What this tool does
You choose a photo, optionally reduce its width, and save it again as JPEG, WebP or PNG. The typical uses are turning a multi-megabyte photo into a few hundred kilobytes for a blog or online shop, or getting an image under the size limit of an email or chat attachment. Internally the browser decodes the file, redraws it onto an HTML canvas at the size you chose, and then re-encodes it with canvas.toBlob. No external library is involved; it relies only on features built into your browser.
Where is the image processed?
The code on this page contains nothing that uploads your file over the network. The selected file is read by the browser through a temporary address created with URL.createObjectURL, and the result is built as a Blob in browser memory and attached to the download link. In other words, the contents of your photo do not leave your device. The page itself is an ordinary web page, so site-wide things such as access logs or advertising scripts behave as they do on any page of this site, separately from the image processing.
How size and quality decide the file size
File size roughly follows the number of pixels, and on top of that sits the compression method of the chosen format and your quality setting. Cutting the width in half also cuts the height in half, so the pixel count falls to a quarter. That makes reducing dimensions far more powerful than nudging the quality slider. This tool only shrinks images that are wider than the limit; it never enlarges a smaller image. The height is scaled by the same ratio and rounded, so the aspect ratio is preserved.
The table below uses a 4:3 photo to show pixel counts at common widths and the approximate memory the browser needs once the image is decoded at 4 bytes per pixel. It is a measure of working memory, not of file size.
| Resolution | Pixels | Decoded memory | Share of a 12 MP photo |
|---|---|---|---|
| 480 Γ 360 | 172,800 | 675 KB | 1.4% |
| 768 Γ 576 | 442,368 | 1.69 MB | 3.7% |
| 1080 Γ 810 | 874,800 | 3.34 MB | 7.3% |
| 1600 Γ 1200 | 1,920,000 | 7.32 MB | 16.0% |
| 4000 Γ 3000 (12 megapixels) | 12,000,000 | 45.78 MB | 100.0% |
Reducing a 4000 Γ 3000 photo to a 1080 px width gives 1080 Γ 810, which is about 7.3 percent of the original pixel count. Limiting a 1920 Γ 1080 screen capture to 1600 px gives 1600 Γ 900. If an original is 3.20 MB and the result is 420 KB, the reduction shown is 1 β 420 KB Γ· 3.20 MB, rounded to 87 percent. (KB and MB on screen use 1,024-based units.)
JPEG, WebP or PNG: which one?
- JPEG: lossy compression. A sensible default for photographs, and it opens almost everywhere. It cannot store transparency.
- WebP: supports lossy and lossless compression plus transparency, and often produces smaller files than JPEG at similar visual quality. Some older programs and upload forms still do not accept WebP.
- PNG: lossless, so quality is preserved, but photographs can become much larger. A good fit for logos, screenshots and images with transparent backgrounds. When PNG is selected here the quality value does not apply; only reducing the width shrinks the file.
Limits and what happens during conversion
- Re-encoding loses detail. JPEG and WebP are lossy, so every save discards a little more information. Re-saving an already compressed JPEG at low quality can produce visible blocky noise. Keep your original file.
- The file can get bigger. Converting a small, heavily compressed JPEG to PNG, or choosing a high quality value, can make the result larger than the original. The reduction then shows 0 percent and a note appears under the result.
- Transparency. Converting a transparent PNG to JPEG fills the transparent areas with white, because a white background is painted first. Choose WebP or PNG to keep transparency.
- Metadata is dropped. Because the image is redrawn on a canvas, details such as shooting time, camera model and GPS location (EXIF) are not written to the new file. That can be a helpful side effect if you are worried about location data, but it is unsuitable if you need copyright or other metadata to remain. Most current browsers apply the photo orientation when drawing; very old browsers may save a sideways image.
- Color profiles. There is no guarantee that a wide color gamut such as Display P3 is carried through, so colors can shift slightly.
- Animated and vector images. An animated GIF or WebP is saved as a single still frame, and an SVG is rasterized into a bitmap.
- Files the browser cannot open. Formats your browser cannot decode, such as HEIC or camera RAW in some environments, fail to load and a message is shown. Export to JPEG first or use another tool.
- Size ceiling. This page sets no file size limit of its own. The practical limits are your device memory and the maximum canvas size of your browser, which vary by browser and device and tend to be lower on phones. If no result appears for a very large image, choose a smaller width.
- Browsers without WebP saving. A browser that cannot encode WebP may fall back to another format. The note under the result then names the format actually produced, and the file extension is adjusted to match.
Suggested settings by situation
For photos placed in web pages, start with a width of 1080 to 1600 px, WebP or JPEG at roughly 75 to 85 percent, and check the result by eye. Screenshots full of text tend to blur around the letters in JPEG, so PNG or WebP at 90 percent or higher is usually better. For chat apps, around 1080 px is often plenty. For printing, do not shrink the file at all; use the original. Rather than choosing by the reduction percentage alone, zoom into the preview and make sure that text, faces and fine detail are still acceptable before you download.
Frequently Asked Questions
Is my uploaded photo stored anywhere?
No. It is processed only in your browser's memory and is not uploaded or saved. Closing or reloading the tab discards the result.
Can I convert several images at once?
Currently only one image at a time. Keep the same settings and choose the next file to repeat the same conversion.
What if the quality looks too degraded?
Raise the quality slider to 80 to 90 percent or choose a larger maximum width. You can also keep the original size and only lower the quality. If it still looks poor, try PNG, though the file may grow.
The result is larger than my original. Why?
It is common when the original is already efficiently compressed or when PNG is chosen. Switch to JPEG or WebP, lower the quality, or reduce the width. If the result is still larger, simply keep using the original.
Does it remove the location data from my photo?
Because the image is redrawn on a canvas, EXIF data including GPS is not written to the output. That is a side effect rather than a dedicated feature, so for sensitive photos it is worth checking the properties of the saved file yourself.
Why does the quality slider do nothing for PNG?
PNG is lossless and has no quality setting. To shrink a PNG, reduce the width, or switch to JPEG or WebP.
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