How to Compress an Image to 100 KB

Start from the destination requirements

Confirm whether the form accepts JPG, PNG, or WebP and whether it imposes minimum dimensions. A tiny file that falls below the required pixel size is still unusable.

Target a modest margin below 100 KB because file-property displays and upload validators can round differently.

• Record minimum and maximum dimensions.
• Choose only an accepted format.
• Preserve readable text and recognizable faces.

Search quality instead of guessing

For JPG and lossy WebP, a bounded binary search can test candidate qualities and retain the highest tested result at or below the limit. File size does not always change monotonically at every tiny step, so the final result still needs direct verification.

PNG does not expose a universal browser quality control. When exact PNG output is required, dimension or color-detail changes may be necessary.

Reduce dimensions in controlled steps

When even a low-quality full-size image exceeds the limit, lower width and height together. Each step reduces pixel count, after which the quality search can restart.

This can preserve cleaner local detail than forcing a huge image through an extremely low quality setting. It still cannot make an arbitrarily detailed image fit with no visible loss.

• Lock aspect ratio.
• Prefer several bounded steps over a blind collapse.
• Compare facial detail, small text, and high-contrast edges.

Interpret success and failure truthfully

A successful target result is at or below 100 KB based on its generated Blob size. An unsuccessful attempt should show the smallest candidate found and state that it remains above target.

Do not rename or round an above-target result to imply success. If the remaining quality is unacceptable, the correct answer may be that the target and content requirements conflict.

• Verify bytes after export.
• Keep a safety margin below the ceiling.
• Retain the master and document any required compromises.