Reduce Image Size in KB

100KB is the single most common image size limit on the internet. It appears in upload forms, content guidelines, performance budgets, and platform specifications more often than any other round number, which makes it the default target most people are looking for.

The budget is generous enough for real quality. A photograph at 1200×800 to 1600×1000 pixels typically fits at a quality level where compression is not visible in normal use, and graphics or screenshots can go considerably larger because flat colour costs very little to encode.

This page is for the common case where a limit is expressed in KB rather than in pixels, and you need to hit that number precisely.

A kilobyte is a measure of data, not of picture quality or dimensions, and the relationship between them is not fixed. Two images with identical pixel dimensions can differ tenfold in kilobytes depending on how much detail they contain and which format they are stored in. A photograph of a busy market is expensive to encode; a photograph of a clear sky at the same resolution is cheap.

This is why file size targets behave unpredictably if you think only in terms of dimensions. Three levers actually control the number: the pixel dimensions, the compression quality, and the format. Changing format alone — from PNG or JPG to WebP — often achieves a large reduction before either of the other two levers is touched, which is why every download from this tool is WebP.

There is also a units wrinkle worth knowing. Operating systems and upload forms do not always agree on whether a kilobyte means 1,000 bytes or 1,024. A file your computer reports as 100KB can be measured as 102KB by a stricter server, which is why leaving a small margin below any hard limit is worth the negligible quality cost.

This page accepts JPG, JPEG, PNG, and WebP inputs, which covers essentially every image you are likely to encounter outside of specialist workflows. Each behaves a little differently under compression, and the tool adapts to what you give it.

Output is always WebP. That choice is deliberate: WebP reaches a given target size at higher visual quality than JPG or PNG can, which means the file you download looks better than the equivalent-sized file in an older format would.

Upload JPG, JPEG, PNG, or WebP images. Downloads are optimized WebP files.

Balanced mode with resize at around 1600px wide is the general-purpose answer. For images that will be displayed small, drop the resize width and you will land far below 100KB with excellent quality — there is no benefit to using the whole budget if you do not need it.

Use Balanced mode first. If the output is still too large, enable resize with a 1200px or 800px max width.