Exam registration, scholarship and government portals often set both a minimum and a maximum, for example 20 to 30 KB for a photo or 10 to 20 KB for a signature. Getting under the maximum is easy. Staying above the minimum takes a little care, because over-compressing makes the file too small to be accepted.
This page sets the target at 30 KB. The compressor aims just under it, and the preview shows the final size so you can check it falls in the required range before you download.
Why ranges are harder than a single limit
A single maximum is simple: compress until you are under it. A range has two sides. Too large and the portal rejects the file. Too small and the portal also rejects it, usually with a message about minimum size or poor quality.
The reason portals set a minimum is to prevent unreadable images. A 5 KB photo is likely to be a tiny thumbnail, and a face in it may be impossible to identify. Setting a range keeps the image large enough to be useful.
In practice, aim for the top of the range. If the limit is 20 to 30 KB, target about 28 KB. That leaves you a safe gap above the minimum and below the maximum.
Steps to land inside 20 to 30 KB
First, crop the photo to the required ratio, for example 3:4 for a passport-style picture. Cropping removes pixels you do not need, which also reduces size.
Second, set the target at 30 KB on this page and add the photo. The tool tries a quality that fits, and if the picture is still too large, it reduces pixel dimensions.
Third, read the size in the preview. If it shows between 20 and 30 KB, download it. If it is below 20 KB, raise the target a little and run again. If it is above 30 KB, lower the target and run again.
Signature images in the same range
Signatures behave differently from photos. A dark signature on a white background has few colours and compresses very well. A 600 by 200 pixel signature often lands at 8 to 15 KB at a decent quality.
If the portal asks for a signature between 20 and 30 KB and yours is smaller, do not pad the file. Increase the pixel dimensions slightly, for example to 900 by 300, or raise the quality, and run again.
Scan or photograph the signature on plain white paper in good light. Shadows and creases add noise, which increases the file size and lowers the sharpness.
Common reasons for rejection
Wrong format: the portal wants JPG and you uploaded PNG or WebP. Save as JPEG, which this tool does by default for size targets.
Wrong dimensions: the portal wants a specific width and height. Check the preview dimensions.
Wrong file name: some portals reject names with spaces or special characters. Use a plain name such as photo.jpg.
Wrong size on disk: some operating systems show size in KiB or MB with rounding. Check the number in the tool's preview rather than the file manager.
A worked example: a passport photo for an exam form
An exam portal asks for a passport photo between 20 and 30 KB, JPEG, with a minimum size of 200 by 230 pixels. Your picture is a 3 MB phone photo of 3,000 by 4,000 pixels. First crop it to the 3:4 ratio, with the head and shoulders filling the frame.
Next, add it to this page with the target at 30 KB. The tool reduces the long edge to about 600 pixels and brings the quality to about 60. The preview shows 27 KB at 450 by 600 pixels. That is inside the range and above the minimum dimensions.
If the preview had shown 18 KB, you would raise the target to 35 KB or choose a larger size and run it again. The aim is a result that is clearly inside the window, not one that sits on the edge.
Why file size and image quality are not the same thing
File size depends on how much information is stored. A noisy photo has lots of fine variation and needs more bytes. A smooth image with a plain background needs fewer. Two photos of the same pixel dimensions can differ in size by a factor of three.
That is why one photo reaches 20 KB at a moderate quality and another needs a much lower quality to get there. If your picture is noisy, a quick noise reduction in an editor before compression often helps more than lowering the quality further.
Colour also matters. Photos with lots of saturated colour carry more data than black and white ones. If a portal does not require colour, a greyscale copy can be much smaller, but check the rules before you do that.
Documents that commonly ask for this range
Government exam registrations in several countries ask for a photo and a signature in the 10 to 50 KB range. University applications may ask for 20 to 100 KB. Visa and e-passport portals often have their own rules for pixel size and file size together.
Banks and financial institutions use similar limits for KYC uploads. A recent photo, a signature and a scan of an ID card may each have a separate limit, so check each field carefully.
Always read the instructions on the portal itself. Limits change between years and between departments, and a form that accepted 50 KB last year may now ask for 30.
Step-by-step for a signature in the 20 to 30 KB window
Sign on plain white paper with a dark pen. Blue or black ink works best. Avoid pencil, which can look faint after compression.
Photograph it in even daylight with the paper flat and the phone directly above. Crop tightly so the signature fills the frame with a small margin.
Add the picture to this page, set the target at 30 KB and check the preview. A tight crop of a signature at 600 by 200 pixels often lands at 10 to 15 KB, which is below the minimum. If so, raise the pixel dimensions or quality, or enlarge the crop slightly, until the size is between 20 and 30 KB.
Check the signature at 100 per cent zoom. The strokes should look clean, with no grey haze around them. If there is haze, retake the photo in better light.
Why portals set both a minimum and a maximum
The maximum protects the portal's storage and speed. Thousands of applicants uploading large photos would be costly. The minimum protects quality, because very small files are usually unusable.
Some portals also check the width and height. A common rule is that the image must be at least a certain number of pixels, even if the file is small. Others check the ratio and reject pictures that are too square or too wide.
Because the rules are checked automatically, a small mismatch means a rejection with no human review. It is worth taking an extra minute to verify every number.
Keeping a record of what you submitted
After you upload, keep a copy of the exact file you submitted. Save it in a folder named for the application, with the date.
Take a screenshot of the confirmation page. If the portal later reports a missing or invalid file, you have proof of what was sent.
If you need to resubmit, start again from the original photo rather than recompressing the compressed file. Each compression step loses a little more quality.
Quick reference: sizes that land inside 20 to 30 KB
A passport-style portrait at about 450 by 600 pixels and quality 60 usually lands in the mid-20s.
A square profile picture at 500 by 500 pixels and quality 65 often lands near 25 KB.
A wide signature at 900 by 300 pixels with dark ink on white often lands near 20 KB.
A thumbnail-style picture at 400 by 400 pixels with a plain background can fall below 20 KB, so raise the size slightly if the portal sets a minimum.
These are starting points, not guarantees. Each picture is different, so always check the number in the preview before you download.
Why a second attempt sometimes works better
The first run uses the settings that fit your target most directly. If the result is outside the range, the second run with a small change often fixes it.
Raise or lower the target by about five KB, not by a large amount. A small change gives a small change in the result.
If a picture is stubborn, crop it more tightly. Removing background pixels reduces the data without touching the subject.
If the file is still just outside the range, try a slightly different dimension. Many portals accept any size inside the range, so there is no need to match a specific pixel count.
JPEG quality or pixel dimensions — which one should you reduce first?
Most people reach for the quality slider first because it is the obvious lever. That instinct is usually right for a portrait, but it is wrong for a scanned document or a line-art signature.
For a portrait, pixels carry most of the file weight. A face at 1200 by 1600 pixels holds a lot more data than the same face at 600 by 800 pixels, and a human eye cannot tell the difference at passport-photo sizes. So for a portrait, drop the dimensions first — cut them in half and you often knock the file size down by about 70 percent before you touch quality at all.
Quality controls how much the JPEG codec smooths out detail. Below about 50 it starts to leave visible blocks on smooth surfaces like skin and sky. Between 55 and 75 the result looks clean on screen and in print. Start there and only go lower if the file still does not fit.
For a signature or a document scan the math flips. Those files are mostly white space, and the JPEG codec compresses white runs very efficiently regardless of quality. Reducing dimensions on a signature too aggressively makes the ink lines thin and broken, which can cause automated form readers to reject the file as unreadable. Keep the dimensions wide enough that the strokes look solid — usually at least 600 pixels across — and use quality to control the size instead.
A practical rule: if the subject is a person or a scene with gradients, halve the dimensions first. If the subject is ink on white, keep the dimensions and lower quality first. Either way, check the preview before downloading — the preview size shown is the exact number the portal will see.
Scanned documents versus phone photos — why they behave differently
A phone camera captures light and saves a continuous-tone JPEG, typically around two to five megabytes for a well-lit portrait. The sensor has a dynamic range of several stops, so even a plain background has subtle variation in brightness and colour. That variation costs bytes.
A flatbed scanner captures a document under controlled light, and a printed page is mostly flat white. JPEG handles large areas of near-identical colour extremely well, so a full A4 scan at 200 dpi can compress down to under 50 KB without visible loss. That is why scanned certificates and ID photocopies often reach the 20 to 30 KB range with almost no effort.
Phone photos of documents present the worst of both worlds. The camera introduces lens distortion, shadow gradients from overhead lighting, and colour cast from the room. That noise fights the compressor and leaves the file larger than a clean scan would be at the same visible quality. If you are photographing a paper document with your phone, flatten the paper, stand directly over it, and use as much natural light as possible to get a clean, evenly lit shot before you compress.
Selfie and portrait photos taken on a phone almost always need both a dimension reduction and a quality reduction to reach 30 KB. The starting file is large by design — modern phone cameras default to 12 megapixels or more, and portrait mode adds a depth map that inflates the base size further. Strip any metadata or special modes before compressing, and crop the frame to just the face and shoulders so there is less background data for the codec to carry.
In short: scans are already cheap to compress, phone portraits are expensive to compress, and phone document photos sit in the middle. Set your expectations by the source, not by the subject matter.
Five reasons an upload gets rejected and how to rule each one out
File too large is the most common rejection. The portal shows a specific limit, but the number it checks may be the uncompressed buffer in memory, not the bytes on disk. Always check the final size shown in the preview panel — that matches what the portal measures — and keep it a few KB below the stated ceiling rather than right on the edge.
File too small trips up anyone who overshoots the compression. Some portals set a minimum because a very small file is a sign the photo is too blurry or too low resolution to be useful. If the preview shows under 20 KB, raise the target slightly or pick a larger pixel dimension and run again.
Wrong format catches people who save a PNG or WebP and rename it with a .jpg extension. A portal that checks the actual file header will reject it. Use a tool that genuinely produces a JPEG — the download from this page is always a real JPEG regardless of what the original file was.
Dimensions out of range is less common but real. A few government and university portals specify both a KB limit and a pixel size range such as 200 by 200 to 400 by 400 pixels. If your file is within the size range but still rejected, check whether the portal also lists a required pixel dimension and match it.
Session timeout is a quiet failure mode. Some portals have a strict time limit on the upload form, and if you spent several minutes compressing and previewing before clicking upload, the session may have expired. The page may look active but the submission fails silently. If you get an unexplained rejection after a long wait, reload the form, fill it in again, and upload without delay.