Image Compressor

Re-encode a browser-supported image and compare its output size. JPEG quality is adjustable; PNG keeps transparency.

How to Use

Choose an image

Select a file no larger than 20 MB that your browser can decode.

Adjust JPEG quality

For non-PNG input, compare the preview at different quality levels. PNG quality is fixed by the browser encoder.

Inspect size and appearance

Check readability, transparency, and whether the generated output is actually smaller.

Download and reopen

Keep the original image and check the exported file in its destination application.

Choose settings that match the output

The tool draws the decoded image to a canvas at its original pixel dimensions. PNG input produces PNG output; other supported images produce JPEG output. The quality slider applies to JPEG only. PNG transparency is retained; JPEG output uses a white background.

Check the result

Start with the default 80% quality for JPEG, inspect the preview, then lower quality if needed. Compare actual generated bytes and reopen the downloaded file. Re-encoding can increase file size, so a saving is not guaranteed.

How It Works

Output size is calculated from decoded Base64 bytes, excluding the data URL header and padding. Saving (%) = (input bytes − output bytes) / input bytes × 100 A 200,000-byte input and 150,000-byte output save 25%. A larger output is reported as larger, not as a successful reduction.

Frequently Asked Questions

Why does the PNG quality slider not work?▼

Canvas PNG export does not use the quality argument. The slider is disabled for PNG. Reduce pixel dimensions with the Image Resizer if appropriate.

Why is my result larger?▼

The source may already be well compressed. A different encoder or output format can produce more bytes; no reduction is guaranteed.

Are animation and metadata preserved?▼

No guarantee is made. Canvas exports a new still image and can discard animation, metadata, and color-profile information.

Can a file below 20 MB still fail?▼

Yes. Decoded pixel dimensions can exceed the browser’s canvas or memory limits even when the compressed file is small.

Limits and assumptions

20 MB input-file limit; decoding also depends on browser codec and memory support.
PNG quality is not adjustable. Non-PNG input is exported as JPEG.
Animation and original metadata are not preserved; smaller output is not guaranteed.

Worked guides

Choose image compression settings and verify the download

References

MDN: Canvas export behavior

Documentation updated on 2026-10-04. How we review tools

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