Hi @connelsey. Unlike the desktop Arduino IDE, the Arduino Web Editor has every one of the ~4000 libraries of the Arduino Library Manager pre-installed. So it actually has immensely more "library access" out of the box.
However, not all Arduino libraries are in the Library Manager. That is likely the case with the library that provides the SR04.h file on your desktop. In this case, you will need to install the library, just like you needed to install the library to use it on your desktop.
In Arduino Web Editor, installing additional libraries can be done by following these instructions:
- Download the
.zipof the library you want to install, or zip the library from your computer if that's more convenient. - Select "Libraries" from the menu on the left side bar of the web page.
- In the libraries pane that opened, click the upward pointing arrow button ("Import").
- If you get a dialog about importing your sketchbook, click the IMPORT button (though you might like to consider the option of importing your sketchbook).
- From the "Open" dialog that opens, select the
.zipfile of the library. - Click the Open button.
- Wait for the import to finish.