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Extensions 
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Transfer Dropbox to Google Drive
Directly transfer files from Dropbox to Google Drive and vice versa. No download and re-upload.
YouTube Uploader for Dropbox, Drive
This app allows you to upload Dropbox, MS OneDrive, Google Drive video files to YouTube directly.
Drive Files to Dropbox™
This app is a file transfer, backup tool for Google Drive. It allow you to save Google Drive's files to Dropbox™ folder directly.
Save Emails to Dropbox by cloudHQ
Save any Gmail email to Dropbox with one click. Autosave of all emails in a label. Multiple export formats: PDF, HTML, TXT, ...
PDF Editor for Drive, Dropbox
Edit PDF files for free for Google Drive, Dropbox. You can add annotate, text, images, form field, freehand, highlight, and more.
File Converter for Drive, Dropbox
Provide a free, simple file converter. Convert any document, archive, spreadsheet, audio and video file from one format to another.
Save web file, URL to Dropbox™
You can save any file from the Internet directly to your Dropbox™ without downloading them to the computer.
Web Clipper for Dropbox
A web clipper tool for Dropbox. Clips web contents directly to Dropbox Paper.