Quick answer
When Batch compression fails, troubleshoot in order: file/format, permission/lock, output settings, another tool. Set one target (size/quality/format), spot-check a few, then run the batch.
Why it matters
Start with the most common and cheapest causes to narrow it down fast.
Do not use one quality for both text and photos.
Step by step
- Back up the original; never overwrite the only copy.
- Confirm the target platform's format, dimensions and size limit.
- Cap the longest side first, then quality; change one variable at a time.
- Compare size and sharpness after compressing, and step back one setting if needed.
- Keep the original until the output is confirmed.
Common mistakes
- Chasing the smallest file and blurring text/edges.
- Converting transparent PNG to JPEG, turning transparency white or black.
- Recompressing the same file and accumulating loss.
- Overwriting the original, so a bad result cannot be undone.
Checklist
- Original backed up.
- Output format/dimensions/size meet the platform.
- Text is readable and transparency is correct.
- Verified in the real page/email/upload field.
- Original kept until confirmed.
Key facts
- Do not use one quality for both text and photos.
- Spot-check 2-3 outputs after a batch to catch global mistakes.
FAQ
How do I troubleshoot a failed Batch compression task?
When Batch compression fails, troubleshoot in order: file/format, permission/lock, output settings, another tool. Set one target (size/quality/format), spot-check a few, then run the batch.
How long does it take?
Usually 1-3 minutes; for intermittent issues, run 30 seconds and retest elsewhere.
Is data uploaded?
Runs locally and does not upload video/audio; extensions may still read the page.
Source: ImageMagick