How to Compress an Image to 20 KB Free (Signature & Photo)

To get an image under 20 KB, you have to cut its pixels hard before you touch the quality. Crop tightly, resize to about 250-300 pixels wide, then save it as a JPG at 60-75% quality. A signature at that size usually comes out between 5 and 15 KB, and a small face photo between 12 and 20 KB. All three steps are free in your browser, ending with the free image compressor, and nothing is uploaded.

It shows up on exam and recruitment forms for the signature (often with a minimum of 10 KB as well), on older portals for the photo, and on sites that want a tiny thumbnail or avatar. For comparison, a single phone photo is usually 2-5 MB, which is 100 to 250 times too big.

Why 20 KB needs a different approach

With a 100 KB or 200 KB limit, you can often get there by lowering the quality slider a bit. At 20 KB you can't. Quality only decides how much detail each pixel keeps; it can't make a 4000-pixel-wide image small. Even at the lowest setting, a full-size phone photo stays far over 20 KB and looks like a mosaic.

File size roughly follows the number of pixels: halve the width and you have a quarter of the bytes. That's why the order matters:

1. Crop away everything the form doesn't need.
2. Resize to a small width.
3. Compress with a moderate quality drop.

Step 1: Crop tightly

Open the free image cropper and drop in your photo or the picture of your signature.

• For a signature, choose Free as the shape and drag the box so it hugs the ink with a thin white margin. A signature photographed on a full sheet of paper is mostly blank page, and the paper costs bytes too: shadows, texture and slight colour changes all need storing.
• For a face photo, choose Passport 35×45 mm and frame your head and shoulders. The box keeps that shape while you drag it.

Save the crop as JPG, then click Crop image and download it.

Step 2: Resize small

Now open the free image resizer, choose Pixels, keep Lock proportions on and type a width. Good starting points for a 20 KB limit:

What you're uploading	Width to try	Typical size after Step 3
Signature (wide strip)	250-350 px	5-15 KB
Face photo	200-260 px	10-20 KB
Thumbnail or avatar	150-200 px	5-12 KB

If the form gives exact pixels, such as 140 × 60 for a signature, type those instead. You may need to switch Lock proportions off to hit both numbers; if the result looks squashed, go back and crop closer to that shape first.

Keep Save as on JPG and click Resize image. The resizer saves at high quality, so the file will still be a bit bigger than you want. That's fine: the next step trims it.

Step 3: Compress and read the size

Open the free image compressor:

1. Drop in the resized image.
2. Under Save as, pick JPG.
3. Move the Quality slider to 70% and click Compress image.
4. Read the result line: it shows the old size, an arrow and the new size, with the percentage saved.
5. Over 20 KB? Try 60%, then 50%. Still over? Go back to Step 2 and take 50 px off the width.

Under about 50% you'll see blocky smudges around letters and hair. At that point a narrower image is the better fix, every time.

When the form also sets a minimum

Many forms ask for something like "10 KB to 20 KB". A neat signature can easily come out at 6 KB, which gets rejected for being too small. Raising the quality slider won't fix that: the compressor never hands back a file bigger than the one you dropped in (it shows "kept as is" instead), so an already-small file can't be pushed up. To get a bigger file:

• Go back to the resizer and resize the cropped original a little wider, say 350-400 px instead of 280 px. The resizer saves at about 92% quality, so check its size first; it may already be in range.
• If it's now over 20 KB, compress that wider copy at 70-80%.

Aim for the middle of the range, around 14-16 KB, so a tiny change on the form's side doesn't tip you over either edge.

Getting a clean signature photo in the first place

A clean source image compresses far better than a messy one. Before you start:

Sign in black ink on plain white paper, photograph it straight on in daylight with no shadow across the page, and fill most of the frame with the signature. Grey paper, shadows and crumpled pages add "noise" that JPG has to store. There's a full walkthrough in how to resize a signature for online forms.

Should you use WebP or PNG instead?

Stick with JPG unless the form says otherwise. WebP is often smaller, but many portals only accept JPG or JPEG, and PNG makes photos and phone-snapped signatures much larger. Upload whatever format the form lists.

Related limits

If your limit is a little more generous, these guides use different settings:

• Compress an image to 50 KB: the usual passport-photo limit.
• Compress an image to 100 KB: photos with more detail and profile pictures.
• Compress an image to 200 KB: ID cards, certificates and document pages.

And for the full set of rules forms tend to give, see reducing photo size for exam forms. Each exam or service sets its own size, pixel and format rules, so always check its official notice.

Do it now

Crop, resize to about 250-300 px wide, then finish in the free image compressor at 60-75% quality. Your signature and photo stay on your device the whole time, and you don't need an account.