Troubleshooting

Most compression problems are not bugs. They are one of about six things, and they are all fixable. Work down this list.

My image barely got smaller

Almost always one of three causes.

It was already compressed. Lossy compression discards detail. An image that has been through a compressor once has already lost the detail that was cheap to lose, and a second pass has very little left to take. If your source is a JPEG you downloaded from somewhere, you are compressing a compressed file. Go back to the original if you have it.

It is a photograph saved as a PNG. PNG is lossless and stores every pixel exactly. It was designed for graphics, not photographs, and no PNG optimizer will fix that. Change the output format to WebP or JPEG and the file will typically drop by 80 percent or more.

It is already small. An image under about 50 KB has little redundancy left to exploit. Saving 5 percent of 30 KB is not worth thinking about.

My PNG is still enormous

See above: it is probably a photograph. PNG compression here is lossless, which means the output has exactly the same pixels as the input. That is a guarantee, and it is also a ceiling on how much smaller the file can get.

If the image genuinely is a graphic, a logo, or a screenshot, and it is still large, it is likely stored as full 24-bit color when it only contains a few hundred distinct colors. It will still compress, but converting to WebP will almost always beat it.

The compressed file came out larger than the original

This happens, and the tool will tell you so with a positive percentage instead of a negative one. Two common reasons.

Converting a small, flat graphic to a lossy format can add bytes, because lossy encoders spend bits describing the noise they introduce around hard edges. Keep graphics in PNG or lossless WebP.

Converting an already-optimized JPEG to PNG will always make it much larger, because you are going from a lossy format to a lossless one. The PNG has to store every JPEG artifact exactly.

AVIF is taking a long time

That is expected. AVIF uses the AV1 codec, which searches much harder for redundancy than a JPEG or WebP encoder does. That search is exactly what produces the smaller file. On a large image it can take several times as long as a WebP encode.

It is a one-time cost, paid by you when you build the page, and not by your visitors when they load it.

My transparent background turned white or black

You converted to JPEG. JPEG has no alpha channel and cannot store transparency, so transparent pixels have to become some solid color. This is a property of the format, not a setting.

Keep the output as PNG, or convert to WebP or AVIF. Both of those support transparency.

The image looks blurry or blocky

Your quality setting is too low for that image. Different images tolerate different quality levels: a photograph of foliage hides artifacts well, while a smooth gradient or a flat brand color shows them immediately.

Move the slider back up. Quality 80 is a safe default. Below about 60 you will start to see blocking in flat areas like skies and skin. Re-compressing the same image at a different quality is free within a session, so try a few values and compare.

The colors changed

Two possibilities. If the shift is slight, we stripped an embedded color profile along with the rest of the metadata, and your image was in a wide gamut space that the browser is now interpreting as sRGB. Export your original as sRGB before compressing.

If the shift is dramatic, the image was probably CMYK. CMYK is for print. Convert it to RGB first.

"This is not a supported image"

The file could not be decoded. Usually it is not the format you think it is: a .jpg extension on a HEIC file from an iPhone, a .png that is really a TIFF, or a partially downloaded file. Open it in an image viewer to confirm it is intact, then re-export it.

If the upload fails this way, no unit is charged. The reservation is refunded.

"File is over the per-image limit"

The free tier accepts images up to 25 MB. Paid plans go to 50 MB on Pro, 100 MB on Agency, and 200 MB on Business. If you are hitting this with a photograph, it is almost certainly larger in dimensions than it needs to be. Resize it first.

"Monthly limit reached"

You have used your plan's allowance for the calendar month. It resets on the first of the next month, UTC. Upgrading takes effect immediately and the new allowance applies at once.

Remember that a unit is one uploaded image per session. If you think the number is wrong, note that re-compressing an image you already uploaded, at any quality or in any format, does not consume another unit. Only a new image does.

The API returns 410 Gone

The result was deleted under the retention policy. Files uploaded through the API and their results live for 24 hours; images compressed with the browser tool live for one hour. A scheduled job removes anything past its window.

Download promptly, or submit the job again. There is no way to recover a deleted file, which is the point of deleting it.

The download link stopped working

Signed URLs expire after 15 minutes. Request the download endpoint again and you will get a fresh one, provided the file is still inside its retention window.

Still stuck

Email the address in the footer with the job id if you have one. Do not send the image itself in a first email.