Compress & convert images

When compression is worth doing

A photo straight off a modern phone is typically 3 to 6 MB and around 4,000 pixels wide. Almost nowhere you will send it actually needs that. A website hero image is usually shown at 1,600 pixels or less, an email attachment gets scaled down by the mail client, and a WhatsApp or Slack upload is recompressed on the way through. Compressing first means faster uploads, quicker page loads and less storage, and in most cases nobody can tell the difference.

The tool above does two things at once. It can re-encode an image into a more efficient format, and it can lower the quality setting of a lossy format so the encoder throws away detail your eye does not notice. You can combine either of those with a maximum width to downscale images that are simply larger than they need to be.

Choosing a quality setting

The quality slider maps to the encoder's quality parameter, and it is not linear. The difference between 100 and 90 is usually a large file-size drop with no visible change, while the difference between 60 and 50 starts to introduce blocking and smearing in flat areas like skies and skin. As a rule of thumb:

Screenshots, diagrams and anything with sharp text behave differently from photos. Lossy compression blurs hard edges, so for those it is better to keep PNG (lossless) and let the built-in PNG optimisation reduce the size instead.

Which output format to pick

• WebP is the best general choice for the web today. It is about 25 to 35% smaller than a JPG of the same visual quality, supports transparency, and is supported by every current browser.
• AVIF compresses harder still, often 50% smaller than JPG, but encoding is slow in the browser and a few older devices and image viewers cannot open it. Use it when file size matters most and you control where the image is displayed.
• JPG remains the safe choice for anything that will be opened outside a browser: email attachments, printing services, older software and CMS platforms with strict upload rules.
• PNG is lossless. Use it for screenshots, logos, line art and anything with transparency that needs crisp edges.

Batch tips

Drop an entire folder's worth of images at once. Every image gets the same format, quality and maximum-width rules, and the results can be downloaded as a single ZIP. Because encoding happens on your device, a batch of a hundred phone photos takes a minute or two on a laptop and somewhat longer on a phone. Keep the tab in the foreground while it runs; browsers throttle background tabs.

If you only want to shrink dimensions and not touch quality, set the max width and leave quality at 95. If you only want a format change, leave the width at 0. The converter never upscales, so a small image stays small.