SSIM Compress for WordPress
A drop‑in WordPress plugin that puts every JPG and PNG on your site through SSIM‑targeted compression — in the background, with retries, and without you having to babysit it.
SSIM Compress v1.0.5
~30 KB · WordPress 5.5+ · PHP 7.4+ · Single‑site & multisite
What it does
- Sends every JPG/PNG in your media library through the SSIM Compress API and writes the smaller version back over the original.
- Regenerates WordPress thumbnails from the compressed original automatically (or, optionally, sends each thumbnail size through the API for maximum savings).
- Auto‑optimises newly uploaded images.
- Bullet‑proof background runner: classifies failures, retries transient errors with backoff, auto‑pauses on outages, recovers stale claims, never gets stuck on a poison‑pill image.
- Optional bulk‑restorable backups grouped by day, week, or month.
Install
- Download the .zip above.
- In WordPress: Plugins → Add New → Upload Plugin → choose the .zip → Install Now.
- Activate it. For multisite, you can either per‑site activate or Network Activate — when network‑activated, settings and the queue are shared across all subsites and per‑site dashboards show a notice pointing to the network admin.
- Open the SSIM Compress menu, paste your API key (get one from your dashboard), click Test connection.
- Click Start scan to add every existing image to the queue. The progress bar shows totals — no need to list thousands of files.
How the queue works
- Batch size (default 1) and delay between batches (default 3 s) control how fast images go through. Newest images first.
- WordPress cron (default) fires roughly every minute on pageviews. For low‑traffic sites, switch to External cron and paste the displayed URL into your host’s cron jobs for guaranteed‑on‑schedule processing.
- Pause/Resume is a single button. The queue also auto‑pauses (5 min) if the SSIM API is unreachable or rate‑limited, and resumes itself.
- An image that fails with a permanent error (corrupt, wrong type, too large for the API) is marked as permanently skipped and never retried. Transient errors retry up to 3 times with backoff.
Backups & restore
Backups are off by default. When you enable them, every original is copied to /wp‑content/uploads/ssim‑backups/ before compression. The Backups tab lists groups by date — one click restores or deletes an entire group.
External cron
If WordPress cron isn’t reliable on your host (low traffic, aggressive caching), enable External cron in Settings and add this to your hosting panel:
* * * * * curl -fsS "https://your-wordpress-site.com/?ssim_cron=YOUR_TOKEN" > /dev/null 2>&1
The plugin will show the exact URL with your unique token in the settings.