Selective Thumbnail Regenerator

The Selective Thumbnail Regenerator plugin provides a powerful and user-friendly way to regenerate image thumbnails for WordPress media libraries. Unlike other thumbnail regeneration plugins that blindly process the entire library, this plugin gives you precise control: choose a specific year, month, and even a title keyword to target exactly the images you need.

Key Features

• Date & Title Filters – Choose a specific year, month, or search by title to target only the images you need.
• Month Status Calendar – Green months are verified full-month, all-size runs with no failures. Legacy records are retained in amber because their scope cannot be verified.
• Regeneration History Tracking – Bounded job summaries store exact filters, selected sizes, counts, and completion status. A “Reset History” button clears all records when needed.
• Thumbnail Size Selection – Choose specific registered thumbnail sizes to regenerate instead of all sizes.
• Configurable Batch Size – Set how many images are processed per AJAX request (1-20).
• Throttle Delay Control – Set a cooldown pause between batches (0-2000 ms) to reduce server load.
• Dry Run Mode – Verify that matching sources exist, are readable, and can be opened without writing changes.
• Stable Server Jobs – User-scoped transient jobs use a fixed upper attachment ID and ID cursor to avoid duplicate or endless offset processing.
• Reload Recovery – Reopen the plugin page within 24 hours to resume an unfinished job from its last per-image checkpoint or cancel it safely.
• Smart Regeneration – Paginated preflight analysis finds missing, dimensionally incorrect, and stale sizes, estimates output size, and regenerates only that subset.
• Automatic Batch Failure Recovery – Progress is checkpointed before every image. Interrupted jobs retry one image at a time and continue safely.
• Failed Images Log – Detailed table of all failed images including ID, title, and exact failure reason.
• Safe Orphaned File Cleanup – Obsolete thumbnails are deleted only after replacement files and metadata are saved successfully.
• Live Terminal Activity Log – Real-time monospace console with timestamped status messages.
• Visual Completion Metrics – Five-card summary board: Processed, Successful, Failed, Skipped, Duration.
• Cancel Support – Stop safely after the current server step and receive an accurate partial summary.
• Performance Optimized – Direct indexed SQL query for year selector loading.

Usage

1. Navigate to Tools > Selective Thumbnail Regenerator.
2. Select a year from the dropdown. A Month Status Calendar will appear showing which months have already been regenerated.
3. Optionally select a month – via the dropdown or by clicking a month badge on the calendar.
4. Optionally enter a title keyword to filter images by name.
5. Adjust batch size and throttle delay in the Performance Configuration card.
6. Enable Dry Run Mode to preview results without making changes.
7. Click “Scan Matching Images” to count matching images. Smart Regeneration performs a paginated preflight and estimates the required thumbnail work and output size.
8. Click “Start Regeneration” to begin. Watch the live terminal log for real-time updates.
9. Review the Job Completion Report and Failed Images Log after the process ends.

Troubleshooting

“No images found for the selected period”

There are no image attachments uploaded during the selected year/month. Try a different time period.

The process is slow

Reduce the throttle delay or increase the batch size if your server can handle more load. Alternatively, increase the delay and reduce batch size if you are getting timeouts.

A batch keeps failing

Enable Dry Run Mode first to verify image accessibility. If specific images crash the server, they will appear in the Failed Images Log after regeneration completes.