A compressed image gets bigger when it is re-encoded less efficiently than the original: quality set too high, a photo saved as PNG, an already-optimized file re-encoded, or an image enlarged. For photos, use WebP or JPEG at 75 to 85 percent, keep PNG for flat graphics, and limit the width. If nothing helps, keep the original file.
You drop a photo into a compressor, wait a second, and the "compressed" file is larger than the one you started with. That is not a bug in your browser. It is a consequence of how image formats work. Below are the seven most common causes, from most to least likely, followed by a quick way to diagnose your own file.
1. The original was already highly optimized
A file exported from a professional tool, a good CMS or an earlier compressor has little left to trim. Re-encoding it at a higher quality than it was saved with produces a bigger file with no visible gain. Fix: lower the quality a little, or accept that the file is already efficient. Our compressor returns your original when a same-format re-encode would only make it larger.
2. Quality is set too high
Quality 100% in JPEG or WebP is not "lossless". It is a very expensive lossy setting that can make the file much larger than 85% with almost no visible benefit. Many phones save at a moderate level, so pushing to 100% inflates the file. Fix: use 75 to 85% for photos.
3. You converted a photo to PNG
PNG stores every pixel exactly. For photographs, with their gradients and noise, that is wasteful, and a PNG copy of a JPEG is often several times bigger. There is also nothing to tune: browsers only apply the quality value to lossy formats such as JPEG and WebP, as MDN documents. Fix: keep photos as JPEG, WebP or AVIF. Use PNG for logos, icons and screenshots with flat colors.
4. A screenshot or graphic was converted to JPEG at high quality
The reverse problem. JPEG struggles with sharp edges and text, so to avoid ugly fringes it needs a high quality value, and the file balloons. Fix: save text-heavy graphics as PNG or WebP instead.
5. The image was enlarged
If a small image is scaled up, the file has more pixels to describe even though no new detail exists. Fix: never upscale. In our tool the width setting only shrinks images, it never enlarges them.
6. Heavy grain or noise
Night photos, film grain and high-ISO shots are full of random pixel variation that compression cannot predict. They compress poorly in every format. Fix: reduce the dimensions, or lower quality further than you would for a clean daylight photo.
7. A WebP or AVIF conversion that was not a win
WebP is usually smaller. Google's study measured lossy WebP 25 to 34 percent smaller than JPEG at the same visual quality, and lossless WebP about 26 percent smaller than PNG. Those are averages against standard encoders. Against an already well-tuned JPEG, or with small or palette-based PNGs, the gap can shrink or even reverse. Fix: compare the result with the original and keep whichever is smaller.
Diagnose your file in a minute
| What you see | Likely cause | Try this |
|---|---|---|
| JPEG got slightly bigger | Original already optimized, or quality too high | Lower quality to about 80% or keep the original |
| Photo is many times bigger | Saved as PNG | Switch output to WebP or JPEG |
| Text screenshot is huge as JPEG | JPEG is the wrong format for sharp edges | Use PNG or WebP |
| Small image became bigger | Enlarged, or format overhead | Do not upscale; keep the original format |
| Nothing gets smaller | Noise, or dimensions are the problem | Set a smaller maximum width |
Choose the right format first
| What you have | Best output | Avoid |
|---|---|---|
| Camera or phone photo | WebP or JPEG at 75 to 85% | PNG, quality 100% |
| Logo or icon with transparency | PNG or WebP | JPEG |
| Screenshot with text | PNG or WebP | JPEG at low quality |
| Huge image used on a web page | WebP, with a limited width | Uploading the full camera resolution |
Does removing metadata make a file bigger?
No. Metadata such as camera details and GPS data is usually small, and stripping it only makes the file lighter. When a result is bigger, the cause is nearly always one of the seven above.
Try the fixes in order
- Open the image compressor and add the file.
- Choose WebP, or JPEG if you need maximum compatibility.
- Set quality to about 80%.
- If it is still large, set a maximum width that suits where the image will be used.
Need a specific limit, like 100 KB for a form? See how to compress an image to 100 KB or 200 KB.
Quick answers
Why did my PNG get bigger after compression?
PNG is lossless, so re-encoding it rarely saves much and can add a few bytes. Switch the output to WebP or JPEG for photos, or reduce the width.
Is a 100% quality setting lossless?
No. In JPEG and WebP it is still lossy, just very conservative, and it often produces a file much larger than 85 percent quality with almost no visible difference.
Does converting to WebP always make the file smaller?
Usually for photos, but not always. Small images, already-optimized files and some palette-based PNGs can come out larger as WebP. Compare the result with the original and keep the smaller one.
Can compressing twice make the image worse?
Yes. Each lossy pass discards more detail. Always return to the original file when you adjust settings instead of recompressing the output.
What should I do when a file will not get any smaller?
Lower the maximum width. Reducing pixel count is the strongest way to cut size when quality changes stop helping.
Sources and further reading
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