Compress Image
Make an image file smaller by re-encoding it and, if you choose, capping its dimensions — with true before/after sizes.
Email limits and upload caps hate big photos. Re-encode a JPG at a quality you control and optionally shrink its dimensions, then see the exact sizes before and after. PNG files stay lossless, and everything happens in your browser.
Your image never leaves your browser — compression happens on your device.
How to use this calculator
- Choose the image to compress.
- Set the quality slider (80% is a good start) and a max dimension if the image is oversized.
- Click Compress Image.
- Compare the before/after cards and keep the downloaded file.
The formula
If the longest side exceeds the cap, scale = cap ÷ longest side and both dimensions are multiplied by it. A 4000 x 3000 photo with a 1920 cap scales by 0.48.
Worked example
A 4000 x 3000 px photo capped at 1920 px becomes 1920 x 1440 px — the same proportions at 48% of the width and height, before quality savings are even counted.
Frequently Asked Questions
What quality setting should I pick?
80% is the sweet spot for photos: typically 60-80% smaller files with no visible difference at normal viewing sizes. Drop to 60-70% for thumbnails and previews; stay at 90%+ when the image will be printed or edited further.
Why did my PNG not get much smaller?
PNG is lossless, so re-encoding it at the same dimensions saves almost nothing. PNG savings here come only from resizing. For photographs, converting to JPG with the Convert Image Format tool usually cuts the file to a tenth of the PNG size.
Does compressing change the dimensions?
Only if you set a max dimension smaller than the image. The longest side is scaled to that cap and the other side follows the aspect ratio, so nothing is stretched. Choose 'No resize' to keep the exact pixels and save purely through re-encoding.
Is my photo uploaded anywhere?
No. The image is decoded and re-encoded by your browser's own canvas engine on your device. Nothing is transmitted or stored.
Why does the result say 'No smaller'?
Some images are already efficiently encoded — a heavily optimized JPG at your chosen quality can occasionally re-encode to the same or a slightly larger file. Lower the quality slider or cap the dimensions and run it again.