K-magpie › Kmagpie Tools › Convert Images
Convert Images
Convert between PNG · JPG · WebP · BMP · ICO. Batch-convert many images at once and download them as a ZIP. Files never leave your browser — no upload, no sign-up.
If you just need a different format, keep this at 90 or above. If shrinking the file is the goal, the image compressor can auto-fit a target size.
JPG and BMP cannot store transparency. Any transparent areas in the original are filled with this color.
One ICO file holds several resolutions at once. For a website favicon, 16, 32 and 48 are plenty.
The aspect ratio is preserved and nothing is enlarged. Images are stepped down gradually for a smooth result without jagged edges.
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Convert between PNG, JPG, WebP, BMP and ICO in batches and download everything as a ZIP. The conversion happens entirely inside your browser, so files are never uploaded. For submissions and forms JPG is the safe pick, for the web WebP, and for transparent backgrounds PNG.
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How to use
Add your images, pick the target format, and press Convert. Results appear per file, and you can download them individually or all at once as a ZIP. Your originals are untouched — a new file is created each time, so if the result is not what you wanted, adjust the settings and press the button again.
Every conversion runs through your browser's Canvas API. Because files never leave your browser, private photos and unpublished material stay private, and with no upload or download to wait for, even dozens of images finish quickly. There are no usage limits and no watermarks.
Which format should I convert to
PNG
Use it when you need a transparent background, or for logos, icons and screenshots where text and edges must stay crisp. It is lossless, so re-saving it any number of times never degrades quality. The trade-off: photos saved as PNG are several times larger than as JPG.
JPG
Best for photos, and it opens everywhere. It is the safe choice when you do not know the recipient's software, when dealing with legacy programs, or when attaching images to official forms and applications. It cannot store transparency — transparent areas get filled with the color you pick above.
WebP
25–35% smaller than JPG at the same visual quality, with transparency support on top. For images going on a website it is usually the right answer. Older programs, some document editors and the occasional upload form still reject it, though, so keep files meant for submission in JPG.
BMP
Completely uncompressed, so files are enormous. Use it only when some industrial or legacy software insists on BMP. Not recommended for anything else.
ICO
The format for website favicons and Windows application icons. One file can carry multiple resolutions — the browser tab picks the 16px version, a desktop shortcut picks 48px, and so on. Non-square images are centered with their ratio preserved, and the leftover space is filled with transparency.
What about iPhone HEIC photos
HEIC, the iPhone's default photo format, cannot yet be read by browsers, so this tool cannot convert it. That goes for nearly every browser except Safari. The most reliable fix is a one-time settings change on the iPhone so future photos are saved as JPG.
Go to Settings → Camera → Formats → Most Compatible. For HEIC photos you have already taken, set Settings → Photos → Transfer to Mac or PC (at the bottom) → Automatic, then transfer over a cable — the iPhone converts them to JPG on the way out.
Troubleshooting
My transparent background turned white
You most likely converted to JPG or BMP — neither can store transparency. To keep the transparent background, pick PNG or WebP. To fill with something other than white, change it in the color picker.
My GIF stopped moving
Only the first frame is imported. Converting animated GIFs while keeping the animation is not supported.
Converting to PNG made the file much bigger
That is normal. PNG is lossless, so a photo stored as PNG is several times larger than as JPG. Keep photos in JPG or WebP, and save PNG for images that need transparency or contain lots of text and line art.
A site rejected my converted file
Plenty of sites still refuse WebP or BMP. If it is for an upload form, try converting to JPG instead. If it was rejected for being over a size cap, the image compressor can fit it under a target size.