Any valid filename suffix can be used. We generally default to .drawio, if you want a recommendation, use that.
Extensions are optional, we select the extension ".drawio" by default, which saves in the default XML diagram data format. If you change the extension to one of the following, you will get special behaviour:
- .svg causes file to save as SVG with embedded data. That is, it's an SVG image, but you can reload the file back into draw.io and edit as if it were a diagram file.
- .png causes file to save as PNG with embedded data. That is, it's a PNG image, but you can reload the file back into draw.io and edit as if it were a diagram file.
- .html causes file to save as HTML with redirect to cloud URL. This means an HTML file is created that contains the diagram data. The HTML file also stores the URL to load the actual file. So, for example, say the file is stored in Google Drive. The HTML page, when loaded, will redirect to the www.draw.io#G..... URL that is the actual diagram loaded from Google Drive.