How to Compress an Image to 100KB (or 50KB, 20KB)

Plenty of upload forms still set a hard limit: a profile photo under 100 KB, a document scan under 200 KB, a signature under 50 KB. Your phone camera, meanwhile, saves photos at 3–8 MB. Squeezing a file under a limit by guessing quality settings is slow, so this guide shows how to hit an exact size in one go, and what to do when a file simply won’t get small enough.

Everything here works with the free Image Compressor. It runs in your browser, so the photo isn’t uploaded anywhere, which matters when the image is an ID or a personal document.

Quick answer: compress an image to 100 KB

1. Open the Image Compressor and drop in your JPG, PNG or WebP file. You can add several files at once.
2. Under Compress by, choose Target file size.
3. Tap 100 KB, or type any number into Target size (KB). Shortcuts are there for 20 KB, 50 KB, 100 KB, 200 KB, 500 KB and 1 MB.
4. Pick JPG if the site only accepts JPG. Otherwise WebP usually looks better at the same size.
5. Compress, check the before/after comparison and download.

The tool searches for the highest quality that still fits under your target. It only reduces the pixel dimensions if quality alone can’t get there, so you get the sharpest image the limit allows.

What “100 KB” actually means

File size (kilobytes) and image size (pixels) are different things. A 1080 × 1080 photo can be 80 KB or 2 MB depending on how strongly it’s compressed and how much detail it contains. Compression makes a file smaller by discarding detail your eye is unlikely to miss. Resizing makes it smaller by storing fewer pixels.

One detail trips people up: some sites count 1 KB as 1,000 bytes and others as 1,024 bytes. If a form is strict, aim a little below the limit, for example 95 KB for a 100 KB cap, so you pass under either definition.

Realistic targets by image type

Limits vary by site, so always follow the exact number the form asks for. The table is a guide to what’s achievable without the image looking obviously damaged.

When the file still won’t get small enough

Resize before you compress

A 4000-pixel-wide photo has to throw away a lot of detail to reach 50 KB, and the result looks blocky. Shrinking it first gives the compressor far less to store. Use the Resize option in the compressor (for example Max 1080 px wide), or the Image Resizer for smaller or exact sizes such as a 600 × 600 profile photo.

Switch to JPG or WebP

PNG is lossless, so it can’t trade quality for size the way JPG and WebP can. That’s why target-size mode saves PNG files as WebP, keeping any transparency. If the site only accepts JPG, convert with the Image Converter or choose JPG as the output format. Transparent areas become a solid background in JPG.

Crop out what you don’t need

Empty desk around a document, sky above a portrait, white paper around a signature: every pixel costs bytes. A tight crop is often the single biggest saving.

Expect grainy photos to be bigger

Fine noise from low-light phone photos is real detail as far as a compressor is concerned, and it is expensive to keep. Brighter, cleaner photos compress much smaller at the same quality.

Check the result before you upload

Drag the comparison slider across faces and text. Look for blocky edges around letters and smeared skin. If text is hard to read, raise the target a little or reduce the dimensions less. For a deeper look at quality settings, read how to compress images without losing visible quality.

Key takeaways

• Use Target file size mode to hit an exact limit like 100 KB, 50 KB or 20 KB in one step.
• Aim slightly under strict limits, because sites count kilobytes differently.
• Resize and crop first for very small targets; it looks far better than heavy compression alone.
• Use JPG or WebP for small files. PNG can’t shrink by lowering quality.
• Your file is processed on your device, which is the safe choice for IDs and documents.