Compress Image to 300KB — Free, Fast & Private
A 300 KB limit almost always means a form, not a website. It is the upper edge of the band for UPSC’s photograph and its triple signature, for the GATE signature, and for the UAE visa photograph. What those forms have in common is that 300 KB is only half of the rule: each one also names a minimum, and an over-compressed file under that minimum is refused just as firmly as one over the top.
What fits in 300 KB — measured on this page
We dropped five real files on the compressor above and kept what it handed back. 5 of 5 came out under 300 KB.
| File | Before | After, on this page | Under 300 KB? |
|---|---|---|---|
| 12 MP phone photo | 4032 × 3024 px · 3.73 MB | 4032 × 3024 px · 274.1 KB | Yes |
| Portrait / headshot | 3264 × 4653 px · 2.25 MB | 3264 × 4653 px · 286.3 KB | Yes |
| Scanned handwritten page | 3349 × 4281 px · 2.17 MB | 3349 × 4281 px · 288.4 KB | Yes |
| Scanned signature | 2041 × 617 px · 109.1 KB | 2041 × 617 px · 102.1 KB | Yes |
| Screenshot (PNG) | 1280 × 800 px · 88.1 KB | 1280 × 800 px · 108.8 KB — larger than the original (PNG made into JPG) | Yes |
Measured 2026-10-06 in Chromium 145.0.7632.6 with this page’s own settings. The photos are public-domain and CC0 files from Wikimedia Commons; the screenshot is our own. Sizes read as the tool shows them (1 KB = 1,024 bytes); the target itself is 300,000 bytes, which is under 300 KB on either reading.
Where a 300KB ceiling comes from
| Upload | File size | Pixels |
|---|---|---|
| UPSC photograph | 20–300 KB | 550–1000 px each side |
| UPSC signature (signed three times) | 20–300 KB | 350–500 px each side |
| GATE signature | 3–300 KB | 250 × 80 to 580 × 180 px |
| UAE visa photograph | 20–300 KB | 43×55 mm, which is 508×650 pixels at 300 DPI |
UPSC states the rule in one sentence: “Each of the scanned images of the Photograph / Signature should not exceed 300 KB and must not be less than 20 KB in size.” Notice that the photograph and the signature share the same band but not the same pixel range — the signature stops at 500 pixels. Our UPSC page handles both files with their own pixel checks, and the GATE signature tool enforces GATE’s aspect ratio, which this general-purpose page does not.
What 300KB buys at each pixel size — the arithmetic
A file-size limit only means something next to a pixel count, because what a compressor really spends is bytes per pixel. An uncompressed colour pixel takes 24 bits (8 each for red, green and blue). Divide 300,000 bytes by the pixels in each of these uploads and you can see how hard the compressor has to work:
- UPSC photograph at its 1000 × 1000 maximum: 1,000,000 pixels, so 300,000 × 8 ÷ 1,000,000 = 2.40 bits per pixel.
- UPSC photograph at its 550 × 550 minimum: 302,500 pixels, so 7.93 bits per pixel.
- UAE visa photo at 508 × 650: 330,200 pixels, so 7.27 bits per pixel.
- GATE signature at its 580 × 180 maximum: 104,400 pixels, so 22.99 bits per pixel — close to the 24 of a pixel stored with no compression at all, since the raw image is 313,200 bytes.
- An untouched 12-megapixel photo (4000 × 3000): 12,000,000 pixels, so only 0.20 bits per pixel.
Two conclusions fall out of those numbers. At the sizes the portals actually ask for, 300 KB is a generous budget, and the ceiling is rarely the problem — for a GATE signature it is barely a limit at all, and the real risk is undershooting the 3 KB floor. The opposite holds for a full-resolution phone photo: squeezing twelve million pixels into 300,000 bytes leaves so little per pixel that the compressor has to give something up. That is why the order of operations matters, which the next section covers.
How this page reaches 300KB, and when it changes the pixels
The compressor first lowers JPEG quality at the photo’s full pixel size, looking for the highest quality that still fits under 300,000 bytes. Only if even its lowest quality setting misses does it reduce the pixel dimensions — and when it does, it says so and shows you the new width and height. It does not promise to keep full resolution, because for a large photo that is sometimes impossible at this size.
For a form upload, a better route is to do the resizing yourself before compressing. Crop and resize to the form’s pixel range first — the crop tool or passport-size resizer will do it — and then bring the smaller file here. At a pixel count inside UPSC’s or the UAE’s range, the arithmetic above shows there is room under 300 KB for a high quality setting, so you are choosing the framing yourself instead of letting the compressor decide how many pixels to drop.
Check the pixel size after compressing as well as the kilobytes. A file that fits under 300 KB but measures more than 1000 pixels on a side is still outside UPSC’s rule, and the file-size counter will not warn you about that.
The two signatures that share this ceiling
UPSC and GATE both allow a signature up to 300 KB, but they ask for very different images. UPSC wants the name written three times: “Applicants are required to sign three times (one below the other) on a plain white paper using a black ink.” That makes a roughly square block of ink, and its pixel range (350–500 px each side) is square as well. GATE wants a single signature in a wide strip, with a height-to-width ratio between 1 : 2.75 and 1 : 3.75, and adds its own rules: signature covers 70–80% of the image; black or dark blue ink only; not in all capitals, not initials, not a digital signature.
The file-size figure is the same; the crop is not. Sign, photograph and crop for the exam you are applying to first, then compress. A GATE-shaped strip uploaded to UPSC, or the reverse, can sit comfortably under 300 KB and still be the wrong picture.
Failing at the bottom of the band
It sounds unlikely when the target is 300 KB, but small files get refused here too. UPSC’s floor is 20 KB and the UAE visa floor is 20 KB. A signature photographed on white paper and cropped tight to the ink can come out under either, simply because there is so little in it. GATE’s signature floor is lower, at 3 KB, but the same thing applies.
If your file is already under the floor, do not compress it further. Re-scan or re-crop with a little more margin, or export at a higher quality, so the file grows back inside the band. A target of 300 KB is a ceiling to stay under, not a size the file has to reach.
One unit caution while you are near the top: this page counts 1 KB as 1,000 bytes, so its 300 KB is 300,000 bytes. A validator that counts 1,024 bytes to the kilobyte allows 307,200 bytes for the same number, so a file under 300,000 passes both readings.
Everything runs in your browser. Your photograph and signature are never uploaded to a server while you compress them.