Shrink a photo or image to 50KB or less for upload limits on forms, shops and communities.
"50 KB" is a ceiling of 50 × 1,024 = 51,200 bytes. For a small photo that is room enough to keep the Balanced quality 0.80 without any search: the 512 × 512 NASA photo came out as a 45,813-byte JPG with SSIM 0.9785. The tool picks the candidate that looks closest, not the smallest — here the JPG beat a 32,200-byte WebP that scored 0.9749. JPG, PNG or WebP files already under 50 KB are returned unchanged, and a form that counts 50 KB as 50,000 bytes needs 48 in Target size.
Drop image files hereProcess many files at onceNo upload · processed on this device
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Each format is first encoded at the level's quality. Only if that exceeds 51,200 bytes does the quality search start. For the 512 × 512 fixture both JPG and WebP at 0.80 fitted at once, so the choice came down to the score: JPG 0.9785 against WebP 0.9749. The target is a ceiling, not a goal — the tool does not raise the quality to fill the remaining 5 KB.
How many pixels fit depends on how much loss you accept. On the fixture, WebP at 0.62 bits per pixel scored 0.96 and JPG at 1.40 bits per pixel scored 0.98. Applied to 51,200 bytes (409,600 bits) that is roughly 0.29 megapixels at the higher score (about 624 × 468) and 0.66 megapixels at the lower one (about 941 × 705).
When the dropped file itself fits and is a format Auto can write, it competes with a perfect score — that is why the 40,240-byte JPG below was returned untouched.
Ceiling
The largest allowed size; results can be well below it.
Bits per pixel
File size × 8 ÷ pixel count; a rough measure of how hard a picture is compressed.
Original kept
The dropped file fits and scores 1.0, so no re-encode can beat it.
Three inputs, one 50 KB target (measured)
Balanced level, Auto format, Chromium 153, 2026-09-28; all three are the 512 × 512 NASA photo in different files.
Target 50 KB = 51,200 bytes
astronaut.png 791,555 bytes -> JPG q0.80 45,813 bytes SSIM 0.9785
(WebP q0.80 32,200 bytes, SSIM 0.9749, lost on score)
astronaut.jpg 75,758 bytes -> JPG q0.80 44,435 bytes SSIM 0.9822
astronaut-q75.jpg 40,240 bytes -> original kept, already under 51,200
Room at 0.62 / 1.40 bits per pixel: 0.66 / 0.29 megapixels
Shrinking was also allowed in a second run: none of the five smaller widths scored higher, so the results above did not change.
Entering the right limit
The form says
Target size to enter
Largest file you get
50 KB, counted as 1,024 bytes
50 (preset)
51,200 bytes
50 KB, counted as 1,000 bytes
48
49,152 bytes
50 KB and JPG only
50, Output format JPG
On the fixture the same JPG as Auto chose
50 KB, fill it with quality
50, level High quality
Starts at 0.92 before searching down
Check the result
Read the size in the result list (1,024-byte KB) and the exact byte count in your file manager.
Look for "kept" in the result line: the original was already small enough, which is not an error.
Check faces and fine print at 100 %.
Troubleshooting
Symptom
Likely cause
How to check
Fix
The file is far below 50 KB
The target is a ceiling; Balanced starts at 0.80 and never goes higher
Result line shows e.g. 45 KB
Choose High quality to start at 0.92
The form rejects a "50 KB" file
The form counts 50,000 bytes
Exact bytes in file properties
Enter 48 as Target size
"Target size not reached" on a phone photo
Several megapixels do not fit in 51,200 bytes
Warning under the file
Allow smaller dimensions or resize to about 900 px wide first
Nothing changed
The file was already under 50 KB and returned as it was
A photo saved as PNG usually fits once it is a JPG at quality 92.
What this page does not cover
Quality is never raised above the chosen level to use the whole budget.
Similarity is judged on a copy at most 512 px long; check fine print yourself.
Versions and sources
Measured on 2026-09-28 in Playwright Chromium 153 by calling src/compression.js with the options src/task/compress.js passes for ?kb=50, with and without shrinking, on tests/fixtures/astronaut.png and two Pillow JPGs of it (quality 92 and 75). The pixel estimates are arithmetic from those measured densities, not measurements of other photos.
Several quality and format candidates are encoded until one fits 50KB; each result is decoded again and compared (SSIM) so the best-looking one wins. You see the real file size before downloading.
Resolution is kept by default. Only if the target cannot be reached, opt in to shrinking the dimensions.
Your file is never uploaded — it is processed inside this browser.
Example generated with this tool. ZIP tools show their preview; inspect the downloaded archive for every file.
Compress image
Set a size limit, then check the actual result.
How it works
Open the source file
Choose the processing mode and settings
Run, inspect the result and download
Supported formats
PNG / JPG / WebP / AVIF / HEIC → PNG / JPG / WebP — Input decoding and output encoding depend on browser support. Animated inputs are rejected; select a still frame first.
What this tool does
Auto compares actual browser codec outputs using a sampled visual metric and target-size search. Alpha-aware format selection; optional dimension reduction.
Implementation and verified quality
advanced · browser codecs / proxy SSIM candidate search. Quality qualification is in progress. Pro/Flagship quality has not been established.
Before you export
Actual device memory, storage and codec support. Tested examples are evidence, not a guarantee for every file.
Frequently asked questions
What determines the supported size?
Actual device memory, storage and codec support. Tested examples are evidence, not a guarantee for every file.
Are my files uploaded?
This tool processes the files you open on your device without uploading them. Images you explicitly attach to community posts are uploaded separately. Optional engines and models are downloaded from third parties; those requests expose connection information such as your IP address.
Will my work be saved automatically?
No. Images and editing state stay in this tab; media output can use local temporary storage. Changing language preserves your work; reloading, closing the tab, or following a link to another page can clear it.
