How-to
Compress a photo to exactly 100 KB
Some upload forms reject a photo the moment it crosses a hard byte ceiling, usually 100 KB or 200 KB, no matter how good it looks. Dragging a quality slider by eye rarely lands under that number on the first try. The image compressor has a target-size mode built for exactly this: type the KB limit you were given and it searches for the highest quality that still fits under it, entirely in the browser tab.
Step by step
- Open the image compressor and drop your photo in. Switch the mode toggle from "quality" to "target size": instead of a quality slider, you now see a single KB field.
- Type the limit the form asked for, 100 in this case. The tool re-encodes the photo at several quality levels, each time checking the resulting byte count, and narrows in on the highest quality that still lands at or under 100 KB.
- Download the result. The savings summary shows the final size next to the original so you can confirm it is under the limit before you upload it to the portal that asked for it.
Why some forms demand an exact KB ceiling
Visa applications, exam board registrations and government e-forms often store the photo in a fixed-size database field or attach it to a document template with a hard byte budget. The form does not care about resolution or how sharp the photo looks; it checks one number, the file size in kilobytes, and rejects anything over it. A phone photo straight out of the camera is commonly 2 to 6 MB, twenty to sixty times over a 100 KB cap, so "just resize it a bit" rarely gets there.
How the search finds a size instead of a quality
Target-size mode does not pick a quality number for you to eyeball; it runs a small search. Each attempt re-encodes the photo at a candidate quality and measures the output in bytes. When an attempt is under your limit, the tool keeps it as the best answer so far and tries a slightly higher quality; when it is over, it tries lower. After a handful of attempts it settles on the highest quality it found that stays at or under your KB limit, and re-encodes once more at that value for the file you download. The result lands under the target, not at an exact byte count: 97.4 KB for a 100 KB limit is a typical, and perfectly valid, outcome.
When the target cannot be reached
Target-size search applies to JPEG, WebP and AVIF, formats with a quality dial to turn. PNG is lossless and has no such dial, so a PNG kept as "same format" is re-encoded once at a fixed setting and the KB target is ignored; switch the output format to JPEG or WebP first if your source is a PNG. On the other end, an unusually large source photo can still exceed the limit even at the lowest quality the search will try; resizing it down first with the image resizer, then compressing, usually clears that last gap.
The tools used in this guide
- Compress imagesReduce image file size without uploading. Quality slider or target file size in KB. Batch supported.
- Resize imagesResize your images (JPEG, PNG, WebP, AVIF) without uploading them.
- Crop imageCrop your images with an interactive preview, drag and resize the crop area. No upload.
- Convert HEIC to JPGConvert iPhone HEIC/HEIF photos to JPG or PNG without uploading them.
Frequently asked questions
Will the downloaded photo be exactly 100 KB?
It will be at or under 100 KB, not an exact byte count. The search stops at the highest quality it found that still fits the limit, which is usually a little under it (97 to 99 KB for a 100 KB target is typical). Portals that state a maximum, not an exact figure, accept this without issue.
Can I compress a PNG down to a 100 KB target?
Not directly: PNG is lossless and has no quality setting for the search to adjust, so target-size mode has nothing to tune on a PNG kept in its original format. Change the output format to JPEG or WebP first (the format selector sits above the mode toggle); either format compresses with a quality dial the search can use to hit your limit.