EWWW Image Optimizer
EWWW Image Optimizer compresses images server-side and optionally converts them to WebP and AVIF. WP Media Cloud has a dedicated integration with EWWW that coordinates the compression and offload sequence correctly in both synchronous and background modes. EWWW is also the engine behind EWWW Easy IO, which is a separate CDN integration covered in the EWWW Easy IO CDN doc.
How they work together#
WP Media Cloud and EWWW have an active integration — not just passive detection. The upload sequence is coordinated differently depending on which EWWW compression mode you are using.
Synchronous mode (EWWW default)
In synchronous mode, EWWW compresses all image sizes during the WordPress upload process before WP Media Cloud offloads the file. WP Media Cloud hooks into wp_update_attachment_metadata at priority 110, which runs after EWWW’s priority-15 hook. By the time WP Media Cloud offloads the file, EWWW has already finished compressing it. The file in your cloud storage bucket is the compressed version from the first offload. No re-offload is needed.
Background mode
In background mode, EWWW queues compression as a background job and returns without compressing during the upload request. WP Media Cloud detects that EWWW background mode is active and deliberately skips the immediate offload on upload. Instead, WP Media Cloud hooks into EWWW’s ewww_image_optimizer_after_optimize_attachment action, which fires when the background compression job completes. At that point WP Media Cloud offloads the already-compressed file to cloud storage. This ensures only the optimized version is ever sent to the bucket — the uncompressed file is never offloaded.
This is different from other image optimizers where WP Media Cloud offloads immediately and then re-offloads once compression completes. With EWWW background mode, WP Media Cloud waits and offloads once.
Configuration#
No configuration is required. WP Media Cloud detects EWWW Image Optimizer automatically and reports its status, background mode state, and cloud API key status on the Integrations tab in the plugin dashboard.
EWWW works in two compression modes:
- Local (server-side) mode — compression runs on your server using server-side tools. No EWWW API key required. Free for unlimited images.
- Cloud API mode — compression is sent to EWWW’s cloud API. Requires an EWWW API key. Produces better compression results, especially for lossless formats.
Both modes work with WP Media Cloud. The compression mode setting is in EWWW Image Optimizer’s own settings panel and does not affect WP Media Cloud’s behavior.
EWWW Easy IO CDN#
EWWW Image Optimizer includes an optional CDN feature called Easy IO (ExactDN). This is a separate configuration from image compression and is covered in the EWWW Easy IO CDN documentation. You can use EWWW for compression without enabling Easy IO CDN, and you can use Easy IO CDN without using EWWW’s compression features.
Bulk optimization after migration#
If you run the WP Media Cloud bulk migration tool to offload your existing media library and then want to compress those files with EWWW, run EWWW’s bulk optimization tool after the migration completes. In synchronous mode, EWWW will compress each file and WP Media Cloud will re-offload the compressed version. In background mode, EWWW queues each file and WP Media Cloud waits for the background job before offloading.
Troubleshooting#
Files are not being offloaded after upload in background mode
In background mode, WP Media Cloud deliberately waits for EWWW’s background job to complete before offloading. If files are not appearing in cloud storage, check whether EWWW’s background queue is processing correctly. Go to EWWW Image Optimizer > Bulk Optimize and confirm the queue is running. If background processing is stalled, WP-Cron or loopback requests may be blocked — check the Health tab in WP Media Cloud.
Offload happens before compression completes
This should not happen with EWWW in background mode — WP Media Cloud detects background mode and skips the immediate offload. If you see uncompressed files in your bucket, confirm EWWW’s background mode setting is actually enabled in EWWW settings. If background mode is disabled, EWWW runs synchronously and WP Media Cloud’s normal upload flow applies.
EWWW is not compressing files after offloading
In synchronous mode EWWW runs before offloading, so this would indicate EWWW is not processing on upload at all. Check EWWW’s settings to confirm it is configured to optimize on upload. In background mode, check the queue status.