How to reduce image size on mobile
Most exam and document uploads happen on a phone these days, and most phone cameras produce photos far larger than any form actually needs — a modern phone easily captures 3-8MB per photo, while forms typically want something between 20KB and 300KB. That's a 20-100x difference to close, and doing it entirely on the phone (without emailing the photo to a computer first) is now the normal way people handle it.
Why phone photos are so large by default
Phone cameras are tuned to capture as much detail as possible for editing and printing, not for small web uploads — high megapixel counts and minimal in-camera compression are a deliberate choice for photo quality, which is exactly the opposite of what a 20-100KB form upload needs. There's no setting on most phones that directly outputs a form-ready file, which is why a separate compression step is needed.
Step-by-step, entirely on your phone
- Open your phone's browser (Chrome, Safari, or any modern one) and go to the Compress Image to KB tool.
- Tap to upload — this opens your phone's photo picker, same as attaching a photo to a message.
- Type the exact KB target your form needs.
- The tool compresses the photo right there in the browser tab and shows you the final size.
- Download — it saves to your phone's normal Downloads or Photos location, ready to upload to the form.
Does this work the same on Android and iPhone?
Yes — since the tool runs inside the phone's own browser rather than as a separate app, the steps are identical on Android and iPhone. The only small difference is where the downloaded file lands (a Downloads folder on Android, typically the Files app or Photos on iPhone), which is standard behaviour for any browser download on that phone, not something specific to this tool.
A tip for slow mobile connections
Since nothing is uploaded to a server — the whole compression happens inside the browser tab using your phone's own processor — this works the same on a weak or patchy mobile data connection as it does on fast Wi-Fi, unlike tools that require uploading your photo somewhere first.
Why the same photo shows a different file size on different phones
Two phones can save what looks like an identical photo at very different file sizes, because camera apps differ in their default resolution, compression format (some now save HEIC instead of JPEG by default), and internal quality settings — none of which is visible just by looking at the picture. This is why reducing image size directly in the browser, working from the actual file rather than a device-specific setting, gives a consistent result regardless of which phone or camera app produced the original photo.
If your phone saves photos in HEIC format and a portal only accepts JPEG or PNG, that format mismatch — not the file size — is usually the actual reason an upload gets rejected, so it's worth converting the format first before assuming a compression problem.
Frequently asked questions
Do I need to install an app?
No, it works directly in your phone's browser — nothing to install.
Will this work on a basic/older phone?
Yes, as long as the phone has a reasonably modern browser (most Android and iPhone browsers from the last several years work fine).
Can I compress multiple photos at once on mobile?
Yes, you can select several photos from your phone's gallery in one go, and each is compressed independently to the same target.
Why does my phone photo get rejected even though it looks fine?
Some phones save photos in HEIC format by default, which many portals don't accept even if the file size and quality are fine — converting to JPEG or PNG usually fixes this.