BMP to SIXEL Converter
FileFlip converts BMP to SIXEL entirely inside your browser, using ImageMagick compiled to WebAssembly. The file is never uploaded to a server: it is read off your disk, converted on your own machine, and saved back by the browser. That means no file-size limit, no queue and no account.
How do I convert a BMP file to SIXEL?#
- Drop your BMP file onto the converter at the top of this page, or click it to pick one from your computer. You can add as many as you like.
- Leave the target set to SIXEL and the conversion starts on its own. FileFlip downloads 14.1 MB of WebAssembly the first time and nothing after that, then runs ImageMagick on your own machine.
- Save the SIXEL file. Your browser writes it straight to your downloads folder, because there was never a server holding it.
Does converting BMP to SIXEL lose quality?#
No. Converting BMP to SIXEL writes the data out again without discarding any of it, so nothing that was in the BMP file is lost on the way. What changes is the size of the file, not what is inside it.
Is it safe to convert BMP files online?#
Yes, because nothing is uploaded. FileFlip converts BMP files inside the browser tab you already have open, using WebAssembly builds of the same engines a desktop converter would install. Your file is read from your own disk into the page's memory, and no request carrying it is ever made.
You do not have to take that on trust. Open your browser's network panel, run a conversion, and you will see the engine come down and your file go nowhere. There is no upload, no server-side copy, no retention window, and no account tied to what you converted.
How FileFlip works lists every engine, its version and its download size, and shows how to check for yourself that nothing leaves your machine.
What BMP to SIXEL actually does to the file#
Converting BMP to SIXEL runs on ImageMagick, downloads 14.1 MB of WebAssembly the first time and nothing after that, writes the data out again without discarding any of it, and drops transparency.
| Engine | ImageMagick |
|---|---|
| Conversion path | One step: BMP → SIXEL |
| Downloaded to your browser | 14.1 MB, once, then cached by your browser |
| Quality | Lossless |
| You get back | One file |
| Where it runs | In a background worker, so the page stays responsive |
What survives the conversion
| What is in the file | This conversion | Why |
|---|---|---|
| Transparency | Dropped | The target format has nowhere to put it. |
Worth knowing before you start:
- the target holds at most 256 colours, so a full-colour image is quantised to a palette
What is a BMP file?#
A BMP file holds a device-independent bitmap: a pixel grid stored with a Microsoft-defined header and, in the overwhelming majority of BMP files in the wild, no compression at all.
Use BMP when a Windows-native application, printer driver, or legacy tool specifically expects it, or when pixel data has to be stored with zero encoding overhead for a processing pipeline.
Convert BMP to PNG or JPEG for anything leaving that pipeline, since both produce a far smaller file and PNG matches BMP's lossless, generation-safe quality.
What is a SIXEL file?#
A SIXEL file holds a bitmap encoded entirely as printable ASCII characters, using DEC's six-pixel-tall encoding scheme, so it can be sent to a printer or terminal over a plain 7-bit serial link and displayed without any separate image protocol.
Use Sixel when an image needs to display inline inside a terminal session, such as showing a chart or a thumbnail over SSH without opening a separate viewer.
Convert a Sixel image to PNG once it needs to be viewed anywhere outside a terminal emulator that understands the encoding.
BMP to SIXEL questions people ask#
Why are BMP files so much bigger than JPEG or PNG?
Most BMP files store every pixel's color value directly with no compression, so a BMP is close in size to the raw uncompressed image data. JPEG and PNG both apply compression, lossy in JPEG's case and lossless in PNG's, which is why the same photo saved as either is a fraction of the size of a BMP.
Can a BMP file be compressed?
Yes, though it's rare in practice. The BMP specification includes run-length encoding modes, RLE8 for 8-bit images and RLE4 for 4-bit images, that compress losslessly the same way GIF's LZW does, just less efficiently. Almost all BMP files encountered in practice still use BI_RGB, the uncompressed mode, because that is what most software defaults to writing.
Does BMP support transparency?
It can, but support is inconsistent. The BITMAPV4HEADER and BITMAPV5HEADER, both extensions to the original format, can store a 32-bit image with an alpha channel, but many image viewers, browsers, and older software ignore that alpha data entirely and render the image as fully opaque. PNG's alpha transparency is much more reliably supported across software.
Is BMP the same thing as a DIB?
They're closely related. DIB, device-independent bitmap, is the internal Windows data structure of header, color table, and pixel data that a BMP file wraps in a short file header. The .dib extension is used for that same data saved without expecting the .bmp file header, which is why BMP and DIB are treated as aliases of the same format.