A BUP file is a backup copy that certain programs create automatically to protect your work

A BUP file is a hidden backup file that software creates while you are working on a document or project. The ".bup" extension stands for backup. When you open a file in a program like Microsoft Word, Adobe Premiere, or DaVinci Resolve, the software writes a BUP file to your hard drive in the background — usually in the same folder as your original file, or in a temporary folder. If your program crashes, your computer loses power, or you close the file without saving, the BUP file lets you recover most or all of your work.

The BUP file is not the same as your actual document. It is a separate copy that updates as you work. You cannot open it directly in most cases — the program that created it knows how to read it and restore it. BUP files are usually hidden by default, so you may never see them unless you turn on the option to show hidden files in your operating system.

Key Takeaways

  • BUP files are automatic backups created by software while you work, stored separately from your main document.
  • If your program crashes or closes unexpectedly, the software can recover your work from the BUP file when you reopen it.
  • BUP files are hidden by default and cannot be opened directly — only the program that created them can read and restore them.
  • You can safely delete BUP files if you have saved your work, but keeping them costs only a small amount of disk space.
  • Different programs use different names for backup files — Word uses ".wbk", Premiere uses ".bup", and others may use ".tmp" or ".bak".

How BUP files work during your editing session

When you open a document in a program, the software creates a BUP file when ready. As you type, edit, or make changes, the program writes those changes to the BUP file at regular intervals — often every few seconds or every time you pause typing. Your original file stays untouched until you click Save. This means the BUP file is always slightly ahead of what you would recover if something went wrong, but it is not a perfect copy of every keystroke.

The timing matters. If you have been working for 30 minutes and the program crashes, you might recover 29 minutes of work from the BUP file, losing only the last minute. If you crash when ready after opening the file, the BUP file may be nearly empty. The software balances between protecting your work and not slowing down your computer by writing to disk too often.

When you save your document normally, the program writes your changes to the main file and usually deletes or clears the BUP file. When you close the program, it cleans up any BUP files it created. The next time you open the document, a fresh BUP file starts.

What happens when software crashes or closes unexpectedly

If your program crashes, your computer loses power, or you force-close an process, the BUP file is left behind on your hard drive. The next time you open that program and try to open the same document, the software detects the BUP file and offers to recover your work. In Microsoft Word, you see a "Document Recovery" pane on the left side. In Adobe Premiere, a dialog box asks whether you want to recover the project. You can choose to restore from the backup or discard it and open the original file as it was last saved.

Recovery is not always perfect. The BUP file may be corrupted if the crash happened while the software was writing to it, or it may be missing the very last changes you made. But in most cases, you recover the majority of your work. Some programs let you choose between the recovered version and the original, so you can compare them before deciding which to keep.

Where BUP files are stored on your computer

BUP files are usually stored in the same folder as your original document, but some programs hide them in a temporary folder instead. Microsoft Word stores backup files in the same directory as the document, with a name like "Backup of [document name].wbk". Adobe Premiere stores BUP files in the same folder as your project file. DaVinci Resolve uses a folder called "DaVinci Resolve Backups" inside your project folder.

Because BUP files are hidden by default, you may not see them even if they exist. On Windows, you can show hidden files by opening File Explorer, clicking the View tab, and checking "Hidden items". On Mac, press Command + Shift + Period in Finder to toggle hidden files on and off. Once you can see them, BUP files appear with a ".bup", ".wbk", ".tmp", or ".bak" extension depending on the program.

How much disk space BUP files use

A BUP file is roughly the same size as your original document. If you are editing a 5 MB Word document, the backup file is also about 5 MB. If you are working on a video project with a 50 MB project file, the BUP file is also around 50 MB. The total disk space used is usually not a problem unless you work with very large files or have limited storage.

BUP files are cleaned up automatically when you save and close your document normally. They only accumulate if you crash repeatedly without saving, or if you force-close programs without letting them shut down properly. If you are running low on disk space and you see many old BUP files, you can delete them safely — but only if you have already saved the documents they belong to.

Deleting BUP files safely

You can delete BUP files without harming your work, as long as you have saved your main document. If you have a file called "report.docx" and you see "Backup of report.wbk" in the same folder, the WBK file is safe to delete. The original DOCX file is unaffected. Deleting a BUP file only removes the recovery option — it does not touch your actual work.

The safest time to delete BUP files is after you have closed the program and confirmed that your document saved correctly. Do not delete a BUP file while the program is still running, because the software may try to write to it and cause an error. If you want to clean up old backup files regularly, you can set up your operating system to delete files older than a certain date, or you can delete them manually from the folder where they are stored.

Different programs, different backup file names

Not all backup files use the ".bup" extension. Microsoft Word uses ".wbk" for backup files. Adobe Premiere uses ".bup". DaVinci Resolve uses ".bak". Some programs use ".tmp" for temporary backup files. Knowing which extension belongs to which program helps you identify what you are looking at when you see hidden files on your hard drive.

Some programs also create multiple backup versions, keeping the last few saves instead of just one. DaVinci Resolve, for example, can create numbered backup files like "project_backup_001.bak", "project_backup_002.bak", and so on. This gives you more recovery options if something goes wrong. You can usually control how many backups a program keeps through its preferences or settings menu.

Frequently Asked Questions

Can I open a BUP file directly?

No, not in most cases. BUP files are in a format that only the program that created them can read. If you try to open a BUP file in Notepad or another program, you will see garbled text. The only way to use a BUP file is to let the original program recover it automatically when you reopen the document after a crash.

What if I want to keep a backup file instead of the original?

When recovery is offered, most programs let you choose which version to keep. You can select the recovered version and save it with a new name, or you can save it over the original file. After you make your choice, the BUP file is deleted. If you want to keep both versions, save the recovered file with a different name before closing the recovery dialog.

Do BUP files slow down my computer?

No, BUP files have minimal impact on performance. The software writes to them in the background while you work, and the delay is not noticeable. The only time you might see a slowdown is if your hard drive is very full or very slow, but even then the effect is small.

What if I see a BUP file for a document I deleted?

If you deleted the original document but the BUP file remains, you can delete the BUP file too. It is no longer useful because the program cannot recover a document that no longer exists. You can safely remove it to free up disk space.

Can I recover a document from a BUP file if I did not crash?

Not easily. BUP files are designed for crash recovery, and most programs only offer recovery when they detect an unexpected shutdown. If you closed a document normally and want to recover an earlier version, you need a different backup method — like using your operating system's file history, cloud storage versioning, or a dedicated backup program.