View source for Thunderbird:Testing:Memory Usage Problems

__TOC__
'''This article is for users with ALL types of performance issues.'''

Thunderbird performance (slowness) can be affected by CPU, memory and disk activity from many sources. You are likely frustrated, so the steps are simplified to be clear and easy to follow. '''Please step through the full list below to have the best possible chance of success.'''  

= Diagnosis =
== Before starting ==
* '''Many steps are <u>temporary</u> *tests*, not a request for you to forever disable a feature.''' Disabling antivirus software for example. 
* '''Do not delete files'''. Instead, rename or move files because we may need "bad files" later for developers to examine.
* As you go through the steps, collect the information you will need to later report a problem:
** When referring to memory, cpu, amount of time, numbers of folders and messages, etc, <u>provide numbers</u> for quantities, not vague words like fast/slow, small/large.
** List <u>account types</u> (imap, pop, rss, etc) from Help | More Troubleshooting Info.
** Provide full Thunderbird <u>version number</u> from Help | About.
** State precisely <u>when</u> the behavior occurs (startup, shutdown, or "normal operation"), and <u>every step</u> (action, menu click, ...) needed to reproduce the problem.
** Cite the step numbers of this document that you tested, and any which helped or didn't help improved your issue. Also [[Thunderbird:Testing:Memory_Usage_Problems#References|bug numbers]], URLs of postings and references you used.
** Whether your [https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data Thunderbird profile data] is in a non-standard location.
** Screen shots can be helpful.

== Diagnosis Steps ==

# Are you using the newest Thunderbird? <small>(Versions are listed at [https://www.thunderbird.net/en-US/thunderbird/releases/ releases]. The newest version there should match to your Help | About.  If check for Updates doesn't get you to that version, then download it from [https://www.thunderbird.net/ thunderbird.net].</small>)
#Start Thunderbird in [https://support.mozilla.org/kb/troubleshoot-mode-thunderbird Troubleshoot Mode]. If Troubleshoot Mode helped, then start in normal mode. If the problem returned:
#*Visit Tools | Add-ons - disable two or more add-ons at a time (or themes or language packs) to determine which might be causing the problem. Are any Add-on items in the [[#Other_Software|list of Problem Extensions]]?  
#*Contact the '''author''' of suspected bad add-ons using their support website or email. 
#Start OS in safe mode. Instructions: [https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode win10], [https://support.microsoft.com/en-us/help/17076/windows-8-startup-settings-safe-mode win8], [https://support.microsoft.com/en-us/help/17419/windows-7-advanced-startup-options-safe-mode#start-computer-safe-mode=windows-7 win7], [https://support.apple.com/kb/PH25617?locale=en_US MacOS]. If performance is improved in safe mode, then 
#* check for newer version of AV/firewall software, and check with vendor's support site for problem reports 
#* test with antivirus disabled or removed - because we constantly see reports of antivirus causing slowness, and disabling isn't always reliable. See [[Thunderbird:Testing:Antivirus Related Performance Issues|AV performance issues]] for examples and settings. 
#* on Windows, especially Windows 10, try disabling MS-Windows Search (see next numbered item below)
#* test with firewall disabled or removed <small>[https://support.mozilla.org/en-US/questions/1133857 Ad-Aware example]</small> 
#* any software loaded at boot time is a possible cause
#*run only one antivirus, one firewall, one malware (never multiples of each - more is not better)
#*on Mac, try with [https://support.apple.com/kb/PH25607 Time Machine disabled]
#*uninstall Thunderbird, then '''DELETE''' the Thunderbird '''PROGRAM''' directory (not the data directory), then [https://www.mozilla.org/thunderbird/ download], reinstall, and retest Thunderbird. <small>If using beta get it from [https://www.thunderbird.net/download/beta/ channels].</small>  
#Do you have Calendars? Try disabling two or more at a time. If you have many recurring, never ending calendar appointments try reducing the time period and number of them. <small>Less likely starting with version 128's fix for {{bug|1844408}}. Examples: [https://www.reddit.com/r/Thunderbird/comments/16c89wo], [https://www.reddit.com/r/Thunderbird/comments/18ypd8r/comment/kgcyox8/] </small>
#If you have gmail accounts, is problem gone after [http://kb.mozillazine.org/Using_Gmail_with_Thunderbird_and_Mozilla_Suite#Subscriptions unsubscribing the "All Mail" folder]? 
# On Windows, did you move the Thunderbird profile directory or any Thunderbird account from the default location "[https://www.nextofwindows.com/how-to-access-user-profiles-appdata-folder-the-easiest-way-in-windows-7 %APPDATA%]"?  If yes, then MS-Windows Search will [https://bugzilla.mozilla.org/show_bug.cgi?id=1083233 attempt to index all Thunderbird disk activity]. [http://www.sevenforums.com/general-discussion/215354-how-prevent-showing-search-results-drive-folder.html#post1805728 Disable Windows indexing for your Thunderbird data].
#Folders should be well maintained - if not then the folder index takes more memory and time to load. Help | Troubleshooting lists large folders. Folders may also be broken. Signs of problems and common maintenance steps:
#* Do you see high memory or delay when opening a specific folder, deleting or archiving, moving message to a specific folder? 
#* Do any folders lose their sort order or column settings?
#* Do you empty Trash and Spam (junk) folders on a regular basis? '''These should not be larger than a few thousand messages, and you should not use these folders for long term storage. Does performance improve if you empty them?''' <small>An alternative to manual emptying is setting automatic retention value in Folder Properties.  Also see [https://support.mozilla.org/en-US/questions/1226726, [https://support.mozilla.org/en-US/kb/menu-reference#w_empty-trash File menu], {{bug|1192827}}</small>
#* Do any Inbox or filtered folders have several thousand messages?  If so, especially for Inbox, consider moving some messages to another folder. Perhaps use [https://support.mozilla.org/en-US/kb/archived-messages Archive].
#* Are [https://support.mozilla.org/en-US/kb/compacting-folders compacts] routinely performed?  Compact must be automatic or done regularly (at least weekly) using [https://support.mozilla.org/en-US/kb/menu-reference#w_compact-folders manual File > Compact Folders]?
#If [[#Memory Overview|Thunderbird memory usage is more than 1-2GB]] then perhaps  folders are corrupted or not being closed. Please : 
#*Get a diagnostic log of Thunderbird activity with '''MSGDB:5,timestamp''' using [[MailNews:Logging|logging instructions]]. <!-- You must install and use [ftp://ftp.mozilla.org/pub/thunderbird/nightly/latest-comm-1.9.2/ a 3.1beta build appropriate to your OS]  [http://s3.mozillamessaging.com/build/try-server/list.html tryserver build] appropriate to your platform that includes ''010-01-14_08:10-bienvenu@nventure.com-1263484981/bienvenu@nventure.com-1263484981-mail-try'' in the name --> 
#*[https://bugzilla.mozilla.org/enter_bug.cgi?product=Thunderbird&format=guided File a bug], then edit the new bug and attach the zipped log file using "Add an attachment". 
#Does setting Thunderbird to offline mode help?  <small>File | Offline | Work Offline - Work Offline should be "checked" - this stops checks for new mail, news and RSS feeds.</small>
#* If Offline did not help, do File | Offline | Work Offline - Work Offline should now be "unchecked".
#* If Offline did help, then go back Online (disable Offline) and ...:
#**Does disabling interval checks for new mail help? (Account Settings | Server Settings | uncheck "Check for new messages every N minutes").  If it helps, then ... is a low value (1-3 minutes) specified for checking for new mail?  <small>Does increasing it to 5-10 minutes help?</small> 
#**Is a low value (1-3 minutes) specified for draft autosave at Options | Composition | General | Auto Save every N minutes. <small>Does increasing it to 5-10 minutes help?</small>
#**What type of mail account is this (imap or pop), and how many other accounts are the same type?
#**Are you absolutely certain that antivirus software is not to blame?
#**Are any non-Inbox IMAP folders configured to check for new messages via "always check this folder" in properties?  Or is hidden preference mail.check_all_imap_folders_for_new set to true? These increase load on both Thunderbird and the mail server. <small>{{Bug|729504}}</small>
#Does problem resolve by disabling Global Search indexing? <small>Tools|Options|Advanced|General| uncheck Enable Global Search and Indexer (linux: Edit|Preferences|Advanced|...  Mac: cmd , advanced tab) '''and restart Thunderbird.'''  (note, disabling indexing also disables searching) </small> 
#* If problem did not go away, or to recheck indexing behavior, enable the checkbox again and restart Thunderbird.
#* If the problem did go away - did Thunderbird have extremely high disk IO, seem to be stuck on indexing per Tools|Activity Manager, or is global-messages-db.sqlite (file used for global search) in your [http://kb.mozillazine.org/Profile_folder_-_Thunderbird profile folder] too big? <small>Rule of thumb - the file should not be more than 10-20% of the combined size of all messages in directories Mail and ImapMail.</small>
#**Rename global-messages-db.sqlite (to keep it for later diagnosis), enable the Global Search checkbox, and restart Thunderbird. global-messages-db.sqlite will rebuild and your system load may be high until all your messages are reindexed, but your messages should not redownload from the server.
#**Please [https://bugzilla.mozilla.org/enter_bug.cgi?product=Thunderbird&format=guided file a bug] about your problem. 
#Are any of these indexing methods enabled in Thunderbird:
#* MS-Windows Integrated Search enable/disable at Tools|Settings|General|System Integration|Allow Windows Search [https://bugzilla.mozilla.org/show_bug.cgi?id=1294985#c9], [http://forums.mozillazine.org/viewtopic.php?p=14787494&sid=65155af350753b1b533816f9aa186ec2#p14787494], [http://forums.mozillazine.org/viewtopic.php?f=39&t=2998289&sid=b7f14103cb12448f427da681a0ba45c8&p=14571029#p14571029], [http://groups.google.com/group/mozilla.support.thunderbird/browse_thread/thread/93ab6d849bd87918/db493affc19d6520?lnk=gst&q=%22TB+3.1+Freezes%22+%22also+found%22#db493affc19d6520], [http://forums.mozillazine.org/viewtopic.php?p=14283935&#p14283935], [http://forums.mozillazine.org/viewtopic.php?f=39&t=2957945&p=14430851#p14430851], [https://support.mozilla.org/en-US/questions/1102258], [https://support.mozilla.org/en-US/questions/1154444]
#* MS-Windows Search service [http://forums.mozillazine.org/viewtopic.php?p=13750937#p13750937 try disabling], especially with [https://bugzilla.mozilla.org/show_bug.cgi?id=1262517 Windows 10], {{bug|1436278}}, or if you moved Thunderbird profile or account from the default location [https://support.mozilla.org/en-US/questions/1117146?page=2#answer-885401], [https://bugzilla.mozilla.org/show_bug.cgi?id=1083233], [https://bugzilla.mozilla.org/show_bug.cgi?id=1283908]. If that helps, you can [http://www.sevenforums.com/general-discussion/215354-how-prevent-showing-search-results-drive-folder.html#post1805728 disable Windows indexing for your Thunderbird data].
#* Mac Spotlight at Thunderbird|Settings|System Integration
#Do you have thousands of contacts in your address book? <small>(possible related issues:  google contacts add-on], [http://hogiblog.blogspot.com/2012/01/reducing-memory-usage-of-google.html?showComment=1333621724776#comment-c8055257360225747824]</small>
<!-- fixed in 76 #Are you using chat? {{bug|1575214}} -->
#Do you see "Unresponsive Script" or "Not Responding"?  If you do, is Thunderbird whitelisted in your [[Thunderbird:Testing:Antivirus Related Performance Issues|antivirus software]]?  If whitelisting didn't help, set javascript.options.mem.log to true and provide a couple log entries of the form <small> CC(T+1186.6) collected: 131 (131 waiting for GC), suspected: 98, duration: 274 ms.</small>
#Has a proxy ever been defined, and is it working correctly or was the proxy removed?  (A proxy can cause "Unresponsive script")
#Does turning off the status bar in View > Toolbars help improve performance?
#If you see high CPU usage in Windows taskmgr, sort the CPU column in the details tab to see if [http://forums.mozillazine.org/viewtopic.php?p=12641015#p12641015 mozilla updater.exe], Window's update, or some other process is hogging CPU.
#Is your '''[https://support.mozilla.org/en-US/kb/profiles-tb Thunderbird profile]''' or any part of Thunderbird <u>not</u> on a local hard drive? If not local, does it preform better when it is moved to the local disk?
#* Cloud storage is not supported.
#* USB drives are slower compared to a local disk. Some types or manufacturers are terrible. [http://portableapps.com/shop/hardware Make sure you've got a good one.]
#* network drive can be slow due to network transmission or slow media (SMB, NFS, AFS, samba)
#* SSD?  (sounds silly, but some SSD have been reported to be slow)
#If you suspect slow disk or high disk activity
#* check the previous item (NFS, etc)
#* in Windows you want at least 20% free disk space, and for spinning disks do periodic defrags
#* check whether any OS or application update process is in progress, for example [https://support.mozilla.org/en-US/questions/1226979 Windows update]
#How many virtual folders have you created?
#If you have newsgroup accounts, then in Account Settings|Server Settings try disabling "Check for new messages at startup". <small>If problem is gone you may be seeing [https://groups.google.com/d/msg/mozilla.support.thunderbird/_6yvdz0de9g/9KJVVBqIAwAJ many newsgroups with many unread messages], {{bug|185634}}, {{Bug|541001}}, or [http://forums.mozillazine.org/viewtopic.php?p=9900989&sid=e32e1e42a3ddcac8c8605a1cbea6b2e8#p9900989].</small> 
#If you have RSS news reader account:
#* Is "Automatically create tags from feed category names" enabled? [https://bugzilla.mozilla.org/show_bug.cgi?id=1342054] 
#* In Account Settings|Server Settings disable "Check for new messages at startup". <small>If problem is gone you may be seeing {{Bug|551144}} (fixed in version 13).</small> 
# Any Outlook or Hotmail accounts? {{Bug|1355885}}
#Is filter logging enabled at Tools > Filters?  (large logs cause high overhead)
#Do you use server side message filters to place messages in folders? <small>{{Bug|589310}}</small>
#Check activity in Tools > Activity Manager to see if ISP (mail provider) is being lame. Examples: Yahoo and Gmail (and others) may cause message folders to be redownloaded.  <small>[https://support.mozilla.org/en-US/questions/1202731 slow downloading email (Centurylink)]</small>
#Common resource requirements, hardware checks:
#* Do you have the [https://www.mozilla.org/en-US/thunderbird/52.0/system-requirements/ minimum hardware requirements], including [[#Memory_Overview|memory]]? <small>NOTE: minimum recommended size may not be sufficient for <u>your</u> Thunderbird and total system's workload.</small>
#* Consider hardware or virtualization problems [http://forums.mozillazine.org/viewtopic.php?p=14414969#p14414969], [https://support.mozilla.org/en-US/questions/1090651]
#* Check BIOS settings: [[http://forums.mozillazine.org/viewtopic.php?f=39&t=3033410 hanging when sending messages if VT-x is enabled in BIOS]]
#* If Thunderbird is running in a VM (virtual machine), does it run much better when running not virtualized?
#Are you using Linux?
#*A package might be causing the problem [https://www.reddit.com/r/Thunderbird/comments/183tc5h/suddenly_slow_thunderbird_on_linux_gentoo_how_to/]
#*Are you running an old version of linux, consider updating. [http://forums.mozillazine.org/viewtopic.php?p=13605851#p13605851 hangs on Ubuntu 10.04, 14.04 works]
#If you have a reportable problem or question, please use the next section below.

<!-- not a factor since version 91 # Is panacea.dat cache file in [https://support.mozilla.org/en-US/kb/profiles-tb your profile] too big? <small>(>10MB is probably too big. Calculate with thunderbird stopped: is panacea.dat larger than #folders*0.3k? See [https://bugzilla.mozilla.org/show_bug.cgi?id=65086#c34 bug 65086], {{bug|1084276}})</small> -->

== Report a problem ==

[[#Before starting|Provide all the information you have collected]] plus the URL to a [https://support.mozilla.org/kb/profiling-thunderbird-performance performance profile which you create] in one of the following:
*An existing bug report that matches your problem.  Check the [[#References|curated bug list in this document]] or [https://mzl.la/3Xg2Bsg list of open performance bug reports]. 
*Create a [https://support.mozilla.org/en-US/questions/new/thunderbird/form support request] or [https://bugzilla.mozilla.org/enter_bug.cgi?product=Thunderbird&format=guided new bug report].

= References  =
'''"Not Responding"''' - '''Examples''': [https://support.mozilla.org/en-US/questions/1205100 BTTray.exe], [http://forums.mozillazine.org/viewtopic.php?p=13846427#p13846427 (Plusnet Protect/McAfee)], [http://forums.mozillazine.org/viewtopic.php?p=13127165#p13127165 McAfee], [http://forums.mozillazine.org/viewtopic.php?p=13750937#p13750937 WSS, Windows Search Indexing] and [https://bugzilla.mozilla.org/show_bug.cgi?id=1283908], [http://forums.mozillazine.org/viewtopic.php?p=13483493#p13483493 McAfee], [http://forums.mozillazine.org/viewtopic.php?p=13482389#p13482389 McAfee], [http://forums.mozillazine.org/viewtopic.php?p=13132457#p13132457 McAfee (2013)] '''Solutions''': [http://forums.mozillazine.org/viewtopic.php?p=13597865#p13597865 use XP3 compatibility mode in Windows 8 (Endicott)], [http://forums.mozillazine.org/viewtopic.php?p=13615031&sid=fb04bf69001ad087d98eb654464ebe9b#p13615031 use XP3 compatibility mode (missychrissy)], [http://forums.mozillazine.org/viewtopic.php?p=13119947 use XP3 compatibility mode (WaddyT/2013)], [http://forums.mozillazine.org/viewtopic.php?f=39&t=2843195&p=13719551#p13719551 use XP3 compatibility mode in Windows 8 (kgcode)]

'''"Unresponsive Script"''' - '''Examples''':  '''Solutions''': 

'''Unresolved bugs and references:'''
<!-- http://bit.ly/cQowd5 major + critical perf bugs -->
* '''[[Thunderbird:Testing:Antivirus_Related_Performance_Issues#McAfee|McAfee antivirus]] is causing major performance and problems with TB24 (and was with TB17 and TB16). Symptom: slow delete and read, "Unresponsive Script", "(Not Responding)".  [[Thunderbird:Testing:Antivirus_Related_Performance_Issues#McAfee|Solution]]'''
*{{Bug|1342054}} - Large number of tags causes very bad tags preference UI performance, from autotaging RSS feeds with "Automatically create tags from feed category names"
*{{Bug|1438317}} - "Indexing messages. Determining which messages to index" stuck on local folder never ends. Modest CPU - 7-10%. Error console "Observed header that claims to be gloda indexed but that gloda has never heard of during compaction"
*{{Bug|1406653}} - Gloda warning repeated every half-second causing high cpu and slow response. "Observed header that claims to be gloda indexed but that gloda has never heard of during compaction" in error console and "Determining which messages to index"" 
*{{Bug|1240722}} - tidybird add-on causes files/folders to be opened and stay open twice - Thunderbird leaks file descriptors (mostly .msf files) like a sieve causing high memory. (no virtual folders)
*{{Bug|929281}} - Long startup and "Unresponsive Script" with many pop accounts with version 24 (regression in TB18)
*{{Bug|764306}} - When trying to scroll large folders or switch some folders the application beachballs with high CPU (xref: {{Bug|872869}})
* High mem usage, increasing with every delete.  No bug report. Solved by right+click, compact. 
* {{bug|632791}} Gloda (Global Search) indexes one message per minute with high CPU. Excessively sized global-messages-db.sqlite caused by buggered, excessively sized offline store. [because offline folder storage has many duplicate messages. but it should not]
*{{bug|563677}} HTML Mail View slow (45++ sec) for pop and local folders - speed up FolderUriForPath (from {{Bug|545126}})
*{{Bug|487832}} - Thunderbird startup performance issues [meta]
*{{Bug 357008}} - (If you have a profile created between version 1.5 and 2.0) Remove obsolete directory address books entries from prefs

* ref: [http://kb.mozillazine.org/Performance_%28Thunderbird%29 Thunderbird Performance knowledge base article] 
* ref: [http://kb.mozillazine.org/Standard_diagnostic_-_Thunderbird Standard diagnostic for Thunderbird knowledge base article ] 
* ref: {{Bug|480841}} Implement memory reporter for Gloda 
* ref: {{Bug|480843}} Implement memory reporter for mailnews

*Lightning related:
**{{Bug|441710}} - Thunderbird freezes/slow for 3-60 seconds caused by calendar/lightning [meta] 
**{{bug|753343}} - Soft-hang and massive memory leaks with Lightning and ics enabled
**{{bug|501689}} - Investigate making storage asynchronous // {{bug|462277}} - (calcache) [meta][GSoC 2014] Turn on offline cache by default for new calendars
**{{bug|498968}} - Create a new, faster storage "storage2" provider
*[http://tinyurl.com/l7t52zo larger, less selective list of bugs] inclusive of those cited above

Bugs fixed but not released.  Typically fixed in unreleased versions (eg. trunk regressions):
* {{Bug|1502923}} - Thunderbird processing / "Not Responding"  5 to 30 minutes at startup. Also "Unresponsive Script" - Performance issues in unifinder.js

'''Fixed bugs/issues:'''

<!-- list updated 2018-04-07 -->
Performance bugs fixed in 60.0:
*{{Bug|1293245}} message with malformed email address makes Thunderbird hang 100% CPU load (also some crashes)
<!-- cf. bug 1411720 -->
<!-- Regressions fixed in unreleased versions (53-60) -->
*{{Bug|1428082}} - Thunderbird Daily becomes unresponsive when Add-ons Manager opened from hamburger after bug 1427407 landed (TB59,fixed TB60)
*{{Bug|1415723}} - Severe regression in at least Tb55 when repairing/rebuilding/compacting folder database (msf) file. (TB55, fixed TB59)
*{{Bug|1404003}} Daily from 2017-09-28 re-downloads and indexes messages at every start - high CPU (TB58, fixed TB58)
*{{Bug|1116196}} - Every startup, Warning: Unresponsive Script after approx 15 seconds, with system integration prompt (regression in TB18, stopped appearing in TB54beta)

Performance bugs fixed in 52.0.x:
*{{Bug|1290733}} - UpdateSendLock() in compose window is very slow (TB23, fixed TB51)
*{{Bug|562965}} - folderPane.js ftv_getRowProperties/ftv_getCellProperties disproportionately slow
*{{Bug|1290729}} - Adding new recipients in compose is very slow
*{{Bug|1242050}} - Default output *stream* buffer size of 16KB instead of 4KB
*{{Bug|558528}} - Larger *disk* buffer size, 16KB instead of 4KB, in file I/O by Mail&News to improve performance on slower drives (for example network drives/shares). 
<!-- this didn't actually land a perf improvement Bug 1116055 - Performance issue: Failure to use buffered write - Part 1: Collect file seek position information. -->

Performance bugs fixed in 45.0.x:
*{{Bug|1223371}} - remove windows search, aka integrated search, from Thunderbird System integration dialog startup prompt (not an actual perf improvement, just avoids tempting uneducated users from picking it)

<!-- list updated 2015-06-08 -->
Resolved at unknown date
*{{Bug|1185245}} - Hardware acceleration (HWA) may cause message compose window to lag severely (WFM)

Performance bugs fixed in 38.0:
*{{Bug|872869}} - nsMsgDatabase::ListAllKeys() very slow with high CPU downloading messages into large folder (xref: {{bug|764306}}) (regression in TB16)
*{{Bug|846123}} - Thunderbird 100% CPU for minutes when copying a large number of messages (IMAP Online Copy, Copy between Offline-Use=Off folders) (landed in TB37)
*{{Bug|939462}} - Feature to count and show number of unread e-mails in subfolders should be optional. (because enumeration is slow) (regression in TB15)  Fixed by {{Bug|1135310}} Algorithm from bug 723248 for closing idle folder databases is broken because too many/all databases can be closed and {{Bug|464973}} "Expanded Columns" in the folder pane are no longer available to select columns for display for message total count and folder size
*{{Bug|870556}} - O(n^2) performance freezes UI for several minutes fetching new mail from IMAP server for very large folder
*{{Bug|778907}} - Highlighting/selecting 18000+ of emails inside a folder keeps giving the javascript is unresponsive script ("bulkoperations", i.e. not a general performance issue) (landed in TB36)
*{{Bug|1050840}} - "Maximum number of imap server connections to cache" advanced account setting defaults to 1 for new accounts (regression in TB24)

Performance bugs fixed in 31.0:
*{{Bug|975795}} - extremely slow for large selections, because folderDisplay.canArchiveSelectedMessages is too slow (landed in TB30) (helped by {{Bug|943116}} and {{Bug|942638}})
*{{Bug|1019969}} - (resolved WFM, cause and fix unknown) Thunderbird 18-30b1 gets "Unresponsive script" 45 seconds after launch/startup. OK in 31.0
*{{Bug|926181}} - Thunderbird 24 OSX freezes on startup with profile on network drive (AFP) - fixed via {{Bug|918612}} - Mac: Firefox 24 doesn't start, or very slow startup

Performance bugs fixed in 24.0:
*{{Bug|812923}} - Dragging a huge number of messages onto a folder freezes TB even BEFORE dropping (TB24)
*{{Bug|750781}} - Thunderbird 12 veryyyyy slow when opening Message. Sometimes shows "Not Responding" (TB21)
*{{Bug|810637}} - HUGE memory consumption when downloading headers for large IMAP folder with mailnews.customDBHeaders (TB19)

Performance bugs fixed in 17.0:
*{{Bug|806760}} -  TB16 Redownloads messages / Constantly bringing folders "up to date" / horrible IMAP performance (TB16 regression)
*{{Bug|769346}} - Poor performance of Move, Copy and Delete to Local Folders due to "one write request per a line of message data"

Performance bugs fixed in 16.0.2:
*{{Bug|803843}} - IMAP mailfiles keep growing to gigabyte size

Performance bugs fixed in 16:
*{{Bug|793455}} - DB cache is closing databases too frequently (regression in 15.0)
*{{Bug|770416}} - (insignificant?) memory leak on some IMAP operations

Performance bugs fixed in 15.0.1:
*{{Bug|782899}} - Daily hangs and leaks memory like crazy when trying to delete messages in the results of a filter search (regression in 15.0)

Performance bugs fixed in 15.0:
*{{Bug|784286}} - Abnormal memory requirements viewing plain-text mail leading to crash 
*{{Bug|723248}} - add support for closing inactive databases (folders)
*{{Bug|762169}} - Always asking to compact folders starting version 12

Performance bugs fixed in 14.0:
*{{Bug|538378}} - Mass delete of messages resulted in massive memory usage // {{Bug|296453}} - Racing CPU, slow performance moving/deleting/dragging large number of messages

Performance bugs fixed in 13.0:
*{{Bug|551144}} - checking rss feeds has problem freezing Thunderbird UI and high hard drive usage (not a v3 or v3.1 regression)

Performance bugs fixed in 10.0:
* improved gloda (globa indexing) efficiency via: {{Bug|677805}}, {{Bug|554015}}, {{Bug|554033}}, {{Bug|678405}}

Performance bugs fixed in 9.0:
* {{bug|689742}} - Disable hardware acceleration (direct2d) in Thunderbird 

Performance bugs fixed in 5.0
*{{bug|574952}} - Thunderbird 3.1 account list / folder pane slow to scroll on Mac (Mac-only)
*{{Bug|617839}} - Switching to threads with a large number of emails is extremely slow

Performance bugs fixed in 3.1.5:
* {{Bug|542234}} memory increases about 12MB on each check for new mail for pop accounts, 3.0 & 3.1
* {{Bug|599119}} slow message display/slow navigation - plugin directory scans cause excessive overhead

Performance bugs fixed in 3.0.9:
* {{Bug|542234}} memory increases about 12MB on each check for new mail for pop accounts, 3.0 & 3.1

Performance bugs fixed in 3.0.5:
*{{Bug|530098}} gloda message deletion processing is expensive

Performance bugs fixed in 3.1:
<!-- http://hg.mozilla.org/users/bugzilla_standard8.plus.com/drivertools/raw-file/default/bugtracking/index.html?branch=3.1 -->
*{{Bug|533776}} gloda indexes while offline, if we startup without a network connection
*{{Bug|539389}} Very slow file manipulation deleting or moving messages (profile stored on synchronized network folder). Tb3 requests write for each line of mail data. Should use buffering.
*{{Bug|545126}}HTML Mail View very slow (45++ sec) for pop and local folders (*not* fixed in v3.0.x) / {{Bug|536873}} slow load HTML messages with View Message Body as Original HTML - sits at "Loading Message ..." or presents blank screen
*{{Bug|530098}} gloda message deletion processing is expensive (*not* fixed in v3.0.x)
*{{Bug|493848}} gloda activity manager should not create events for event-driven indexing, never display in status bar (*not* fixed in v3.0.x)
*{{Bug|543737}} gloda needs to avoid indexing ridiculously large message bodies (especially from offline store corruption) (indexing stops at 20k per message part)(*not* fixed in v3.0.x)
*{{Bug|560695}} clicking (more) widget in headers with lots of recipients too slow (*not* fixed in v3.0.x)

Performance bugs fixed in 3.0.4: 
<!-- http://bit.ly/9TRymz -->
*{{Bug|533776}} gloda indexes while offline, if we startup without a network connection
*{{Bug|539389}} Very slow file manipulation deleting or moving messages (profile stored on synchronized network folder). Tb3 requests write for each line of mail data. Should use buffering.

Memory related bugs fixed in 3.0.2/3.0.3:
*{{Bug|540214}} imap STATUS not closing db - mail.check_all_imap_folders_for_new and "check this folder for new messages" causes high memory and error message Unable to open the summary file for xxxxx. Perhaps there was an error on disk, or the full path is too long.

Performance related bugs fixed in 3.0.1: 
*{{Bug|534835}} offline folder size constantly increases using Exchange IMAP (Exchange returns wrong rfc822 size) - messages redownload 
*{{Bug|537820}} quick search in smart folders/saved searches should prefer offline when it has a choice 
*{{Bug|533865}} Doing a quick search in a cross-folder saved search clears cached results

Memory related bugs fixed in 3.0
* {{Bug|525646}} Mass delete of messages resulted in massive memory usage (not sustained usage, and was v3-only behavior I think, i.e. not from v2)

Fixed in version 2 and / or prior to releasing version 3.0: 

*RSS 
*google desktop search 
*{{Bug|465353}} general sluggish, lack of responsiveness during indexing of gloda (indexing speed kills CPU and performance)
*{{Bug|518918}} Thunderbird 3pre high memory and consuming 100% CPU making mail nearly unusable, need to handle UID's &gt; 0x7FFFFFFF (fixed in 3.0.0) 
*{{Bug|465122}} Gloda: Does not close msf files on initial indexing 
*{{bug|387403}}  Thunderbird eat memory until crash when opening e-mail with broken vcard (fixed in version 2.0.0.13) 
*{{Bug|216535}} large mailboxes seem to cause pathological memory usage, was duped to ...
*{{Bug|266679}} Thunderbird consumes excessive file-handles and memory (fixed 1.5.&lt;something&gt;, and before release of 2.0)

= Memory Overview  =

{| cellspacing="1" cellpadding="2" border="1" summary="List of other pages related to this one"
|+ '''Related Articles''' 
|-
| 
*[[Thunderbird:Testing:Antivirus Related Performance Issues|Performance Issues with Antivirus Software]]<br>
*[http://kb.mozillazine.org/Keep_it_working_%28Thunderbird%29#Routine_usage Routine maintenance]
|}

<small>If you don't need background information about memory, please skip to diagnosis steps.</small>

"How much memory is needed run Thunderbird?" is a frequently asked question. [https://www.mozilla.org/en-US/thunderbird/31.0/system-requirements/ System Requirements] defines minimum Thunderbird machine requirements for a "mythical" user. But, these are just minimums, and do not describe how much memory you might need in your "real" environment.  A better answer of what is enough memory might be ...: 
:a) It depends on your Thunderbird configuration (number of large folders, number of accounts, etc)
:b) It depends on what you are measuring or doing in Thunderbird at a specific time, because some operations require more memory than others. Like when you are doing mundane things like reading new messages versus when you are searching for messages. 
:c) Current versions require roughly at least 80 MB to 100 MB more memory than version 2. So (for example) if your version 2 used 50MB, then v3 might use 130 MB to 150 MB.  

'''Which memory to measure ...''' 
* MS Windows - '''Working Set/Mem Usage''' of thunderbird.exe (start taskmgr from ctrl+alt+delete, click Processes tab), '''and''' both Total and Available physical memory from the Performance tab.
* Mac - '''Real Private Memory''' of thunderbird (process manager, right click on column bar, select Real) 
* linux - '''RSS/RES''' (Reserved Segment Size) for thunderbird

Rules of thumb (these are not "laws") for an average user with NO addons ... after a day of using Thunderbird, if memory usage is :
* less than 250MB, then you are OK. 
* not much above your version 2 memory usage plus 100MB, then you are probably OK.
* is over 300MB, then you may have a problem that needs analysis. 
* increasing significantly over a period of day or more, and never drops back below 300MB, i.e. it increases cumulatively over time then you may have a problem. <small>For example, if you click on a folder and memory increases by 10MB and stays at that level or higher forever, and next time you click the same folder and memory increases another 10MB and stays at that level or higher forever ..., then you have a problem.</small>

<!-- <u>'''Non-sustained'''</u> in this context not about peak usage. It means very high memory usage that is temporary, not constant.  -->
Note: memory usage is affected by the number and types of extensions (add-ons) installed, number of folders and accounts, number of messages in folders, and [[Thunderbird:Testing:Memory_Usage_Problems#References|bugs]]. 
<!--#[[#Other_Software|Other Software]] (listed below)
# folder files not closed by the operation system or other software (including  Thunderbird) after it is done using a folder (internally called a db, or database) 
#Large folders with high delete activity that you rarely compact. Or where compact fails because of a bug (eg. {{bug|nnn}}), or the folder has grown too large to be compacted. 
#Moving large numbers of messages via drag and drop 
#Buggy servers or corrupted local files, including calendar data and servers

The items below may also increase memory usage, but not so high as to cause problems under normal circumstances: 

*virtual folders 
*extensions/add-ons
*extremely large folders 
*gloda global database - new in v3(_need references_) 
*plugins (_need references_) 
*[[#Memory_Leaks|'Memory leaks']]
-->
= Other Software  =

Add-ons / Extensions reported to have caused high memory, performance, or other problems:

*[https://www.reddit.com/r/Thunderbird/comments/1er8r8k/comment/lk5tdms/ darkreader]
*[https://support.mozilla.org/en-US/questions/1062821 Adblock Plus]
*[http://forums.mozillazine.org/viewtopic.php?p=13773869#p13773869 Cloudmark DesktopOne], [https://support.mozilla.org/en-US/questions/1141111 Cloudmark DesktopOne again]
*[http://forums.mozillazine.org/viewtopic.php?p=11883641#p11883641 Google Contacts]
*[http://forums.mozillazine.org/viewtopic.php?p=12072563#p12072563 Everygain Translator]
*[http://forums.mozillazine.org/viewtopic.php?p=10104785#p10104785 mailtweak] (slowness)
*enigmail: {{Bug|519226}} extremely high memory requirements on Linux with Enigmail, [https://bugzilla.mozilla.org/show_bug.cgi?id=803429#c36 high cpu with enigmail]
* <strike> junquilla (slowness) {{Bug|505577}} Scrolling in folder pane is choppy, slow, with high memory (fixed in current release)</strike> 
*Quicktext (slowness) 
*ThunderBrowse (slowness) 
*google desktop search

Programs (firewall, antivirus, etc) reported to have caused high memory, performance or other problems: 

* ogplanet Game Launcher/npOGPPlugin.dll {{Bug|543082}} slow opening an email on windows
*Secunia PSI 
*THE SHIELD {{bug|542156}} 
*Eset NOD32 {{Bug|541197}} Repeated attempts to create huge temporary file during message synchronization due to Eset NOD32 causes slow gloda indexing 
*F-Prot Antivirus may cause very slow access to mailbox files. See: [[Thunderbird:Testing:Antivirus Related Performance Issues|Antivirus Related Performance Issues]]

Miscellaneous
* [https://thunderbirdtweaks.blogspot.com.au/2016/08/windows-10-and-thunderbird-firefox.html PCI express power setting]

= Terminology =

*memory usage - varies per OS: in Windows XP taskmgr the column is 'Mem Usage', in Vista it is 'Working Set' 
*[https://developer.mozilla.org/En/Glossary Glossary]

= References =
* [http://kb.mozillazine.org/Performance_-_Thunderbird Thunderbird Performance]
* [http://kb.mozillazine.org/Keep_it_working_%28Thunderbird%29#Routine_usage Routine maintenance]