Google Drive offers folders (or collections) for organizing your files but doesn’t support labels or tags. A disadvantage with folders is that a file can only belong to a single folder while multiple #tags, as in Gmail, can be assigned to a single file.
There’s a workaround though. You can assign tags to a file in Google Drive by adding them to the description of a file. A Google forum user has written this Google Script that takes the folder name in which a file is found and assigns those names as tags to the file. It works for nested folders too.
/* setDescriptionToFolderNames Workaround to fake Tags in Google Drive. Writes all the folder names of a file into the file description, so that the file can be found by searching the folder names. */ function setDescriptionToFolderNames() { var file; var filename; var folders; var filedescription; var contents = DocsList.getAllFiles(); // sort ascending. Oldest first, in case of timeout: contents.sort(function(a,b) {return a.getLastUpdated()-b.getLastUpdated()}); // synchronize folder names of all files (only updates if folders have changed): for (var i = 0; i < contents.length; i++) { file = contents[i]; try { filename = file.getName(); //Logger.log("Checking: " +filename +" ("+file.getLastUpdated()+")"); folders = file.getParents(); // sort by folder name: folders.sort(function(a, b) { return a.getName().localeCompare(b.getName()); } ); filedescription = ""; for (var f = 0; f < folders.length; f++) { filedescription = filedescription+folders[f].getName()+" "; } if (filedescription != contents[i].getDescription()) { file.setDescription(filedescription); Logger.log("Updated: " +filename); } } catch(e){ Logger.log("Error: " +filename+" "+e); } } };