How to get an image under 100 KB

Set a 100 KB limit

100 KB isn’t one of the tool’s preset limits, so you set it under Custom: type 100 and choose KB. The button on this page does that for you. The tool opens with 100 KB already chosen.

Check the form says KB and not MB. 100 KB is a tenth of 1 MB. If the numbers are close and the form still refuses your file, see KB and MB.

What happened at 100 KB in our tests

We tested two JPG photos in two browser engines, Chromium and WebKit, on a computer: a 12-megapixel photo we generated for testing (4000 × 3000 pixels, 3,422,855 bytes), and a real street photo (3840 × 2880 pixels, 1,446,573 bytes).

With the default settings, both fitted, at 65% quality:

• The 12-megapixel photo came out between 1270 × 952 and 1677 × 1258 pixels, from 4000 × 3000.
• The street photo came out between 1066 × 799 and 1163 × 872 pixels, from 3840 × 2880.

With “Keep original dimensions” turned on, neither fitted. At the lowest quality the tool uses, 45%, the smallest copies were 446,401 bytes and 535,915 bytes, more than four times the limit. The tool showed them as “Closest we could get”, not as fits.

Note: That is what happened with these two photos. Other images can come out differently, larger or smaller in pixels.

Why the pixel size can differ between browsers

The same 12-megapixel photo came out 1677 pixels wide in Chromium and 1270 pixels wide in WebKit. Each browser engine resizes the picture in its own way, so the copies it makes compress differently, and the tool finds a different largest size that fits.

Each copy was checked and was under 100 KB. The result screen shows the width and height of the copy you got.

What to check in the copy

• Fine text. Small writing in a photo, or the text of a scanned document, needs enough pixels to stay readable. Open the copy and read it. Compare closely on the result screen shows the original and the copy at the same spot, up to 200%.
• A minimum pixel size. Some forms ask for a width and height as well as a file size. The result screen shows the copy’s width and height, so check them against the form.
• Faces and important details. Make sure anything the reader of the form needs to see is still clear.

For screenshots and pictures of text, MDN notes that blurring and coloured fringes around text and sharp edges are very visible with lossy formats, such as JPG.

If it won’t fit

• “Keep original dimensions” is on. At 100 KB it couldn’t reach the limit for either test photo. Choose the “Allow resizing, keep JPG” change (the card names your file’s type).
• It’s a PNG. The tool has no quality setting for PNG, so a PNG only gets smaller in pixels. If the form accepts JPG, choose Convert to JPG. A transparent background becomes white, and the tool only does that when you choose it.
• WebP. If the form takes WebP, Convert to WebP is offered only when your browser can save WebP files.
• It reached the smallest size. The tool never goes below 640 px on the longest side. If it can’t fit even there, it says so and shows the closest size it got.

If your image has to be smaller still, see how to get an image under 50 KB. For choosing a file type, see JPG, PNG or WebP.