.sync.engine.prefs.modified false services.sync.engine.tabs false services.sync.lastPing 1480059555 services.sync.lastSync Fri Nov 25 2016 04:18:47 GMT-0500 (Eastern Standard Time) services.sync.numClients 1 storage.vacuum.last.index 1 storage.vacuum.last.places.sqlite 1479195089 user.js Preferences Your profile folder contains a user.js file, which includes preferences that were not created by Firefox. Important Locked Preferences Name Value Places Database Integrity Verify Integrity JavaScript Incremental GC true Accessibility Activated false Prevent Accessibility 0 Library Versions Expected minimum version Version in use NSPR 4.12 4.12 NSS 3.26.2 3.26.2 NSSSMIME 3.26.2 3.26.2 NSSSSL 3.26.2 3.26.2 NSSUTIL 3.26.2 3.26.2 Experimental Features Name ID Description Active End Date Homepage Branch Sandbox Content Process Sandbox Level 1

thanks, it's not a good idea to run adblock plus and ublock origin at the same time - please try to disable or remove adblock plus and see if this is already making a difference.

also, there appears to be a user.js file present in your profile, which (unless you have manually and intentionally created yourself) is usually a sign of malicious activity on a device. go to the firefox menu ≡ > (?) help > troubleshooting information page and click on the button to open the profile folder. an explorer window should open up - in there look out for the file named user.js and delete it. afterwards, run a full scan of your system with different security tools like the free version of malwarebytes & adwcleaner, which are specialised in adware and browser hijackers.

I've removed Adblock Plus (had been meaning to do so for some time, just had left it in while I was first trying ublock origin out and kept forgetting to do so) and also used malwarebytes and adwcleaner to remove all PUPs on my computer.

The result is that initial memory use by FireFox is now much lower (around 200,000 kb for each process), but the number for one process (the tabs) continues to gradually increase the longer I keep it open, albeit at a much slower pace. It took around a day to climb to 700,000 kb, and it still doesn't ever decrease unless I close and reopen Firefox.

So presumably if I just leave it open it'll eventually reach a point where it will slow down considerably again.