How Image Resizer Works

File validation and decoding

When you choose a file, the browser checks its type and size, decodes the image, and reads the pixel dimensions. A file extension alone is not treated as proof that the image can be processed.

Dimension and fit calculation

The requested resize mode determines the output dimensions. When the source and destination ratios differ, the selected fit method decides whether the image is padded, cropped, or reshaped.

JPEG and WebP target search

For JPEG and WebP target-size compression, the encoder is tested at different quality values. The tool keeps the highest result it can find below the selected limit rather than claiming an exact byte match.

• Keep the original file before editing.
• Check dimensions, crop, transparency, and file size after download.
• Do not send private source images when reporting a problem.

Optional resolution reduction

When quality reduction is not enough and automatic dimension reduction is enabled, width and height are lowered in controlled steps. The final dimensions are shown before download.

Download and memory cleanup

Processed files are held in temporary browser memory. Object URLs, temporary canvases, and worker resources are released when they are no longer needed or when the editor is cleared.

What you should verify

Open at least one downloaded file and confirm its dimensions, bytes, crop, transparency, color, and readability. Keep the source because re-encoding can remove metadata and cannot restore discarded pixels.