Updated · 2026-08-05
How to compress an image under 100 KB
Search engines and forms often cap uploads at a fixed size — 100 KB is a common one for avatars, forum posts, and government or academic portals. Getting there without visibly wrecking the photo means controlling exactly how much Shrink compresses, not just applying a fixed quality slider and hoping.
Open Shrink and pick a target size
Drop your PNG or JPG into Shrink, then switch from Keep Format to a target file size — 100 KB, 500 KB, 1 MB, or a custom value you type in. Target file size is a Pro feature, since it runs a more thorough search than the free Keep Format mode.
Let the quality search do the work
Once a target is set, Shrink searches downward through encode quality until it finds the highest quality whose output still fits your budget. It's the same SSIM-guided search Shrink always runs, pointed at a byte count instead of a fixed quality, so you get the best-looking result available inside that size rather than the first pass that happens to fit.
When 100 KB asks too much
A large photo full of fine detail may not survive a 100 KB budget without visible softening — file size and pixel dimensions both push against quality. If Shrink can't reach your target, it returns the smallest result it could produce rather than degrading further, so you always get something back. Resizing to smaller pixel dimensions first, then compressing, gets you further under a tight budget than compression alone.
Keep Format vs. Smallest
Target file size works alongside Shrink's Keep Format and Smallest modes. Keep Format holds your PNG as a PNG or your JPG as a JPG while hunting for the target; Smallest (also Pro) additionally considers WebP and AVIF output, which compress more efficiently and make a small target easier to hit without sacrificing as much visible quality.
Questions
Is compressing to an exact file size free?
No — target file size (100 KB, 500 KB, 1 MB, or custom) is a Pro feature. Guests and free accounts use Keep Format mode, which compresses as far as it can while keeping the image visually unchanged, without targeting an exact byte count.
Will my image definitely end up under 100 KB?
Shrink searches hard for a fit, but very large or detailed source images sometimes can't reach a tight target without visible quality loss. In that case it returns its best-effort result rather than compressing past the point of usefulness.
Does target file size ever make my file bigger?
No. Across every mode, Shrink checks its result against your original and never returns a file larger than what you uploaded — if a target can't help, you get the original back unchanged.
What's the fastest way to hit a very small target, like 50 KB?
Resize the image down first — fewer pixels need far less data to represent at the same visual quality — then run Shrink's target-size mode on the smaller result.