How to Compress an Image to 100 KB, 50 KB or Any File Size

A phone photo is usually 2 to 5 MB. Then an exam registration, job portal or visa form asks for a picture "under 100 KB", or a signature "between 10 and 20 KB", and the upload keeps failing. Getting a file that small is easy. Getting it that small while it still looks sharp takes knowing which of two dials to turn first.

What makes an image file big

File size comes from two things:

• Dimensions, the number of pixels. A 12-megapixel phone photo is about 4000 × 3000 pixels. Halve the width and height and you have a quarter of the pixels, so roughly a quarter of the file size.
• Compression, how much detail the format throws away to store those pixels. For JPG and WebP that's the quality setting. At 80% most people can't tell the difference from the original, yet the file is often a fraction of the size.

Most upload forms show your photo at a few hundred pixels wide. A 4000-pixel photo has far more detail than they will ever use, so there's usually plenty of room to shrink without anyone noticing.

Quality first, then dimensions

The trick is the order. Lowering quality a little costs almost nothing you can see. Lowering it a lot gives blocky patches and smeared edges, which look worse than a slightly smaller picture. So the best result comes from:

1. Trying the highest quality that fits the limit.
2. If even moderate quality (around 50%) is still too big, reducing the dimensions instead of going lower.
3. Picking the largest size that still fits, so you don't lose more detail than you have to.

Our image compressor does exactly this when you type a max file size: it tests quality settings from high to low, and only scales the image down once quality alone can't get it under the limit.

Step by step: compress an image to 100 KB

1. Open the image compressor.
2. Choose JPG as the format, unless the form asks for something else. JPG is what nearly every upload form accepts, and it's efficient for photos.
3. Type the limit into Max file size, or tap a preset like 100 KB. If the form says 100 KB, enter 100 KB, not 99. The tool counts 1 KB as 1,000 bytes, which is the stricter of the two ways sites measure, so the result passes either check.
4. Add your photo. It's compressed on your device in a second or two, and you see the new size and dimensions under the preview.
5. Download it and upload that file to the form. For several photos, use Download all to get them in one ZIP.

The same steps work for 20 KB, 50 KB, 200 KB, 500 KB or 1 MB. Only the number changes.

Which format gives the smallest file?

A common mistake is uploading a photo as PNG. For a photo, PNG can be five to ten times bigger than a JPG that looks the same, so switching to JPG is often all it takes to get under the limit. More on the differences in Transparent PNG explained.

Signatures and very small limits (10 to 50 KB)

Forms often ask for a scanned signature or a thumb impression under 20 KB, and a passport-style photo under 50 KB. Some tips for very small targets:

• Crop first. A signature photographed on a full sheet of paper is mostly empty paper. Crop it tight with your phone's photo editor before compressing, and the limit leaves far more room for the ink.
• Use plain white paper and a dark pen. Clean, high-contrast images compress much better than grey, shadowy ones.
• Check the required dimensions. If the form says something like 200 × 230 pixels, it will probably accept a slightly larger image too, but a huge one rarely fits under 20 KB at good quality. Starting from a cropped photo usually solves this.

When it still won't fit, or looks blurry

• The tool says it couldn't reach the size: the target is very small for that image. Crop away anything the form doesn't need, or switch from PNG to JPG.
• The result looks soft: the image had to be scaled down a lot. A tighter crop keeps more pixels on the part that matters, such as the face or the signature.
• Noise and grain: photos taken in dim light are full of speckles, and every speckle is detail the format has to store. Retake the photo in daylight and it will compress to a much smaller file.
• The form rejects it anyway: check the format (some accept only JPG or JPEG) and the dimensions, not just the size. A file ending in .jpg and .jpeg is the same format.

Do I lose quality every time I compress?

With JPG and WebP, yes, a little each time the image is saved again. So always compress from your original photo, not from a file you already compressed. Keep the original, and if you need a different size for another form, start from the original again.

Is it safe to compress private photos online?

Many online compressors upload your image to their server. Ours doesn't: compression uses your browser's built-in image engine, on your own device, and the photo never leaves it. Re-saving the image also drops hidden EXIF data such as GPS location and camera details, which is a small privacy bonus when you share photos.

Related tasks

• Need a plain white background for an ID photo first? Read how to take a passport photo at home, then compress the result.
• Need several pages in one file under a limit? See scanning documents to a PDF under 1 MB.