Every upload form seems to invent its own number — 20 KB here, 200 KB there, 2 MB somewhere else — but the underlying method for reliably getting any file under any stated limit is exactly the same, whether the file is an image or a PDF. Once you have the process down, the specific number stops mattering much.
The general process
- Read the requirement precisely. Note the exact limit, the required format, and whether dimensions or DPI are also specified — get all of it before starting, not partway through.
- Start from the best available source. A clean original gives a better result at any target size than an already-compressed or already-resized copy.
- Resize first if the target is very small relative to the source. For images especially, pixel dimensions matter more than compression once the gap between current size and target is large.
- Compress next. Start at a light or medium setting and increase only as needed — do not default to the strongest setting out of caution.
- Check the actual downloaded file, not a preview. Confirm the real file size on disk matches the requirement before uploading.
Matching the tool to the file type
- PDF: the PDF Compressor for size, Split PDF to remove unneeded pages if compression alone is not enough.
- Photo or scan as an image: the Image Compressor, with resizing to exact dimensions first if the target is very tight.
- A document you are building fresh: export at a lower quality setting from the source tool (Word, a design tool, a slide deck) before ever reaching for a separate compression step.
A rough sense of what different limits actually mean
It helps to know roughly how demanding a given number is before you start, so you are not surprised by how much work it takes:
- Under 50 KB for an image almost always requires resizing the pixel dimensions down significantly, not just compressing.
- 200 KB–1 MB for a PDF is comfortable for most scanned documents and reachable with compression alone in most cases.
- Several MB is generous enough that only unusually large, image-heavy files need any real work at all.
What to do when the target genuinely cannot be reached
Occasionally, a file’s content is simply too dense for the stated limit no matter what you try — a dozen full-page colour photographs squeezed into a 500 KB cap, for instance. When that happens, the honest fix is reducing the content itself: fewer pages, fewer images, or splitting into the specific pieces that are actually required, rather than repeatedly compressing the same file and hoping for a different result each time.
Keeping a personal reference for limits you meet often
If you regularly deal with the same handful of size limits — the same exam board’s photo requirement every year, the same client portal’s upload cap — it is worth writing down the exact settings that worked last time (target pixel dimensions, compression level used) rather than relearning the process from scratch each time the need comes up again.
Frequently asked questions
Is there one setting that works for every size limit?
No single setting fits every case, but the process above — resize if needed, compress starting light, check the real file — works reliably across essentially any target.
Should I always aim exactly at the limit?
Aim comfortably under it rather than exactly at it, since small differences in how a device or browser saves a file can occasionally push a borderline result over on a strict form.
Does the same method work for both images and PDFs?
The principle is identical — resize/trim content, then compress — even though the specific tools differ between file types.
What if a form gives a size range instead of a maximum?
Aim for the middle of the range rather than either extreme, so you are safely within bounds even if there is any small discrepancy in how the size is measured.
Are these tools free?
Yes. No sign-up, no watermark, and files are removed from the server automatically about an hour after processing.