Reduce any image below 20KB entirely in your browser. Targets 18KB by default to give a safe margin under strict 20KB portal limits.
Last updated: August 2026
18KB
Default Target
Safe Margin
Under 20KB
JPEG, WebP
Output
Private
No Uploads
Drop image here to compress to 18KB
JPEG, PNG, WebP, AVIF, HEIC. All processing stays in your browser.
Default target is 18KB. If your portal requires a different limit, change the target field above, no need to drop the file in again.
Five steps is all it takes. Everything runs in your browser so there is no waiting for an upload or server processing.
Target defaults to 18KB
Pre-set with a safe margin under a strict 20KB limit. Adjust it if your portal states a different number.
Drop your image
Drag and drop a JPEG, PNG, WebP, AVIF, HEIC or HEIF file onto the tool. No upload happens, the file stays on your device.
Quality check, then dimension fallback if needed
Checks whether minimum quality already fits. For a real photo it often doesn't at 18KB, so the tool steps down the pixel dimensions automatically, in a background worker.
Fine-tune without starting over
Change the target or switch between JPEG and WebP afterward and the tool recompresses automatically.
Download the result
Preview and size stats appear. Download the compressed file immediately.
A 20KB ceiling is one of the strictest file size limits you will encounter on a form or portal. It most commonly appears on signature upload fields and legacy government systems that were built to serve users on very slow internet connections.
Digital signature uploads
Many online forms require a scanned signature image under 20KB. This is the most common real-world reason users encounter this limit, particularly on banking, legal and government forms.
Avatar and profile thumbnail fields
Older portal systems with fixed-size thumbnail slots often cap uploads at 20KB because the image is displayed at very small sizes and does not need high resolution.
Strict legacy government forms
Some state-level government portals in India, Bangladesh and other countries impose a 20KB ceiling on applicant photographs, particularly for older scholarship and subsidy application systems.
Low-bandwidth submission systems
Portals designed for rural or low-connectivity users sometimes enforce very tight file size limits across all uploaded assets to ensure the system remains accessible on slow connections.
20KB works out to roughly 160,000 bits for the entire image. Spread that across even a modest 800 by 600 photo and there's only a tiny fraction of a bit available per pixel. No amount of turning down a quality slider alone gets a real photo down to that budget, since the format still needs some minimum amount of information to describe each block of pixels no matter how aggressive the setting. If you want more control over exactly which dimensions get used, you can also resize the image yourself beforehand.
JPEG compresses in 8 by 8 pixel blocks, and even at the lowest usable quality setting, each block still needs a minimum number of bits to describe it. Once a source photo has more of these blocks than the target byte budget can support, quality alone runs out of room. The only way to shrink the file further at that point is reducing the actual pixel dimensions before compression, not pushing the quality number any lower.
A signature scan or a simple line drawing is mostly flat white background with a small amount of dark line data. JPEG's compression finds huge blocks of nearly identical pixels to describe efficiently, so a legible signature can genuinely fit under 20KB at its original dimensions without needing the aggressive downscaling a full photo would require to hit the same target. If your signature scan came from an iPhone as a HEIC file, it's worth converting it to JPG first, since HEIC decoding support varies by browser.
The tool doesn't guess a single quality number and stop. It checks whether minimum quality already fits your target, and if a real photo still overshoots even at the lowest usable quality, it steps down the pixel dimensions and re-checks until both quality and size land somewhere usable. That's why the same 18KB target can produce very different-looking results depending on what's actually in the source image, a signature keeps its full size and stays sharp, while a busy photo gets both compressed and shrunk to make the same budget. A flat-color screenshot exported as PNG can also be run through PNG to JPG first if you want to check its size before compressing further, and the metadata viewer will show you the exact dimensions and size of any file before or after.
Under 50KB
A slightly more generous margin
Under 100KB
The most common job and ID portal limit
Under 200KB
General online form uploads
Under 500KB
Higher quality documents and photos
Exactly 10KB
A precise target for the strictest portals
Exactly 20KB
A precise target instead of a margin
Exactly 50KB
Precise target for passport and visa photos
Exactly 100KB
Precise target for job portals
Expecting zero visible quality loss on a busy photo
At 18KB, dimension scaling is common for a real photo, unlike looser targets where quality alone almost always has enough room. A signature or line drawing rarely needs this, a full-color photo often does.
Choosing JPEG for a transparent signature or logo PNG
If the source file has a transparent background, JPEG fills it with a solid color. The tool warns about this and offers a one-click switch to WebP, which keeps transparency.
Assuming a file at exactly 20KB will pass
Some portals check for strictly less than 20KB, not less than or equal. That's why this tool defaults to an 18KB target instead of 20KB, to leave real margin.
Not trying WebP for extra quality headroom
WebP compresses more efficiently than JPEG at low quality settings, which matters most at a tight target like this. Switch to WebP if the destination portal accepts it.
Re-dropping the file just to test a different target
That's no longer necessary. Changing the target size field after a result already appears recompresses automatically using the same cached image.
Trying to compress several images at once
This tool handles one image at a time. For a batch of signature scans or ID photos, run each one through individually.
Forms and portals that impose a 20KB ceiling are typically legacy systems built for low-bandwidth environments, or fields designed for small image types such as signature scans and thumbnail avatars. The limit is enforced server-side, so your file must be strictly below 20KB before you submit. Files at exactly 20KB are sometimes rejected because the check is for less than, not less than or equal to.
When a portal specifies a maximum of 20KB, any file smaller than 20KB passes. You do not need to hit exactly 20KB. This tool targets 18KB by default, leaving a safe 2KB margin so your file passes even if the portal measures file size differently or has a slightly stricter internal threshold.
Often, yes, for a real photo. Unlike a looser target such as 500KB or 1MB where quality alone almost always has enough room, 18KB is tight enough that even the lowest usable JPEG or WebP quality setting can overshoot it for a typical photo. When that happens, the tool automatically steps down the pixel dimensions and re-checks quality at the smaller size until both fit. A simple signature scan or line drawing is far less likely to need this, since it has very little visual complexity to begin with.
It depends on the type of image. A scanned signature or simple line drawing compresses to under 20KB with very little quality loss because these images have low visual complexity. A full-color photograph at 18-20KB will show visible compression and reduced dimensions, but will remain clear enough for identity verification and form submission purposes.
JPEG, PNG, WebP, AVIF, HEIC and HEIF are all supported as input. The output is JPEG or WebP only, never PNG. For portal submissions, JPEG is the safer default since it's accepted by essentially every upload system, including older government and banking portals.
JPEG has no alpha channel, so a transparent PNG compressed with JPEG selected has its transparent areas filled with a solid color instead. If the tool detects transparency and JPEG is selected, it shows a warning with a one-click button to switch to WebP, which keeps transparency intact. This matters for scanned signatures exported with a transparent background.
No. Both the quality check and any dimension-scaling fallback run in a background Web Worker rather than on the page's main thread, so the tab stays responsive even while the tool works through several scale steps to hit a tight 18KB target.
Yes. The tool keeps the decoded image cached, so adjusting the target size field or switching between JPEG and WebP after a result already appears triggers an automatic recompress rather than asking you to drop the file in again.
No. The image is decoded to raw pixels and re-encoded during compression, so EXIF metadata, including GPS location and camera details, does not carry over to the compressed file. This is worth knowing if a portal specifically requests metadata-stripped photos.
No, this tool handles one image at a time. For multiple signature scans or ID photos, run each one through individually.
No. All compression runs entirely in your browser using the Canvas API and WebAssembly. Your image never leaves your device. You can verify this by disconnecting from the internet after the page loads, the tool still compresses and downloads your image successfully.
Yes. Even a small reduction from 22KB to under 20KB is handled correctly. The tool finds the highest quality setting, or the smallest dimension reduction, that produces a file below the target, so small reductions like this work just as reliably as large ones. It targets 18KB by default, giving you a comfortable margin below the portal limit.
No sign-up. No uploads. Drop your image above and download the compressed version in seconds.
