UFO - Best practices and Limitations

The Universal File Opener or UFO is a Google Chrome extension. It enhances the Google Drive interface by allowing you to:

  • open the non-Google files locally on your computer in the corresponding application.
  • save the changes you have made locally on your computer directly in Google Drive.

This article give you additional information and best practices when using the UFO:

 General considerations
 Focus on the Local Storage
 Using Adobe Acrobat Reader DC with UFO
 Editing files with external references
 Simultaneous Editing

General considerations

  • When opening the file locally, it is first downloaded in the back-end. The download time depends on the size of the file and your internet bandwidth.
  • If you have not define any application on your computer to open a specific type of file, you will have to select another application.
  • If you have “read-only” access to the file, you will be able to open it but only save it locally.
  • If you want to save it in Acrobat Reader form, you will have to select the destination directory.
    Learn more here: Using Adobe Acrobat Reader DC with UFO on PC
  • If you are not allowed to copy, print or download the file, you will not be able to download it. You will be informed with a notification.

Focus on the Local Storage

When opening a file via the UFO extension, this file is stored in a local repository known as “Local Storage”:

  • If you open a stored file that has not been edited by another user, the file will be opened directly from your “Local Storage”.
  • If you open a stored file that has been edited by another user, the file will be downloaded once more to “Local Storage”.

The “Local Storage” is displayed in the extension page of the UFO extension .


You have access to:

  • “Files stored”: This option displays the number of files opened and automatically stored in the “Local Storage”.
  • Storage used:” This option displays the size of the “Local Storage”.

By clicking “Show more details”,  you can display all files stored and delete them to clear the cache.

When clicking on the file name, you will open the file directly in from the local storage (the file will not be opened from Google Drive).

The action are displayed when hovering over the file:

 image5.png   Opens the Google Drive Folder where the file is located.
2017-05-04_11-32-21.png Displays the information about the locally stored file.
image7.png Deletes the file from the local storage.

The default location for the “Local Storage” are:

On PC C:\Users\<LocalUser>\.syncclient\<uniqueID>\youremailaddress@domain.com
On Mac /Users/<LocalUser>/.syncclient/<uniqueID>/youremailaddress@domain.com

Local storage cleaning

  • The local storage allows a maximum of 100 files. The cleanup is performed when the extension is initialized. If the user opens more files without refreshing its page, the files won’t be removed.
  • If the modification date of the last modified file is more than 30 days, the whole user's local cache will be deleted.

File type opening restriction

If you try to open some file types, the UFO button might not be displayed or a notification could appears to inform you about the extension.

UFO button will be not displayed for the following extensions:

.ahk  .bat  .cmd  .com .csh  .exe  .ksh  .lnk  .msc  .msi  .ps1  .py  .reg  .scr  .sh  

The notification  “The file ‘$filename$’ is an executable and will run a command when opened, do you want to continue?” will appear before the editing:

.action .ins .pif .shb .workflow
.app .isu .potm .shs .ws
.as .job .ppam .tlp .wsf
.command .jse .ppsm .u3p .wsh
.crt .msp .pptm .vb .xap
.docm .mst .prg .vbe .xlam
.dotm .osx .reg .vbs .xlm
.gem .otm .scr .vbscript .xlsm
.inf .paf .sct .wiz .xltm


Important: This is not an exhaustive list and the notification could appear for all types of executable files.

Using Adobe Acrobat Reader DC with UFO

When saving a PDF file after modifications, Adobe Acrobat Reader DC prompts you for the location where you want to save the file.

The current folder of the file you are editing is not selected by default, so it will require you to navigate and select the "Local Storage" location every time you save a document.

This is a default behavior of Adobe Acrobat Reader DC and it is not related the UFO (you would get the same prompt for any file you edit locally).


To allow the UFO to work directly, disable the following setting:

1. Click on Edit > Preferences menu.

2. Go to General section.

3. Disable “Show online storage when saving file”.


After this setting is disabled, you will get a simple prompt, and Clicking on “Save” will update the file in Drive using UFO immediately.


Note: Other PDF reading softwares, like Foxit Reader (free) or Acrobat Reader Pro DC (paying) don’t have this limitation, and will save the file to its current location without prompting the user.

Editing files with external references

Some file formats, like Office formats (Excel external references) or AutoCAD (xref) allow to set references to external files.

This use case is not supported by UFO at the moment, so you will get errors when trying to open such files that were created with external references.

Simultaneous Editing

Currently, UFO does not lock a file when a user starts editing it. However, it detects concurrent modifications of the same file by multiple users, and will prompt the user that a file was modified by another user since it was opened, and ask how to fix the conflict. 

If you want to save a file that has been edited and saved by another user, you may encounter a conflict on this file.


You will have to choose between:

  • Update in Drive with your modified version”: This option allows you to save your changes and delete the previous ones.
  • Discard your changes and get the latest version from Drive”: This option allows you to cancel your changes and keep the current version from Google Drive.

We are working on a real lock feature, that would prevent the situations where two users edit the same file at the same time. It should be available in a near future.

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