About CompressJPEG
A straightforward, no-nonsense tool for reducing JPEG file sizes — built to be fast, private, and free for everyone.
Why we built this
Large image files are one of the most common and avoidable causes of slow websites. A single unoptimized photo can weigh more than an entire page's worth of HTML, CSS, and JavaScript combined. Yet most people have no easy way to fix that without installing software or paying for a subscription.
We wanted something simpler: open a page, drop your images, get smaller files. No account, no watermark, no limit on how many times you use it.
CompressJPEG was built for developers, designers, bloggers, and anyone who regularly works with images and just needs them to be smaller — without spending time on it.
How the compression works
Under the hood, it's a combination of well-established image processing techniques — nothing magic, just applied carefully.
1 JPEG quality factor
JPEG compression works by adjusting a quality factor between 1 and 100. Lower values discard more frequency information from the image's internal DCT (Discrete Cosine Transform) representation, producing smaller files at the cost of some visual sharpness. Most images look identical to the human eye at quality 70–85, even though the file can be 60–80% smaller than the quality-100 original.
2 Binary search for target sizes
When you choose a target file size (say, 100 KB), the tool doesn't guess — it runs a binary search. It tries a mid-point quality, checks the resulting file size, then narrows the range up or down. After 6 to 8 iterations it converges on the highest quality that still fits within your limit. This is accurate to within 5% of the target.
3 Progressive JPEG encoding
All output files are saved as progressive JPEGs. Unlike baseline JPEGs (which load top to bottom), progressive JPEGs display a low-resolution version of the entire image immediately, then sharpen it as more data arrives. This makes pages feel faster even before the image has fully downloaded — a technique used by most major image-heavy websites.
4 EXIF orientation correction
Smartphone photos often include an EXIF orientation tag that tells the viewer how to rotate the image, rather than storing it rotated in the pixel data. Some tools ignore this, producing sideways thumbnails. Our compressor reads the EXIF tag and physically rotates the image data before saving, so the output always appears correctly oriented regardless of where it's viewed.
Privacy by design
We don't want your images any longer than it takes to compress them. Every file you upload is stored in a temporary, session-scoped folder on the server. A background cleanup process deletes all files in that folder after one hour — regardless of whether you downloaded them or not.
No images are shared, analysed, used for training, or retained. We don't log filenames or track what you upload. Once the session expires and the cleanup runs, there is no record that the files ever existed on our server.
For the full details on how data is handled, read our Privacy Policy.
Ready to compress your images?
No account needed. Just drop your JPEG files and get smaller images in seconds.
⚡ Start Compressing