Undo your Mistakes!

Sometimes we make mistakes.  Fortunately, sometimes we can undo our mistakes.   Undo is a command or option in many computer or phone programs that undoes the last change made,  reverting the data or program to its state before the change was made.

The opposite of undo is redo. The redo command undoes the last undo. Both undo and redo are available in almost all computer software today.

Below are some ways to undo some of your technology mistakes.

General Undo Functionality

Many programs have a generic undo functionality built in.  It can usually be accessed via the program's menu (usually as an Edit option) or via an icon in the program's tool bar (usually as curved arrow pointing left) or via  a keyboard shortcut (often the most convenient way to undo something).

In most Windows applications, the undo command can be activated by pressing the Ctrl + z (or sometimes the Alt + Backspace) key combination. In most Macintosh applications, the undo command can be activated by pressing the Command + z key combination. 

The common command combination for redo on Windows applications is Ctrl + y or Ctrl + Shift + z. The common command combination for redo on Macintosh applications is Command + Shift + z.

Most times, you can undo or redo multiple times, to revert or restore multiple changes until you get the program or data back to the desired state.  Keep in mind that programs generally keep track of your previous changes only for as long as that program or file is open. If you close the file or program and open it again, you won’t be able to undo previous changes.

In Windows, you can even undo things like a file rename or move using the Ctrl + z key combination.

Accidentally Closed a Browser Tab

In many browsers, you can re-open the most recently closed tab by using the keyboard shortcut key combination Ctrl + Shift + t (on Macs use Command + Shift + t).

Accidental Changes on your Phone or Tablet

On Apple iPhones, you can usually shake your phone to activate the undo feature in a text program. Simply shake your iPhone or iPad quickly. Doing so opens a dialog box asking if you want to "Undo" the action you had just performed.  If you shake it after doing an undo, shaking it again will allow you to perform a redo.

Unfortunately, without installing a third party app, there doesn't appear to be a way to undo mistakes on  Android-based phones. However, you can install an app such as "Inputting+" to give your apps the ability to undo under Android.

Accidentally deleted a file

Sometimes you can "undelete" a file in Windows via Ctrl + z.  This works because often the file wasn't actually deleted, but just moved to the Trash folder.

In Windows, Macintosh and Linux, you might be able to manually restore files moved to the trash also by navigating to your Trash folder, finding the file, and moving it back to the proper location (or right-clicking on the file and selecting "Restore").

If you delete a file that you wish to restore, we hope that you are running a backup program like UT Backup or Shadow Copy on Windows. If so, you might be able to restore a (possibly older) copy of the file from your last backup.

Sometimes the file, or an older version of it, may be lying around somewhere without your knowing about it.  On Windows, some applications will save copies of your documents in the Temp folder on your computer. To find your Temp folder, search for "Temp" (or go to Windows Explorer, and go to the path C:\Users\<username>\AppData\Local\Temp  in your navigation bar, where  “<username>” is your login name for the computer.  On Linux, the file might be in your system's /tmp/ directory, so it is worth checking there for it.  If the document was downloaded or accessed from the web, also check your Downloads folder.  This is typically where any downloaded files are saved.

If none of the above methods work, as a last resort try searching for the file by its contents.  In Windows, click the Start Menu and select “search programs and files” at the bottom.  On Macintosh, use your Spotlight tool – the little magnifying glass at the top right of your Folder windows.  Put in any word or phrase that is in the lost document.  This will search your hard drive and return a list of documents that contain the words you entered.   This method is also very handy when you’re looking for an old document and you can’t remember what you named it or where you put it.

If none of the above work,  usually the only way to recover it is using a third party application or service designed for this purpose.  If so, speed is of the essence, and you should stop using your computer immediately, as the more you use your computer in such a case the lower the chance of recovery.  Such a discussion in beyond the scope of this blog article; but if you need help in such a case, you can contact the CNS Help Desk at https://cns.utexas.edu/help/

Accidentally Sent an E-Mail

If you are using Microsoft Office 365, you can't unsend a message, but you can try to recall it in some cases.

With message recall, the message is retrieved from the mailboxes of any other Office 365 recipients within UT who haven’t yet opened it. You can also substitute a replacement message (for example, if you forgot to include an attachment, you can try to retract the message, and then send a replacement message that has the attachment.)  Message recall will not work for messages sent outside of Office 365, or to those outside of UT.

If you use UT Mail or gmail,  you can configure it to allow a very limited window to unsend a message.  It isn't enabled by default, so first, you have to set it up:

  • Click Settings (the little gear icon on the upper right)
  • Choose General (the first item in the list of selections in blue type across the top)
  • Look for Undo Send and click Enable Undo Send
  • Select the number of seconds delay you will have to Undo a send (from 5 to 30 seconds)
  • Scroll all the way down and click Save Changes.

Once setup, you have at least 5 seconds and up to 30 seconds to unsend the email; you’ll see an “Unsend” link in the “Email sent” notification that appears after you hit send; just click on that link to unsend it.  Unfortunately, after the number of seconds selected, the email is sent; and you can't get it back anymore.

Undo a Software Update

If you install a software update and it causes problems, you can usually undo the update in several ways.

If you are using Windows, you can use System Restore to restore from a previous restore point.  This reverts your operating system (but not your documents and files) to the state it was in at the time the restore point was made.  Once the update that caused the problem is identified, you can blacklist it so it never gets applied, and allow it to install all other updates so your system isn't vulnerable to attack.

Many Virtual Machines allow you to create Snapshots or Restore Points as well, which you can revert back to.  However, unlike the Windows System Restore, going back to a Virtual Machine snapshot or restore point usually restores everything including your documents and files to the previous state!

In Windows, you can remove an individual Microsoft Update that is causing problems also.  In theory, it is as simple as going to the Control Panel section called "Programs and Features", selecting "View Installed Updates", right-clicking on the problematic update, and selecting to remove it.  Of course, you need to identify which update it is first (or you could try removing all updates before a certain date, but this could leave your system vulnerable to attack if you are not careful and don't reapply the other updates).

In RHEL based Linux releases which use "yum" for updates, you can reverse a "yum upgrade" using "yum downgrade" to revert to the previous package release.  You can find a time-stamped list of updated packages in /var/log/yum.


The above list is not a complete list of ways to undo mistakes made on a computer.  If you need additional help, feel free to contact the CNS Help Desk at https://cns.utexas.edu/help/ for assistance.

Written by Eric Rostetter, Senior System Administrator
Questions or comments? The best and easiest way to contact us is via the CNS Help Desk form.