smaller files, same workflow
Compress JPG, PNG and WebP online
Oversized photos slow down websites, bounce email attachments, and blow past upload limits. OneImageTool compresses images in your browser — tune quality with a slider, compare before and after, and download when you are happy.
For the biggest savings on PNG sources, switch output to WebP or JPG. Use the quality slider and format options to balance size and clarity.
output formats
What you can export
Pick the format that fits your workflow. JPG and WebP respond strongly to the quality slider; PNG keeps lossless transparency but may not shrink as much unless you convert to WebP.
| Format | Best for | Notes |
|---|---|---|
| JPG | Photos, general web images | Smallest files for photos; no transparency |
| WebP | Modern web, apps, CMS uploads | Great size/quality balance; transparency supported |
| PNG | Graphics with sharp edges or alpha | Lossless; use WebP if you need a smaller file |
three steps
How to compress an image online
Upload
Drop a JPG, PNG, or WebP. Original dimensions and file size appear instantly.
Adjust
Move the quality slider and drag the compare handle to check detail. Switch output format if you need WebP or JPG.
Download
Save the compressed file when the preview and file size look right.
where smaller files pay off
When to compress an image
Faster web pages
Images are usually the heaviest assets on a page. Compressing a 3 MB hero photo down to 300 KB cuts load time on slow connections and improves Core Web Vitals like Largest Contentful Paint — without swapping the image or changing your layout.
Email and form limits
Attachment limits of 10–25 MB and upload forms that cap files at 2 MB are everywhere. A quality setting of 75–85 usually gets a photo under the limit while staying visually identical at normal viewing sizes.
Social and marketplace posts
Platforms re-compress whatever you upload. Sending a reasonably sized file gives their encoder less to destroy, so your listing photo or post often ends up looking better than if you had uploaded the raw camera file.
Storage and backups
Screenshots and camera exports pile up. Re-encoding an archive folder as WebP at quality 80 routinely halves its size with no visible difference on screen.
know the limits
When compression will not help much
If a file was already compressed — a JPG saved from a photo editor at quality 70, or a WebP downloaded from the web — re-compressing it saves little and can stack visible artifacts on top of the ones already baked in. When savings look small in the stats panel, that is usually why.
Screenshots, text-heavy graphics and line art suffer at low JPG quality: sharp edges pick up ringing and smudge. For that kind of content, keep PNG, or use WebP at a high quality setting instead of pushing the JPG slider down.
The biggest single win is usually a photo saved as PNG. PNG is lossless, so photographic content stores far more data than it needs — switching the output format to WebP or JPG often cuts the file by 60–90% before you touch the quality slider. Very small files (under roughly 50 KB) are rarely worth optimizing further.
pick the right tool
Compress vs resize vs convert
Compressing re-encodes the same pixels with fewer bytes — width and height stay unchanged. If the image is genuinely larger than you need (a 4000px camera photo destined for an 800px slot), resize the image first; fewer pixels shrink the file more than any quality slider can.
Changing format is compression by another name. A photo stored as PNG shrinks dramatically when converted to WebP, transparency included — often a bigger saving than lowering JPG quality.
Processing a whole folder? The batch compressor handles up to five images at once and bundles them into a ZIP. And if you are preparing tiles for a social grid, split the image first, then compress the exported tiles so each one uploads quickly.