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Detect folders in Safari with HTML5
Safari has limited support for folder detection compared to other browsers. When users drag and drop folders, Safari treats them differently than individual files, which can cause errors during file reading operations.
The Problem with Folders in Safari
When a folder is dropped onto a web page, Safari includes it in the files collection but cannot read its contents using FileReader. This causes the onerror event to trigger, which we can use to detect folder drops.
Folder Detection Method
The following code attempts to read each dropped item as a file. If it's a folder, the FileReader will fail and trigger the error handler:
function handleDrop(e) {
e.preventDefault();
Array.prototype.forEach.call(e.dataTransfer.files, function (file) {
var r = new FileReader();
r.onload = function (event) {
// File read successfully - it's a valid file
console.log("File detected:", file.name);
addFile(file);
};
r.onerror = function (event) {
// Error reading file - likely a folder
alert("Uploading folders isn't supported in Safari browser!");
console.log("Folder detected:", file.name);
};
// Attempt to read the file
r.readAsDataURL(file);
});
}
// Set up drop zone
var dropZone = document.getElementById('dropZone');
dropZone.addEventListener('drop', handleDrop);
dropZone.addEventListener('dragover', function(e) {
e.preventDefault();
});
Complete Example
<!DOCTYPE html>
<html>
<head>
<title>Safari Folder Detection</title>
<style>
#dropZone {
width: 300px;
height: 200px;
border: 2px dashed #ccc;
text-align: center;
padding: 50px;
margin: 20px;
}
</style>
</head>
<body>
<div id="dropZone">
Drop files or folders here
</div>
<script>
function addFile(file) {
console.log("Processing file:", file.name, "Size:", file.size);
}
function handleDrop(e) {
e.preventDefault();
Array.prototype.forEach.call(e.dataTransfer.files, function (file) {
var r = new FileReader();
r.onload = function (event) {
addFile(file);
};
r.onerror = function (event) {
alert("Uploading folders isn't supported in Safari browser!");
};
r.readAsDataURL(file);
});
}
var dropZone = document.getElementById('dropZone');
dropZone.addEventListener('drop', handleDrop);
dropZone.addEventListener('dragover', function(e) {
e.preventDefault();
});
</script>
</body>
</html>
How It Works
The detection relies on Safari's inability to read folder contents:
- File Drop: User drops items onto the drop zone
-
FileReader Attempt: Code tries to read each item using
readAsDataURL() -
Success: If it's a file,
onloadfires and the file is processed -
Error: If it's a folder,
onerrorfires, indicating folder detection
Browser Limitations
| Browser | Folder Support | Detection Method |
|---|---|---|
| Chrome/Edge | Full support | webkitdirectory attribute |
| Firefox | Partial support | File API properties |
| Safari | Limited | FileReader error detection |
Conclusion
Safari's folder detection relies on catching FileReader errors when attempting to read folder contents. While this method works for detection, Safari cannot actually process folder contents like other browsers.
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