Some users have reported solving this problem by resetting the NVRAM (PRAM.) One user reports long delays in waking from sleep after enabling FileVault. I can't reproduce that experience, but if applicable, you could try disabling FileVault.

If you've installed something called "iCleanMemory," or any other third-party software that is supposed to "clean" or "free up" memory, remove it according to the developer's instructions after backing up all data. Restart the computer and test. If there's no change, continue.

This procedure is a diagnostic test. It’s unlikely to solve your problem. Don’t be disappointed when you find that nothing has changed after you complete it.

The purpose of the test is to determine whether the problem is caused by third-party software that loads automatically at startup or login, by a peripheral device, by a font conflict, or by corruption of the file system or of certain system caches.

Disconnect all wired peripherals except those needed for the test, and remove all aftermarket expansion cards, if applicable. Start up in safe mode and log in to the account with the problem. You must hold down the shift key twice: once when you turn on the computer, and again when you log in.

Note: If FileVault is enabled, or if a firmware password is set, or if the startup volume is a Fusion Drive or a software RAID, you can’t do this. Ask for further instructions.

Safe mode is much slower to start up and run than normal, with limited graphics performance, and some things won’t work at all, including sound output and Wi-Fi on certain models. The next normal startup may also be somewhat slow.

The login screen appears even if you usually login automatically. You must know your login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.

Test while in safe mode. Same problem?

After testing, restart as usual (not in safe mode) and verify that you still have the problem. Post the results of the test.

1. This procedure is a diagnostic test. It changes nothing, for better or worse, and therefore will not, in itself, solve the problem. But with the aid of the test results, the solution may take a few minutes, instead of hours or days.

Don't be put off merely by the seeming complexity of these instructions. The process is much less complicated than the description. You do harder tasks with the computer all the time.

2. If you don't already have a current backup, back up all data before doing anything else. The backup is necessary on general principle, not because of anything in the test procedure. Backup is always a must, and when you're having any kind of trouble with the computer, you may be at higher than usual risk of losing data, whether you follow these instructions or not.

There are ways to back up a computer that isn't fully functional. Ask if you need guidance.

3. Below are instructions to run a UNIX shell script, a type of program. All it does is to collect information about the state of the computer. That information goes nowhere unless you choose to share it. However, you should be cautious about running any kind of program (not just a shell script) at the behest of a stranger. If you have doubts, search this site for other discussions in which this procedure has been followed without any report of ill effects. If you can't satisfy yourself that the instructions are safe, don't follow them. Ask for other options.

Here's a summary of what you need to do, if you choose to proceed:

• Copy a line of text in this window to the Clipboard.
• Paste into the window of another application.
• Wait for the test to run. It usually takes a few minutes.
• Paste the results, which will have been copied automatically, back into a reply on this page.

The sequence is: copy, paste, wait, paste again. You don't need to copy a second time. Details follow.

4. You may have started the computer in "safe" mode. Preferably, these steps should be taken in “normal” mode, under the conditions in which the problem is reproduced. If the system is now in safe mode and works well enough in normal mode to run the test, restart as usual. If you can only test in safe mode, do that.

5. If you have more than one user, and the one affected by the problem is not an administrator, then please run the test twice: once while logged in as the affected user, and once as an administrator. The results may be different. The user that is created automatically on a new computer when you start it for the first time is an administrator. If you can't log in as an administrator, test as the affected user. Most personal Macs have only one user, and in that case this section doesn’t apply. Don't log in as root.

6. The script is a single long line, all of which must be selected. You can accomplish this easily by triple-clicking anywhere in the line. The whole line will highlight, though you may not see all of it in the browser window, and you can then copy it. If you try to select the line by dragging across the part you can see, you won't get all of it.

Triple-click anywhere in the line of text below on this page to select it:

PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/libexec;clear;cd;p=(Software Hardware Memory Diagnostics Power FireWire Thunderbolt USB Fonts 51 4 1000 25 5120 KiB/s 1024 85 \\b%% 20480 1 MB/s 25000 ports 'com.autodesk.AutoCad com.evenflow.dropbox com.google.GoogleDrive' DYLD_INSERT_LIBRARIES\ DYLD_LIBRARY_PATH -86 ` route -n get default|awk '/e:/{print $2}' ` 25 N\\/A down up 102400 25600 recvfrom sendto CFBundleIdentifier 25 25 25 1000 MB );N5=${#p[@]};p[N5]=` networksetup -listnetworkserviceorder|awk ' NR>1 { sub(/^\([0-9]+\) /,"");n=$0;getline;} $NF=="'${p[26]}')" { sub(/.$/,"",$NF);print n;exit;} ' `;f=('\n%s: %s\n' '\n%s\n\n%s\n' '\nRAM details\n%s\n' %s\ %s '%s\n-\t%s\n' );S0() { echo ' { q=$NF+0;$NF="";u=$(NF-1);$(NF-1)="";gsub(/^ +| +$/,"");if(q>='${p[$1]}') printf("%s (UID %s) is using %s '${p[$2]}'",$0,u,q);} ';};s=(' /^ *$|CSConfigDot/d;s/^ */  /;s/[-0-9A-Fa-f]{22,}/UUID/g;s/(ochat)\.[^.]+(\..+)/\1\2/;/Shared/!s/\/Users\/[^/]+/~/g ' ' s/^ +//;5p;6p;8p;12p;' ' {sub(/^ +/,"")};NR==6;NR==13&&$2<'${p[10]} ' 1s/://;3,6d;/[my].+:/d;s/^ {4}//;H;${ g;s/\n$//;/s: [^EO]|x([^08]|02[^F]|8[^0])/p;} ' ' 5h;6{ H;g;/P/!p;} ' ' ($1~/^Cy/&&$3>'${p[11]}')||($1~/^Cond/&&$2!~/^N/) ' ' /:$/{ N;/:.+:/d;s/ *://;b0'$'\n'' };/^ *(V.+ [0N]|Man).+ /{ s/ 0x.... //;s/[()]//g;s/(.+: )(.+)/ (\2)/;H;};$b0'$'\n'' d;:0'$'\n'' x;s/\n\n//;/Apple[ ,]|Intel|SMSC/d;s/\n.*//;/\)$/p;' ' s/^.*C/C/;H;${ g;/No th|pms/!p;} ' '/= [^GO]/p' '{$1=""};1' ' /Of/!{ s/^.+is |\.//g;p;} ' ' $0&&!/ / { n++;print;} END { if(n<200) print "com.apple.";} ' ' $3~/[0-9]:[0-9]{2}$/ { gsub(/:[0-9:a-f]{14}/,"");} { print|"tail -n'${p[12]}'";} ' ' NR==2&&$4<='${p[13]}' { print $4;} ' ' END { $2/=256;if($2>='${p[15]}') print int($2) } ' ' NR!=13{next};{sub(/[+-]$/,"",$NF)};'"`S0 21 22`" 'NR!=2{next}'"`S0 37 17`" ' NR!=5||$8!~/[RW]/{next};{ $(NF-1)=$1;$NF=int($NF/10000000);for(i=1;i<=3;i++){$i="";$(NF-1-i)="";};};'"`S0 19 20`" 's:^:/:p' '/\.kext\/(Contents\/)?Info\.plist$/p' 's/^.{52}(.+) <.+/\1/p' ' /Launch[AD].+\.plist$/ { n++;print;} END { if(n<200) print "/System/";} ' '/\.xpc\/(Contents\/)?Info\.plist$/p' ' NR>1&&!/0x|\.[0-9]+$|com\.apple\.launchctl\.(Aqua|Background|System)$/ { print $3;} ' ' /\.(framew|lproj)|\):/d;/plist:|:.+(Mach|scrip)/s/:[^:]+//p ' '/root/p' ' !/\/Contents\/.+\/Contents|Applic|Autom|Frameworks/&&/Lib.+\/Info.plist$/ { n++;print;} END { if(n<1000) print "/System/";} ' '/^\/usr\/lib\/.+dylib$/p' ' /Temp|emac/d;/(etc|Preferences)\//s/^\.\/[^/]+//p;' ' /\/(Contents\/.+\/Contents|Frameworks)\/|\.wdgt\/.+\.([bw]|plu)/d;p;' 's/\/(Contents\/)?Info.plist$//;p' ' { gsub("^| ","||kMDItem'${p[35]}'=");sub("^.."," ") };1 ' p '{print $3"\t"$1}' 's/\'$'\t''.+//p' 's/1/On/p' '/Prox.+: [^0]/p' '$2>'${p[9]}'{$2=$2-1;print}' ' BEGIN { i="'${p[26]}'";M1='${p[16]}';M2='${p[18]}';M3='${p[31]}';M4='${p[32]}';} !/^A/ { next;} /%/ { getline;if($5<M1) a="user "$2"%, system "$4"%";} /disk0/&&$4>M2 { b=$3" ops/s, "$4" blocks/s";} $2==i { if(c) { d=$3+$4+$5+$6;next;};if($4>M3||$6>M4) c=int($4/1024)" in, "int($6/1024)" out";} END { if(a) print "CPU: "a;if(b) print "I/O: "b;if(c) print "Net: "c" (KiB/s)";if(d) print "Net errors: "d" packets/s";} ' ' /r\[0\] /&&$NF!~/^1(0|72\.(1[6-9]|2[0-9]|3[0-1])|92\.168)\./ { print $NF;exit;} ' ' !/^T/ { printf "(static)";exit;} ' '/apsd|OpenD/!s/:.+//p' ' (/k:/&&$3!~/(255\.){3}0/ )||(/v6:/&&$2!~/A/ ) ' ' $1~"lR"&&$2<='${p[25]}';$1~"li"&&$3!~"wpa2";' ' BEGIN { FS=":";} { n=split($3,a,".");sub(/_2[01].+/,"",$3);print $2" "$3" "a[n]" "$1;b=b$1;} END { if(b) print("\n\t* Code injection");} ' ' NR!=4{next} {$NF/=10240} '"`S0 27 14`" ' END { if($3~/[0-9]/)print$3;} ' ' BEGIN { L='${p[36]}';} !/^[[:space:]]*(#.*)?$/ { l++;if(l<=L) f=f"\n  "$0;} END { F=FILENAME;if(!F) exit;if(!f) f="\n  [N/A]";"file -b "F|getline T;if(T!~/^(AS.+ (En.+ )?text$|POSIX sh.+ text ex)/) F=F" ("T")";printf("\nContents of %s\n%s\n",F,f);if(l>L) printf("\n  ...and %s more line(s)\n",l-L);} ' ' /^ +[NP].+ =/h;/^( +D.+[{]|[}])/{ g;s/.+= //p;};' ' /^ +B/{ s/.+= |(-[0-9]+)?\.s.+//g;p;} ' ' END{print NR} ' ' /id: N|te: Y/{i++} END{print i} ' ' / / { print "'"${p[28]}"'";exit;};1;' '/ en/!s/\.//p' ' NR!=13{next};{sub(/[+-M]$/,"",$NF)};'"`S0 39 40`" ' $10~/\(L/&&$9!~"localhost" { sub(/.+:/,"",$9);print $1": "$9;} ' '/^ +r/s/.+"(.+)".+/\1/p' 's/(.+\.wdgt)\/(Contents\/)?Info\.plist$/\1/p' 's/^.+\/(.+)\.wdgt$/\1/p' 's/0/Off/p' );c1=(system_profiler pmset\ -g nvram fdesetup find syslog df vm_stat sar ps sudo\ crontab sudo\ iotop top pkgutil PlistBuddy whoami cksum kextstat launchctl sudo\ launchctl crontab 'sudo defaults read' stat lsbom mdfind ' for i in ${p[24]};do ${c1[18]} ${c2[27]} $i;done;' defaults\ read scutil sudo\ dtrace sudo\ profiles sed\ -En awk /S*/*/P*/*/*/C*/*/airport networksetup mdutil sudo\ lsof test );c2=(com.apple.loginwindow\ LoginHook '-c Print /L*/P*/loginw*' '-c Print L*/P*/*loginit*' '-c Print L*/Saf*/*/E*.plist' '~ $TMPDIR.. \( -flags +sappnd,schg,uappnd,uchg -o ! -user $UID -o ! -perm -600 \)' '.??* -path .Trash -prune -o -type d -name *.app -print -prune' '-c Print\ :'${p[35]}' 2>&1' '-c Print\ :Label 2>&1' '{/,}L*/{Con,Pref}* -type f ! -size 0 -name *.plist -exec plutil -s {} \;' "-f'%N: %l' Desktop L*/Keyc*" therm sysload boot-args status " -F '\$Time \$Message' -k Sender kernel -k Message Req 'Beac|caug|dead[^bl]|FAIL|fail|GPU |hfs: Ru|inval|jnl:|last value [1-9]|n Cause: -|NVDA\(|pagin|proc: t|Roamed|rror|ssert|Thrott|tim(ed? ?|ing )o|WARN' -k Message Rne 'Goog|ksadm|SMC:' -o -k Sender fseventsd -k Message Req 'SL' " '-du -n DEV -n EDEV 1 10' 'acrx -o comm,ruid,%cpu' '-t1 10 1' '-f -pfc /var/db/r*/com.apple.*.{BS,Bas,Es,OSXU,Rem,up}*.bom' '{/,}L*/Lo*/Diag* -type f -regex .\*[cgh] ! -name *ag \( -exec grep -lq "^Thread c" {} \; -exec printf \* \; -o -true \) -execdir stat -f:%Sc:%N -t%F {} \;|sort -t: -k2 |tail -n'${p[38]} '-L {/{S*/,},}L*/Lau* -type f' '-L /{S*/,}L*/StartupItems -type f -exec file {} +' '-L /S*/L*/{C*/Sec*A,E}* {/,}L*/{A*d,Ca*/*/Ex,Compon,Ex,In,iTu,Keyb,Mail/B,P*P,Qu*T,Scripti,Sec,Servi,Spo,Widg}* -type f -name Info.plist' '/usr/lib -type f -name *.dylib' `awk "${s[31]}"<<<${p[23]}` "/e*/{auto,{cron,fs}tab,hosts,{[lp],sy}*.conf,pam.d,ssh{,d}_config,*.local} {,/usr/local}/etc/periodic/*/* /L*/P*{,/*}/com.a*.{Bo,sec*.ap}*t .launchd.conf" list getenv /Library/Preferences/com.apple.alf\ globalstate --proxy '-n get default' -I --dns -getdnsservers\ "${p[N5]}" -getinfo\ "${p[N5]}" -P -m\ / '' -n1 '-R -l1 -n1 -o prt -stats command,uid,prt' '--regexp --only-files --files com.apple.pkg.*|sort|uniq' -kl -l -s\ / '-R -l1 -n1 -o mem -stats command,uid,mem' -i4TCP:0-1023 com.apple.dashboard\ layer-gadgets '-d /L*/Mana*/$USER&&echo On' '-app Safari WebKitDNSPrefetchingEnabled' );N1=${#c2[@]};for j in {0..8};do c2[N1+j]=SP${p[j]}DataType;done;N2=${#c2[@]};for j in 0 1;do c2[N2+j]="-n ' syscall::'${p[33+j]}':return { @out[execname,uid]=sum(arg0) } tick-10sec { trunc(@out,1);exit(0);} '";done;l=(Restricted\ files Hidden\ apps 'Elapsed time (s)' POST Battery Safari\ extensions Bad\ plists 'High file counts' User Heat System\ load boot\ args FileVault Diagnostic\ reports Log 'Free space (MiB)' 'Swap (MiB)' Activity 'CPU per process' Login\ hook 'I/O per process' Mach\ ports kexts Daemons Agents launchd Startup\ items Admin\ access Root\ access Bundles dylibs Apps Font\ issues Inserted\ dylibs Firewall Proxies DNS TCP/IP Wi-Fi Profiles Root\ crontab User\ crontab 'Global login items' 'User login items' Spotlight Memory Listeners Widgets Parental\ Controls Prefetching );N3=${#l[@]};for i in 0 1 2;do l[N3+i]=${p[5+i]};done;N4=${#l[@]};for j in 0 1;do l[N4+j]="Current ${p[29+j]}stream data";done;A0() { id -G|grep -qw 80;v[1]=$?;((v[1]==0))&&sudo true;v[2]=$?;v[3]=`date +%s`;clear >&-;date '+Start time: %T %D%n';};for i in 0 1;do eval ' A'$((1+i))'() { v=` eval "${c1[$1]} ${c2[$2]}"|'${c1[30+i]}' "${s[$3]}" `;[[ "$v" ]];};A'$((3+i))'() { v=` while read i;do [[ "$i" ]]&&eval "${c1[$1]} ${c2[$2]}" \"$i\"|'${c1[30+i]}' "${s[$3]}";done<<<"${v[$4]}" `;[[ "$v" ]];};A'$((5+i))'() { v=` while read i;do '${c1[30+i]}' "${s[$1]}" "$i";done<<<"${v[$2]}" `;[[ "$v" ]];};';done;A7(){ v=$((`date +%s`-v[3]));};B2(){ v[$1]="$v";};for i in 0 1;do eval ' B'$i'() { v=;((v['$((i+1))']==0))||{ v=No;false;};};B'$((3+i))'() { v[$2]=`'${c1[30+i]}' "${s[$3]}"<<<"${v[$1]}"`;} ';done;B5(){ v[$1]="${v[$1]}"$'\n'"${v[$2]}";};B6() { v=` paste -d: <(printf "${v[$1]}") <(printf "${v[$2]}")|awk -F: ' {printf("'"${f[$3]}"'",$1,$2)} ' `;};B7(){ v=`grep -Fv "${v[$1]}"<<<"$v"`;};C0(){ [[ "$v" ]]&&echo "$v";};C1() { [[ "$v" ]]&&printf "${f[$1]}" "${l[$2]}" "$v";};C2() { v=`echo $v`;[[ "$v" != 0 ]]&&C1 0 $1;};C3() { v=`sed -E "$s"<<<"$v"`&&C1 1 $1;};for i in 1 2;do for j in 2 3;do eval D$i$j'(){ A'$i' $1 $2 $3; C'$j' $4;};';done;done;{ A0;A2 0 $((N1+1)) 2;C0;A1 0 $N1 1;C0;B0;C2 27;B0&&! B1&&C2 28;D12 15 37 25 8;A1 0 $((N1+2)) 3;C0;D13 0 $((N1+3)) 4 3;D23 0 $((N1+4)) 5 4;for i in 0 1 2;do D13 0 $((N1+5+i)) 6 $((N3+i));done;D13 1 10 7 9;D13 1 11 8 10;D22 2 12 9 11;D12 3 13 10 12;D23 4 19 44 13;D23 5 14 12 14;D22 6 36 13 15;D22 7 37 14 16;D23 8 15 38 17;D22 9 16 16 18;B1&&{ D22 11 17 17 20;for i in 0 1;do D22 28 $((N2+i)) 45 $((N4+i));done;};D22 12 44 54 45;D22 12 39 15 21;A1 13 40 18;B2 4;B3 4 0 19;A3 14 6 32 0;B4 0 5 11;A1 17 41 20;B7 5;C3 22;B4 4 6 21;A3 14 7 32 6;B4 0 7 11;B3 4 0 22;A3 14 6 32 0;B4 0 8 11;B5 7 8;B1&&{ A2 19 26 23;B7 7;C3 23;};A2 18 26 23;B7 7;C3 24;A2 4 20 21;B7 6;B2 9;A4 14 7 52 9;B2 10;B6 9 10 4;C3 25;D13 4 21 24 26;B4 4 12 26;B3 4 13 27;A1 4 22 29;B7 12;B2 14;A4 14 6 52 14;B2 15;B6 14 15 4;B3 0 0 30;C3 29;A1 4 23 27;B7 13;C3 30;D13 24 24 32 31;D13 25 37 32 33;A1 23 18 28;B2 16;A2 16 25 33;B7 16;B3 0 0 34;B2 21;A6 47 21&&C0;B1&&{ D13 21 0 32 19;D13 10 42 32 40;D22 29 35 46 39;};D23 14 1 48 42;D12 34 43 53 44;D22 0 $((N1+8)) 51 32;D13 4 8 41 6;D12 26 28 35 34;D13 27 29 36 35;A2 27 32 39&&{ B2 19;A2 33 33 40;B2 20;B6 19 20 3;};C2 36;D23 33 34 42 37;B1&&D23 35 45 55 46;D23 32 31 43 38;D12 36 47 32 48;D13 20 42 32 41;D13 14 2 48 43;D13 4 5 32 1;D22 4 4 50 0;D13 14 3 49 5;D12 26 48 59 49;B3 4 22 57;A1 26 46 56;B7 22;B3 0 0 58;C3 47;D23 22 9 37 7;A7;C2 2;} 2>/dev/null|pbcopy;exit 2>&-

Copy the selected text to the Clipboard by pressing the key combination command-C.

7. Launch the built-in Terminal application in any of the following ways:

• Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
• In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
• Open LaunchPad. Click Utilities, then Terminal in the icon grid.

Click anywhere in the Terminal window and paste by pressing command-V. The text you pasted should vanish immediately. If it doesn't, press the return key.

8. If you see an error message in the Terminal window such as "syntax error," enter

exec bash

and press return. Then paste the script again.

9. If you're logged in as an administrator, you'll be prompted for your login password. Nothing will be displayed when you type it. You will not see the usual dots in place of typed characters. Make sure caps lock is off. Type carefully and then press return. You may get a one-time warning to be careful. If you make three failed attempts to enter the password, the test will run anyway, but it will produce less information. In most cases, the difference is not important. If you don't know the password, or if you prefer not to enter it, press the key combination control-C or just press return three times at the password prompt. Again, the script will still run.

If you're not logged in as an administrator, you won't be prompted for a password. The test will still run. It just won't do anything that requires administrator privileges.

10. The test may take a few minutes to run, depending on how many files you have and the speed of the computer. A computer that's abnormally slow may take longer to run the test. While it's running, there will be nothing in the Terminal window and no indication of progress. Wait for the line

[Process completed]

"CleanMyMac" is a scam. I've found it being distributed through the same channels as the "Genieo" trojan.

The developer's instructions don't completely remove it. Follow those instructions, then do as below.

Back up all data.

Triple-click anywhere in the line below on this page to select it:

/Library/LaunchDaemons/com.macpaw.CleanMyMac2.Agent.plist

Right-click or control-click the highlighted line and select

          Services ▹ Reveal in Finder (or just Reveal)

from the contextual menu.* A folder should open with an item selected. Move the selected item to the Trash. You may be prompted for your administrator login password. Repeat with this line:

/Library/PrivilegedHelperTools/com.macpaw.CleanMyMac2.Agent

Restart the computer and empty the Trash. Never again install "CleanMyMac" or anything like it.

*If you don't see the contextual menu item, copy the selected text to the Clipboard by pressing the key combination  command-C. In the Finder, select

          Go ▹ Go to Folder...

from the menu bar and paste into the box that opens by pressing command-V. You won't see what you pasted because a line break is included. Press return.

How to maintain a Mac

1. Make two or more backups of all your files, keeping at least one off site at all times in case of disaster. One backup is not enough to be safe. Don’t back up your backups; all should be made directly from the original data. Don’t rely completely on any single backup method, such as Time Machine. If you get an indication that a backup has failed, don't ignore it.

2. Keep your software up to date. In the App Store or Software Update preference pane (depending on the OS version), you can configure automatic notifications of updates to OS X and other Mac App Store products. Some third-party applications from other sources have a similar feature, if you don’t mind letting them phone home. Otherwise you have to check yourself on a regular basis.

Keeping up to date is especially important for complex software that modifies the operating system, such as device drivers. Before installing any Apple update, you must check that all such modifications that you use are compatible. Incompatibility with third-party software is by far the most common cause of trouble with system updates.

3. Don't install crapware, such as “themes,” "haxies," “add-ons,” “toolbars,” “enhancers," “optimizers,” “accelerators,” "boosters," “extenders,” “cleaners,” "doctors," "tune-ups," “defragmenters,” “firewalls,” "barriers," “guardians,” “defenders,” “protectors,” most “plugins,” commercial "virus scanners,” "disk tools," or "utilities." With very few exceptions, such stuff is useless or worse than useless. Above all, avoid any software that purports to change the look and feel of the user interface.

It's not much of an exaggeration to say that the whole "utility" software industry for the Mac is a fraud on consumers. The most extreme examples are the "CleanMyMac," "TuneUpMyMac," and “MacKeeper” scams, but there are many others.

As a rule, you should avoid software that changes the way other software works. Plugins for Photoshop and similar programs are an obvious exception to this rule. Safari extensions, and perhaps the equivalent for other web browsers, are a partial exception. Most are safe, and they're easy to get rid of if they don't work. Some may cause the browser to crash or otherwise malfunction. Some are malicious. Use with caution, and install only well-known extensions from relatively trustworthy sources, such as the Safari Extensions Gallery.

The only software you should install is that which directly enables you to do whatever you bought the computer to do. For example, a word processor is useful for writing. A video editor is useful for making movies. A game is useful for having fun. But a "cache cleaner" isn't useful for anything. You didn't buy the computer to clean caches.

Never install any third-party software unless you know how to uninstall it. Otherwise you may create problems that are very hard to solve. Do not rely on "utilities" such as "AppCleaner" and the like that purport to remove software.

4. Don't install bad, conflicting, or unnecessary fonts. Whenever you install new fonts, use the validation feature of the built-in Font Book application to make sure the fonts aren't defective and don't conflict with each other or with others that you already have. See the built-in help and this support article for instructions. Deactivate or remove fonts that you don't really need to speed up application launching.

5. Avoid malware. Malware is malicious software that circulates on the Internet. This kind of attack on OS X was once so rare that it was hardly a concern, but malware is now increasingly common, and increasingly dangerous.

There is some built-in protection against malware, but you can’t rely on it—the attackers are always at least one day ahead of the defense. You can’t rely on third-party protection either. What you can rely on is common-sense awareness—not paranoia, which only makes you more vulnerable.

Never install software from an untrustworthy or unknown source. If in doubt, do some research. Any website that prompts you to install a “codec” or “plugin” that comes from the same site, or an unknown site, is untrustworthy. Software with a corporate brand, such as Adobe Flash Player, must come directly from the developer's website. No intermediary is acceptable, and don’t trust links unless you know how to parse them. Any file that is automatically downloaded from the web, without your having requested it, should go straight into the Trash. A web page that tells you that your computer has a “virus,” or that anything else is wrong with it, is a scam.

In OS X 10.7.5 or later, downloaded applications and Installer packages that have not been digitally signed by a developer registered with Apple are blocked from loading by default. The block can be overridden, but think carefully before you do so.

Because of recurring security issues in Java, it’s best to disable it in your web browsers, if it’s installed. Few websites have Java content nowadays, so you won’t be missing much. This action is mandatory if you’re running any version of OS X older than 10.6.8 with the latest Java update. Note: Java has nothing to do with JavaScript, despite the similar names. Don't install Java unless you're sure you need it. Most people don't.

6. Don't fill up your disk/SSD. A common mistake is adding more and more large files to your home folder until you start to get warnings that you're out of space, which may be followed in short order by a startup failure. This is more prone to happen on the newer Macs that come with an internal SSD instead of the traditional hard drive. The drive can be very nearly full before you become aware of the problem.

While it's not true that you should or must keep any particular percentage of space free, you should monitor your storage use and make sure you're not in immediate danger of using it up. According to Apple documentation, you need at least 9 GB of free space on the startup volume for normal operation.

If storage space is running low, use a tool such as OmniDiskSweeper to explore the volume and find out what's taking up the most space. Move seldom-used large files to secondary storage.

7. Relax, don’t do it. Besides the above, no routine maintenance is necessary or beneficial for the vast majority of users; specifically not “cleaning caches,” “zapping the PRAM,” "resetting the SMC," “rebuilding the directory,” "defragmenting the drive," “running periodic scripts,” “dumping logs,” "deleting temp files," “scanning for viruses,” "purging memory," "checking for bad blocks," "testing the hardware," or “repairing permissions.” Such measures are either completely pointless or are useful only for solving problems, not for prevention.

To use a Mac effectively, you have to free yourself from the Windows mindset that every computer needs regular downtime maintenance such as "defragging" and "registry cleaning." Those concepts do not apply to the Mac platform.

A well-designed computing device is not something you should have to think about much. It should be an almost transparent medium through which you communicate, work, and play. If you want a machine that needs a lot of attention, use a PC.

The very height of futility is running an expensive third-party application called “Disk Warrior” when nothing is wrong, or even when something is wrong and you have backups, which you must have. Disk Warrior is a data-salvage tool, not a maintenance tool, and you will never need it if your backups are adequate. Don’t waste money on it or anything like it.