Quick answer
Before JPEG image, back up the original, confirm format/size/quality requirements and close programs that lock the file. JPEG suits photos and gradients, compresses well but has no transparency; repeated saves accumulate loss.
Why it matters
Poor preparation leads to overwrites, failures and rework.
Quality 80-85% is usually enough for the web.
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
- Quality 80-85% is usually enough for the web.
- Transparent backgrounds need PNG/WebP.
FAQ
How should I prepare before JPEG image?
Before JPEG image, back up the original, confirm format/size/quality requirements and close programs that lock the file. JPEG suits photos and gradients, compresses well but has no transparency; repeated saves accumulate loss.
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: MDN JPEG