Why is my cursor jumping around?

See -> Trackpad or Magic Trackpad is jumpy or erratic.

It may offer some help.

Clinton

MacBook Pro (15-inch Late 2011), OS X 10.??, 16GB Crucial RAM, Crucial M500 960GB SSD, 27” Apple Thunderbolt Display

There are several possible causes for this issue. Please take each of the following steps that you haven't already tried until it's resolved. Some may not apply in your case.

1. Follow the instructions in this support article, and also this one, if applicable. A damaged or defective AC adapter could be the cause, even if it's the right kind.

2. Press down all four corners of the trackpad at once and release. If there's any effect, it's likely to be temporary, and in that case the unit must be serviced or replaced.

3. Open the Bluetooth preference pane in System Preferences and delete all pointing devices other than the trackpad, if applicable. Disconnect any USB pointing devices. By a "pointing device," I mean a peripheral that moves the cursor, such as a trackpad, mouse, trackball, or graphics tablet. A plain keyboard is not a pointing device.

4. Start up in safe mode and test, preferably without launching any third-party applications. If you don't have the problem in safe mode, but it comes back when you restart as usual, stop here and post your results. Do the same if you can't start in safe mode. If there was no difference in safe mode, go on to the next step.

5. Reset the System Management Controller.

6. If you're using a Bluetooth trackpad or mouse, investigate potential sources of interference, including USB 3 devices.

7. A swollen battery in a portable computer can impinge on the trackpad from below and cause erratic behavior. If you have trouble clicking the trackpad, this is likely the reason. The battery must be replaced without delay.

8. There's a report that a (possibly defective) Thunderbolt Ethernet adapter can cause the built-in trackpad of a MacBook to behave erratically. If you're using such an adapter, disconnect it and test.

9. There's also a report of erratic cursor movements caused by an external display that was connected but not turned on.

10. If none of the above applies, or if you have another reason to think that your computer is being remotely controlled, remove it from the network by turning off Wi-Fi (or your Wi-Fi access point), disconnecting from a Bluetooth network link, and unplugging the Ethernet cable or USB modem, whichever is applicable. If the cursor movements stop at once, you should suspect an intrusion.

11. Make a "Genius" appointment at an Apple Store to have the machine and/or external trackpad tested.

Here is what I did to solve the problem, which occurred for me when using a second larger monitor attached to my Macbook Pro. Some combination of something here worked.

Ran disk utility.

Plugged usb optical mouse into computer, as opposed to hub.

Cleaned bottom of mouse.

in system preferences, turned off bluetooth and in mission control, unchecked all boxes.

slowed down tracking and double-click speed.

on laptop, pressed all four corners of trackpad at same time.

My mouse is now stable.

if you are using a second monitor, remember not to let your hand idly sit on the trackpad it does mess with that cursor.

Good luck.

Hi there,

My cursor has been doing all sorts of crazy for about a week and a half. Back story: I bought a very lightly used 2011 MacBook Pro off a friend, who had wiped everything and re-installed Yosemite. It worked fine when I first got it, and when I first loaded everything from my hard drive on, but a few days in the cursor started jumping around, highlighting things it wasn't supposed to, focusing on things it shouldn't, etc. Being a total bother. This continued even when I used a USB mouse (which had worked before on an old computer who had the same problem). I took it to a local computer repair shop (we don't have an Apple store for miles and miles around) and they checked the track pad and said there was nothing wrong, and checked my computer and hard drive for viruses--apparently nothing. It worked fine for a day and then started up again. I've tried everything--pressing on all four corners of the track pad (which made things much worse), making sure there's no liquid or other external interference (when I wipe the track pad, that makes it function for about three seconds), turning off Bluetooth, turning off Wifi (which does make it work), and starting it in SafeMode. It's not the charger either, as this happens both when the computer is plugged in (and regardless of the plug), and when it's not. As for SafeMode, the cursor did work fine then, but it works sporadically anyways (as I type, for example, I have no problem with it--but it may start acting up again at any time), so I'm not sure if this is indicative of anything (same with Wifi--when it's off, the track pad works fine, but I spend much of my time on Wifi so I'm not sure if those few hours without it was just a fluke). In SafeMode, the computer would flash every once in a while, for example when loading a new page (little streams of white would run down my page for a second or two--looking like an old school computer would when it would start up, a la 1995). But maybe that's normal?

I'm a bit at a loss here, other than to uninstall everything and re-install. It's getting worse by the day and makes it really hard to work. And it's also much, much worse in the mornings.

Any thoughts?