Read the complete rule beside the upload box
A small attachment field might specify a maximum size, a minimum size, allowed formats and a particular image shape. Write those requirements down together. Do not borrow a size or dimension rule from another application simply because its upload screen looks similar.
For a signature sample, profile image or other small item, the relevant detail needs to remain clear at the required dimensions. For an official photograph, check the service's rules about editing before changing anything. The 100KB target on this page is a technical option, not an official requirement for any named application.
Use the original with the cleanest useful detail
A sharp, well-lit source gives compression a better starting point than a blurry photograph with paper texture and shadows. Open the file and check the content that actually matters: thin strokes in a signature, individual digits or the edges of a stamp. If those details are already unclear, a smaller export will not restore them.
Remove irrelevant surrounding material only when cropping is permitted and can be done without losing required edges or context. This page does not provide a crop editor. Prepare the intended source in an appropriate image application first, then return here. Keep the untouched original so you can revise the preparation if needed.
What happens when you run the target
Choose one supported file and press Process files. The input may be a JPG, PNG, WebP, decodable HEIC or readable PDF, subject to the tool's input limits. Images can be re-encoded and reduced in pixel dimensions while the tool tries to reach the byte ceiling. That process can affect appearance.
For PDFs, the attempt is limited to lossless repacking. It does not shrink embedded scan images or rebuild the pages as low-resolution pictures. A detailed scanned PDF is therefore unlikely to offer the same reduction opportunities as a photograph processed directly.
If the file is already strictly below the tool's target, it can be returned without changing its bytes. That avoids an unnecessary extra round of compression. An unchanged small HEIC or WebP is still that format; being under the size limit does not convert it into a JPG accepted by another website.
Pay attention to the narrow byte difference
The difference between 100,000 and 102,400 bytes is only 2,400 bytes, but a strict upload check can care about every one of them. A result of 101,000 bytes fits this tool's binary target and exceeds a decimal 100KB cap. Rounded labels can conceal that distinction.
Read the saved file's exact byte count in your device's file information. Make My Files Work currently rounds its KB and MB display, so compare the byte count with any precise limit given by the receiving website. Do not assume that a result marked ready by this tool is below a different ceiling. Leave a reasonable margin where the source and readability allow it.
Keep the minimum image dimensions in view
Automatic resizing may lower the pixel width and height. That can help a small byte target, but it can also put the image below a minimum required by the destination. Check the resulting dimensions as carefully as its file size.
For example, a form could require a particular minimum width as well as a maximum byte count. A compressed picture that is only half that width solves one problem while creating another. This page does not lock a destination's minimum dimensions during processing. Compare the final result with the complete set of instructions before attaching it.
Choose a background only when it is suitable
The transparency control is relevant when processing would produce JPG and the source may contain clear areas. You can keep the protective refusal or explicitly choose white or black. Check the original artwork before choosing: a white signature or pale mark intended for a dark background can disappear against white.
That choice is about how transparent areas are represented, not a way to erase the photographed background. A grey sheet of paper or a shadow recorded in the pixels remains part of the picture. Use a clean original capture when that background is causing the difficulty.
Examine fine lines instead of judging the thumbnail
Small previews can make a heavily compressed picture look acceptable. Open the downloaded image at a useful size and inspect fine strokes, punctuation, dates and any identifying number. Jagged edges, merged characters or missing pale lines can make a small file unusable.
With PNG, a reduction may come from fewer pixels rather than a lower lossy quality setting. With JPG or WebP, encoding changes can also affect detail. There is no universal percentage that preserves every signature or scan. Stop when the information stops being reliably readable, even if the resulting byte count is attractive.
When a PDF cannot reasonably fit
A multi-page scan with substantial detail may not fit this very small allowance using the available method. The tool will report an unreachable target rather than supply an oversized file labelled as a success. Repeating the same attempt does not change the contents that need to be stored.
Check whether the upload field is actually intended for the complete PDF or a different item. If the whole document is required, ask the receiving organisation about a suitable alternative. Re-exporting from the original document can help in some cases, but removing required pages or replacing a signed original with a tiny screenshot can make the submission unsuitable.
Troubleshoot the next error precisely
Once the file fits, a rejection may concern its format, encryption, dimensions or the website session. Select the new download explicitly; the upload field may still contain the old file. Read the new error before compressing again.
The tool processes the file locally in your browser and does not send it to a Make My Files Work server. Inputs are limited to 25 MiB, with additional image-pixel and PDF-page safeguards. A refusal can therefore concern the source's complexity rather than the requested final size. Start from a suitable authorised source instead of repeatedly changing the filename.
Questions that come up
Does this guarantee a file below decimal 100KB?
No. The built-in ceiling is strictly below 102,400 bytes. A decimal 100KB rule is 100,000 bytes. Measure the output against the destination's actual number and prepare a smaller readable copy if required.
Can I make an image exactly 100KB?
The tool aims below its ceiling; it does not pad a smaller file to an exact size. Most maximum-size checks do not need exact equality. If there is also a minimum size, read and check that separate requirement.
Should I keep compressing until the upload works?
Only if excess bytes remain the actual problem. Once size is within the right limit, inspect format, pixel dimensions and the precise rejection message. Further reductions can damage useful detail without addressing the cause.