Troubleshooting the “Upload Failed” Error in WordPress: An Expert’s In-Depth Guide

Seeing the “Upload failed to write file to disk” error when trying to add media to your WordPress site is incredibly frustrating. But you’re not alone – a 2019 survey found over 30% of WordPress users have encountered this pesky upload error.

In this comprehensive guide, I’ll leverage my 15 years of experience as a webmaster to walk you through how to troubleshoot and fix the “Upload failed” error in WordPress. Follow these steps and you’ll be uploading images, videos, and docs in no time.

What Causes the “Failed to Write File” Error in WordPress?

Before we dive into solutions, let’s quickly recap what causes this error:

• Incorrect folder permissions – If permissions on key folders like wp-content/uploads are too restrictive, WordPress can’t write files.

• Full temporary folder – WordPress uploads initially go to a temp directory. If it’s full, uploads fail.

• Misconfigured temp folder – An incorrect temp path or permissions can block uploads.

Under the hood, WordPress relies on that temporary folder between when you select a file to upload and when it appears in the Media Library. I’ll share some history on why WordPress’ upload process works this way later on.

Checking and Adjusting Folder Permissions

Folder permissions play a pivotal role in those “failed to write file” errors. Let’s explore how to check and tweak permissions:

Via cPanel

1. Log in to cPanel and open File Manager.
2. Navigate to the wp-content folder.
3. Right click on wp-content and select Change Permissions.
4. For folders, set permissions to 755 recursively.
5. For files, set permissions to 644 recursively.

Via FTP

1. Connect to your site via FTP and navigate to the wp-content folder.
2. Right click on wp-content and click Get Info > Permissions.
3. For folders, set permissions to 755 recursively.
4. For files, set permissions to 644 recursively.

Setting permissions recursively is crucial so they apply to all subfolders and files too.

Here‘s a quick reference table of recommended WordPress folder/file permissions:

File Type	Single Site	Multisite
Folders	755	755
Files	644	644

And don’t forget to double check your FTP user has access to write to that temporary uploads folder.

Ask Your Host to Empty the Temp Folder

If adjusting permissions doesn’t fix the upload error, the next step is to contact your web host and request they empty the temporary folder on the server. This directory can fill up over time with remnants from failed uploads.

You’ll also want to verify the temp folder path configured in wp-config.php is correct.

Additional Troubleshooting Tips from a WordPress Pro

After 15 years resolving upload issues for clients, here are a few other tips I’ve picked up:

• Increase the max file size limit in php.ini if you’re uploading large files.

• Check permissions on parent folders above wp-content, like public_html. Issues can trickle down.

• Make 100% sure your FTP user has access to write to the temporary upload directory.

• Adjust WordPress file size limits in wp-config.php to match your web host’s environment.

• Beware of plugin conflicts where security plugins may block uploads. Temporarily disabling plugins can help diagnose.

• Migrating hosts often causes issues due to permission and path changes. Be vigilant.

A Word on WordPress Security

While permissions of 755 on folders and 644 on files are generally recommended, I advise against setting your wp-content folder to permissions of 777 (public write access). This introduces security risks.

How to Prevent “Failed to Write” Errors in WordPress

A little prevention goes a long way when it comes to avoiding “failed to write file” errors in the future:

• Set proper 755/644 file permissions from the start

• Monitor disk space of your temp directory and clear it out regularly

• Tweak wp-config.php to provide WordPress adequate resources for your site’s size and traffic.

Migrating or setting up a new WordPress site? Be sure to follow detailed best practices to avoid upload issues down the road.

Why Does WordPress Have a Temporary Uploads Folder? A Brief History

If you’re wondering why WordPress doesn’t upload files directly to the uploads folder, a bit of history explains it. Back when WordPress was created in 2003, limitations of PHP and most web hosts required a temp folder to handle file uploads reliably.

As WordPress and web hosting evolved, this temp directory remained the standard approach. It helps ensure a failed upload doesn’t corrupt existing media files. The temp folder stores remnants of failed uploads safely out of the way.

Fixing “Upload Failed” Errors – Recap and Final Tips

Hopefully this guide has given youexpert-level direction on troubleshooting the pesky “Upload failed to write file to disk” error in WordPress. To recap:

• Double check folder permissions and reset to 755/644 if needed.

• Have your host clear out the temporary upload folder.

• Follow other optimization tips to tweak settings.

• Prevent issues by setting up proper file permissions from the start.

Let me know if any part of resolving this common WordPress upload error remains unclear! With the steps in this guide, you should be well on your way to fixing the “Upload failed” error.