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BMP to PNG Converter: Shrink Bitmaps Losslessly

Convert Windows BMP bitmaps to PNG in your browser. Lossless, no uploads. Cuts the bloat of uncompressed bitmaps while keeping every pixel intact.

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How It Works

A 1920x1080 BMP is roughly 6 to 8 MB no matter what it shows, because classic Windows bitmap stores every pixel raw, three or four bytes each, with no compression. PNG holds the exact same pixels but runs DEFLATE over them, so a screenshot or diagram often drops to a fraction of the size. Most people end up here because some tool still emits .bmp (old Windows utilities, scanners, MS Paint, embedded device exports) and the modern web, email clients, and chat apps either choke on it or balloon the page weight. Everything runs in your browser. The bitmap is decoded by the browser's native image pipeline into an RGBA raster, drawn pixel-for-pixel onto a canvas, then re-encoded as PNG. No file is uploaded, so internal screenshots, scanned documents, or IDs never leave your machine. Both formats are lossless, so not a single color value shifts in the round trip. The size win comes entirely from PNG compressing the runs of repeated and predictable pixels that BMP leaves uncompressed. Two honest caveats worth knowing: an opaque BMP has no transparency to recover, so the PNG stays opaque (PNG supports an alpha channel, but this won't invent one). And because the canvas decodes to RGBA, an indexed or grayscale BMP comes out as a truecolor PNG with identical pixels, not a re-packed palette image.

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Key Features

  • No file uploads required - works offline
  • 100% privacy focused - client-side processing
  • Browser powered - no software installation
  • Fast processing - WebAssembly technology
  • Free forever - no premium accounts

Supported File Formats

.bmp

Output Format: PNG

Technical Specifications

input Format BMP (Windows Bitmap, .bmp)
output Format PNG (Portable Network Graphics, .png)
compression Type Lossless DEFLATE (BMP is uncompressed; PNG packs the same pixels)
quality Retention Lossless, every pixel value preserved exactly
color Space Support sRGB; reads 24/32-bit truecolor, 8-bit indexed, and grayscale BMP; outputs truecolor RGBA PNG
max Resolution Limited only by your device's memory
processing Time Instant, runs in your browser

Key Benefits

  • Cuts the bloat of uncompressed bitmaps without altering a single pixel value
  • Runs entirely in your browser, so confidential scans and screenshots are never uploaded
  • Produces a PNG that every browser, CMS, email client, and chat app reads natively
  • Lossless in both directions, so converting carries zero risk of degradation
  • No watermarks, no account, no file-size paywall
  • Preserves exact dimensions and colors, with no resizing or recompression artifacts

Common Use Cases

  • Shrinking BMP exports from legacy Windows software before emailing or archiving them
  • Converting MS Paint or scanner output into a web-friendly format
  • Replacing oversized .bmp screenshots with compact PNGs in docs and support tickets
  • Preparing bitmaps from embedded devices or old apps for use on a website or in a CMS
  • Adding image assets to a git repo without committing multi-megabyte raw bitmaps
  • Standardizing a folder of mixed image formats on PNG for consistent downstream tooling

Pro Tips

  • Flat-color images (screenshots, logos, diagrams) shrink the most; detailed photos compress less because PNG finds fewer repeated runs.
  • If your BMP refuses to load, re-save it from the source app as a standard 24-bit bitmap, since some old RLE or non-standard headers aren't browser-decodable.
  • Expecting a transparent background? It won't appear from an opaque BMP. Cut out the background in an image editor before or after converting.
  • For photos where lossless isn't essential, JPEG or WebP will be far smaller than PNG; reach for this only when exact pixels matter.
  • Very large bitmaps consume real memory during decode, so close other heavy tabs if a huge image stalls.
  • Keep the original BMP until you've confirmed the PNG looks right; since the conversion is lossless, the PNG is a safe drop-in once verified.

Frequently Asked Questions

Yes. Both formats store exact pixel data with no lossy compression, so every color value in your bitmap is preserved in the PNG. Only the file size changes, because PNG compresses data that BMP leaves raw. You can convert back to BMP later and get the same pixels, with no generational degradation.
Classic BMP is uncompressed: it stores 3 or 4 bytes per pixel with no attempt to pack repeated colors, so a 1920x1080 image is roughly 6 to 8 MB regardless of content. PNG runs DEFLATE over those same pixels, which is why screenshots, diagrams, and flat-color graphics shrink dramatically while detailed photos shrink far less.
Standard BMP files are opaque and carry no alpha, so there is nothing to preserve and the resulting PNG is opaque too. PNG itself supports a full alpha channel, but this converter won't fabricate transparency that wasn't in the source. For a transparent background, cut it out in an image editor before or after converting.
No. The conversion runs entirely in your browser using built-in image APIs. Your BMP is read into memory locally, decoded, and offered back as a download. Nothing is uploaded, stored, or seen by a server, which makes this safe for confidential scans, IDs, or internal screenshots.
No. Width, height, and every pixel color stay identical. The bitmap is drawn to a canvas at its native resolution and that exact raster is encoded as PNG. There is no resizing, recoloring, or quality slider, because lossless PNG has nothing to throw away. One detail: an indexed or grayscale BMP is written out as a truecolor PNG with the same pixel values, not a palette image.
This relies on your browser's native bitmap decoder, which handles the common 24-bit and 32-bit BMPs plus most 8-bit indexed and grayscale ones. Exotic or very old encodings (certain RLE-compressed or non-standard headers) that the browser can't decode will simply fail to load. If that happens, re-save the file from its source app as a standard 24-bit bitmap first.
It processes one file per conversion. Since everything runs locally and finishes near-instantly with no upload or queue, you can convert files back to back quickly. For a folder of hundreds, a desktop tool or ImageMagick script will be faster, but for a handful of bitmaps this is quicker than it sounds.
Convert to PNG when you need exact pixels: screenshots, UI mockups, line art, diagrams, and anything with text or sharp edges, where JPEG's lossy compression would smear edges into artifacts. For photographic content where pixel-perfect isn't required, JPEG or WebP will be much smaller. PNG is also universally supported, unlike BMP, which is patchy outside Windows and bloats page weight.