Thumbnail Manager

Thumbnail Manager is a WordPress thumbnail management plugin for regenerating image sizes, preventing thumbnail bloat, and safely cleaning unused generated files from the Media Library.

Use it after changing themes, updating WooCommerce image settings, adjusting registered image sizes, migrating a site, or discovering years of old thumbnail files. Thumbnail Manager lets you decide which sizes WordPress should generate, rebuild missing thumbnails, inspect cleanup candidates, and delete only an explicitly approved manifest.

The plugin is designed for both new sites and large, long-running Media Libraries. Persistent cursor-based jobs process work in batches, survive page reloads or network interruptions, and can be limited to multiple upload years or months.

Key Features

• Regenerate WordPress thumbnails for existing image attachments
• Generate only missing image sizes or force-regenerate selected media
• Disable unwanted registered image sizes for future uploads
• Review recommendations before changing thumbnail settings
• Prune unused thumbnails while preserving the sizes you choose to keep
• Scan first, review an immutable hashed manifest, then approve deletion separately
• Search and select multiple upload years or month folders in one Prune job
• Filter and paginate large deletion manifests with estimated storage totals
• Detect legacy thumbnail sizes stored in attachment metadata
• Report unmapped disk-only orphan files without deleting them by default
• Resume regeneration, recommendation, scan, and delete jobs after interruption
• Review active and recent jobs with retained audit information
• Use responsive admin screens that inherit the user’s WordPress Color Scheme

Safe WordPress Thumbnail Cleanup

Prune Files uses a review-first workflow instead of deleting files immediately:

1. Choose the registered image sizes to keep.
2. Scan all uploads or select multiple year and month folders.
3. Review the immutable manifest and estimated storage total.
4. Confirm the reviewed manifest explicitly.
5. Delete approved generated files in resumable batches.

Original full-size uploads are protected. Paths are validated inside the WordPress uploads directory, and attachment metadata is updated when generated size files are removed.

Built for Large Media Libraries

Thumbnail Manager avoids a single long-running request for large operations. Persistent jobs, cursor-based attachment queries, bounded AJAX batches, folder-limited scans, operation locks, and per-item errors make long media maintenance tasks easier to monitor and resume.

The Prune folder picker groups upload directories by year, supports search and bulk selection, and automatically removes overlapping month selections when an entire year is selected.

WooCommerce and Theme Changes

Thumbnail Manager recognizes WooCommerce-related image sizes in Recommendations and helps you review them before disabling, regenerating, or pruning files. It is also useful after switching themes or removing plugins that registered custom image sizes.

What Thumbnail Manager Does Not Do

• It does not compress or change image quality.
• It does not replace an image optimization, WebP, CDN, or offload plugin.
• It does not delete original uploaded images.
• It does not automatically delete files without manifest review and approval.
• It does not unregister image sizes from the theme or plugin that registered them.

Usage

Recommended Workflow

1. Open Tools > Thumbnail Manager.
2. Run Recommendations and review which sizes appear necessary.
3. Open Thumbnail Sizes and save the sizes WordPress should generate for future uploads.
4. Run Regenerate to rebuild missing or selected thumbnails.
5. Open Prune Files and choose the sizes to keep.
6. Select All uploads or choose multiple upload folders.
7. Scan, review the manifest, and approve deletion only when the result is correct.

Regenerate Thumbnails

Use Regenerate after changing image dimensions, switching themes, changing WooCommerce image settings, migrating media, or restoring missing thumbnail files. Process all image attachments, the current year, a selected uploads folder, or specific attachment IDs.

Only Missing generates absent sub-sizes. Force Regenerate rebuilds metadata and selected sub-sizes from the original image path when WordPress provides one.

Thumbnail Sizes

Use Thumbnail Sizes to control which registered image sizes WordPress should generate for future uploads. Disabling a size does not remove existing files; use Prune Files when you are ready to scan and review old generated thumbnails.

Recommendations

Recommendations reviews registered sizes against protected WordPress sizes, WooCommerce-related sizes, attachment metadata, and common content references. Treat the result as an informed starting point and review it for your theme and site before applying changes.

Prune Files

Choose the image sizes to keep, decide whether to scan all uploads or selected year/month folders, and start Scan. Scanning builds a manifest only. Nothing is deleted until the scan finishes, the manifest is displayed, and an administrator explicitly approves it.

Optional orphan discovery includes metadata-backed legacy sizes in the review. Unmapped disk-only filename matches are reported and skipped by default.

Technical Notes

• Uses intermediate_image_sizes_advanced to control future thumbnail generation
• Uses dedicated persistent job and job-item tables instead of storing full queues in transients
• Uses cursor-based AJAX queues for regeneration, recommendations, pruning, orphan discovery, manifest creation, and deletion
• Separates scan, immutable manifest review, explicit approval, and deletion
• Binds expiring job tokens and manifests to the current site and user
• Supports resume, server-side cancellation, operation locking, cleanup, and per-item error tracking
• Uses attachment metadata as the primary source for prune candidates
• Validates filesystem paths under the WordPress uploads directory
• Updates attachment metadata after generated thumbnail files are removed
• Prefers the original image path during force regeneration when WordPress provides one
• Requires the manage_options capability
• Runs per site on WordPress multisite

Privacy

Thumbnail Manager does not collect, store, or transmit personal data to external services. All thumbnail scans, regeneration, recommendations, and cleanup operations run locally on your WordPress site.