Question 1

Does compressing an image reduce its dimensions?

Accepted Answer

No — compression here only affects file size and quality through re-encoding, not pixel dimensions. Use the Image Resizer if you also want to change the width or height.

Question 2

What's the difference between JPEG and WebP output?

Accepted Answer

WebP generally achieves smaller file sizes than JPEG at the same visual quality, though JPEG has broader compatibility with older software and platforms.

Question 3

Will compressing a PNG reduce its size the same way?

Accepted Answer

Not with this tool's quality slider — PNG is lossless and has no quality setting. To meaningfully shrink a PNG, convert it to JPEG or WebP here instead.

Question 4

Is my image uploaded to a server?

Accepted Answer

No — everything happens locally in your browser using the Canvas API; your image never leaves your device.

Question 5

What happens to transparency if I compress to JPEG?

Accepted Answer

JPEG doesn't support transparency, so any transparent areas are filled with white before compressing — not left black, which is what plain canvas re-encoding does if you don't handle it. If you need to keep transparency, choose WebP instead.

Question 6

Why does it say the file got bigger instead of smaller?

Accepted Answer

It can happen if the original was already well-compressed, or the quality you picked is close to lossless — re-encoding adds a small amount of overhead that isn't always offset by the savings. Try a lower quality or WebP, which usually compresses better than JPEG at an equivalent quality.

Image Compressor

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Supported formats & limits

Example

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Frequently asked questions

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