Auto-optimize
Encode JPEG, WebP, and AVIF at the same quality and keep the smallest.
Runs in this tab. The file stays here.
This runs in your browser. Nothing is uploaded.
About Auto-optimize
Encodes the same image as JPEG, WebP, and AVIF at a quality you set, then downloads the smallest file — all in the browser, with no upload.
People ask for “compress this without ruining it” and then do not want to pick a format. This page picks on size. Same quality number, three encoders, keep the winner. That is a size contest. It is not a perceptual quality search and I will not pretend SSIM ran in the tab.
JPEG has no transparency. If the smallest file is JPEG, the alpha channel is gone. WebP and AVIF can keep it. Read the line that prints all three sizes before you send the result to a designer who needed the hole in the logo.
AVIF is usually smallest and slowest. On a phone it can take a few seconds. That wait is local CPU. If AVIF cannot load, the fallback is WebP, same as the dedicated AVIF page.
How to use Auto-optimize
- 1Drop an image.
- 2Set the quality floor. Lower means smaller and uglier across all three.
- 3Click Compress & download. The printed line names the winner and the sizes it beat.
What it won't do
- Size contest at one quality, not a visual-quality search.
- JPEG as winner flattens transparency.
- Does not resize. A huge photo stays huge, just in a smaller container.
Common questions
Does auto-optimize keep my transparent background?
Only if WebP or AVIF wins. If JPEG is smallest, transparency is flattened. Check the printed format.
Is the smallest file the best looking?
No. It is the smallest at that quality setting. A slightly larger WebP might look cleaner. Use the format shootout if you want to see all four and pick by eye.
Why not include PNG in the contest?
PNG is lossless. It almost never wins a size contest on a photograph, and including it would make the “winner” misleading on graphics. The shootout page lists PNG on purpose.
Is this lossless compression?
No. JPEG, WebP (lossy), and AVIF all discard detail. I will not put “without losing quality” in the title. The quality slider is the trade.
Related tools
Why this one doesn't upload your file
There is no server to upload to. This page is a static file, and the work happens in your browser using the same graphics and WebAssembly code that renders every other site you visit. Your file is read from disk into memory, processed, and handed back as a download. Once the page has loaded you can disconnect from the network entirely and it keeps working. The longer explanation